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Synthesis of functionalized 2-salicyloylfurans, furo[3,2-b]chromen-9-ones and 2-benzoyl-8H-thieno[2,3-b]indoles by one-pot cyclizations of 3-halochromones with ?-ketoamides and 1,3-dihydroindole-2-thiones.
Org. Biomol. Chem.
PUBLISHED: 11-11-2014
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Functionalized 2-salicyloylfurans and 2-benzoyl-8H-thieno[2,3-b]indoles were prepared under mild conditions by reaction of 3-halochromones with ?-ketoamides and 1,3-dihydroindole-2-thiones, correspondently. The subsequent oxidative cyclization of the products resulted in formation of the corresponding furo[3,2-b]chromen-9-ones. These molecules could also be directly prepared from 3-halochromones using a one-pot protocol. The cyclization reactions reported herein are mechanistically surprising as they proceed via the oxygen and not via the (more nucleophilic) nitrogen atom of the ?-ketoamide.
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Novel synthesis of 5-methyl-5,10-dihydroindolo[3,2-b]indoles by Pd-catalyzed C-C and two-fold C-N coupling reactions.
Org. Biomol. Chem.
PUBLISHED: 11-11-2014
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A series of 5,10-dihydroindolo[3,2-b]indoles was successfully prepared by an efficient two-step strategy based on site-selective Pd-catalyzed cross-coupling reaction with N-methyl-2,3-dibromoindole and subsequent cyclization by two-fold Pd-catalyzed C-N coupling with amines. The products show a strong fluorescence.
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A new class of azadipnictiridines generated by an unusual rearrangement reaction.
Inorg Chem
PUBLISHED: 10-20-2014
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Dipnictadiazanediyls, [E(?-NR)]2 (E = P, As), the pnictogen analogues of cyclobutandiyl, were found to react readily with alkynes forming [2.1.1]bicyclic structures. These, in turn, rearrange in an unprecedented reaction to [3.1.o]bicycles leading to the isolation of the first azadiarsiridine and the determination of its solid-state structure. All new species were comprehensively characterized, and the reaction pathways and bonding situations were computationally studied.
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A Mixed Arsenic-Phosphorus Centered Biradicaloid.
Angew. Chem. Int. Ed. Engl.
PUBLISHED: 08-28-2014
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Main-group singlet biradicaloids have been thoroughly investigated in the past two decades, especially derivatives of cyclobutane-1,3-diyl. However, in each of the known examples, the radical centers are identical. Therefore, we sought to prepare a mixed dipnictadiazanediyls with P and As bearing the radical character. To achieve this goal, the unprecedented cyclodichloro arsaphosphadiazane [ClP(?-NTer)2 AsCl] had to be prepared first. Treatment of [ClP(?-NTer)2 AsCl] with a halide-abstracting agent led to the novel cyclic cation [P(?-NTer)2 AsCl](+) , while reduction with magnesium afforded the first arsaphosphadiazanediyl [P(?-NTer)2 As].
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Dimers and trimers of diphosphenes: a wealth of cyclo-phosphanes.
Chemistry
PUBLISHED: 08-21-2014
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Various new P-based ring systems were synthesised by transferring established reaction routes from NP chemistry to the analogous PP compounds. Due to the different electronic situations of phosphorus and nitrogen with respect to s and p character of the lone pair, different reactivity of the phosphorus compounds was observed, especially with regard to the specificity of the reactions and the stability of the products. Whereas Mes*N?PCl (Mes*=2,4,6-tri-tert-butylphenyl) is stable in the solid state and in solution, the formal phosphorus congener Mes*P?PCl is highly reactive and could not be observed. Instead, several formal dimers and trimers of Mes*P?PCl could be isolated, which constitute an intriguing variety of three- and four-membered ring systems.
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Dinuclear Ru/Ni, Ir/Ni, and Ir/Pt complexes with bridging phenanthroline-5,6-dithiolate: synthesis, structure, and electrochemical and photophysical behavior.
Inorg Chem
PUBLISHED: 08-20-2014
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We report the synthesis and full characterization of dinuclear complexes with the bridging ligand phenanthroline-5,6-dithiolate (phendt(2-)) featuring the [Ru(bpy)2](2+) or Ir(ppy)2](+) fragment at the diimine donor center and the [Ni(dppe)](2+) or [Pt(phen)](2+) complex moiety at the dithiolate group. The molecular structures of the mononuclear complexes [(C5H5)2Ti(S,S'-phendt)] and [(ppy)2Ir{N,N'-phendt-(C2H4CN)2}](PF6) as well as the dinuclear complex [(C5H5)(PPh3)Ru(phendt)Ni(dppe)](PF6) determined by X-ray diffraction (XRD) studies are compared. Photophysical studies with mononuclear [(bpy)2Ru{phendt-(C2H4CN)2}](2+) and [(ppy)2Ir{phendt-(C2H4CN)2}](+) as well as dinuclear [(bpy)2Ru(phendt)Ni(dppe)](2+) and [(ppy)2Ir(phendt)Ni(dppe)](+) uncovered an effective luminescence quenching in the dinuclear complexes. Lifetime measurements at room temperature, steady-state measurements at low temperature, electrochemical investigations, and DFT calculations provide evidence for a very efficient energy transfer from the Ru/Ir to the Ni complex moiety with a rate constant k > 5 × 10(9) s(-1). In comparison, the [Ru]phendt[Ni] complex displays a higher quenching efficiency with reduced excited state lifetime, whereas the [Ir]phendt[Ni] complex is characterized by an unaltered lifetime of the thermally equilibrated excited state.
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Palladium catalyzed synthesis and physical properties of indolo[2,3-b]quinoxalines.
Org. Biomol. Chem.
PUBLISHED: 07-08-2014
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A series of indolo[2,3-b]quinoxaline derivatives were efficiently synthesized from 2,3-dibromoquinoxaline by two pathways. A one-pot approach using Pd-catalyzed two-fold C-N coupling and C-H activation reactions gave indolo[2,3-b]quinoxaline derivatives in good yields, but with limited substrate scope. In addition, a two-step approach to indolo[2,3-b]quinoxalines was developed which is based on Pd-catalyzed Suzuki coupling reactions and subsequent annulation by Pd-catalyzed two-fold C-N coupling with aromatic and aliphatic amines. The electrochemical and photochemical properties of indolo[2,3-b]quinoxaline derivatives were investigated. These studies show that 6-(4-methoxyphenyl)-6H-indolo[2,3-b]quinoxaline showed the highest HOMO energy level and lowest band gap.
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Activation of small molecules by phosphorus biradicaloids.
Chemistry
PUBLISHED: 06-14-2014
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The reactivity of biradicaloid [P(?-NTer)]2 was employed to activate small molecules bearing single, double, and triple bonds. Addition of chalcogens (O2 , S8 , Sex and Tex ) led to the formation of dichalcogen-bridged P2 N2 heterocycles, except from the reaction with molecular oxygen, which gave a P2 N2 ring featuring a dicoordinated P(III) and a four-coordinated P(V) center. In formal [2?e+2?e] addition reactions, small unsaturated compounds such as ethylene, acetylene, acetone, acetonitrile, tolane, diphenylcarbodiimide, and bis(trimethylsilyl)sulfurdiimide are readily added to the P2 N2 heterocycle of the biradicaloid [P(?-NTer)]2 , yielding novel heteroatom cage compounds. The synthesis, reactivity, and bonding of the biradicaloid [P(?-NTer)]2 were studied in detail as well as the synthesis, properties, and structural features of all addition products.
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Synthesis, structure, and reactivity of diazene adducts: isolation of iso-diazene stabilized as a borane adduct.
Chemistry
PUBLISHED: 04-02-2014
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This work describes the synthesis and full characterization of a series of GaCl3 and B(C6 F5 )3 adducts of diazenes R(1) ?N?N?R(2) (R(1) =R(2) =Me3 Si, Ph; R(1) =Me3 Si, R(2) =Ph). Trans-Ph?N?N?Ph forms a stable adduct with GaCl3 , whereas no adduct, but instead a frustrated Lewis acid-base pair is formed with B(C6 F5 )3 . The cis-Ph?N?N?Ph?B(C6 F5 )3 adduct could only be isolated when UV light was used, which triggers the isomerization from trans- to cis-Ph?N?N?Ph, which provides more space for the bulky borane. Treatment of trans-Ph?N?N?SiMe3 with GaCl3 led to the expected trans-Ph?N?N?SiMe3 ?GaCl3 adduct but the reaction with B(C6 F5 )3 triggered a 1,2-Me3 Si shift, which resulted in the formation of a highly labile iso-diazene, Me3 Si(Ph)N?N; stabilized as a B(C6 F5 )3 adduct. Trans-Me3 Si?N?N?SiMe3 forms a labile cis-Me3 Si?N?N?SiMe3 ?B(C6 F5 )3 adduct, which isomerizes to give the transient iso-diazene species (Me3 Si)2 N?N?B(C6 F5 )3 upon heating. Both iso-diazene species insert easily into one B?C bond of B(C6 F5 )3 to afford hydrazinoboranes. All new compounds were fully characterized by means of X-ray crystallography, vibrational spectroscopy, CHN analysis, and NMR spectroscopy. All compounds were further investigated by DFT and the bonding situation was assessed by natural bond orbital (NBO) analysis.
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Regioselective and guided C-H activation of 4-nitropyrazoles.
J. Org. Chem.
PUBLISHED: 03-24-2014
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A divergent and regioselective approach to 5-aryl-4-nitro-1H-pyrazoles was developed by guided transition-metal-catalyzed arylation of 4-nitro-1H-pyrazoles. This method provides a convenient tool for the functionalization of the pharmacologically relevant pyrazole scaffold. The scope and limitations of the methodology were studied.
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Azidophosphenium cations: versatile reagents in inorganic synthesis.
Inorg Chem
PUBLISHED: 03-21-2014
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This work describes the synthesis and characterization of a series of iminophosphorane-substituted phosphenium cations of the type [R2NPNP(Cl)2NPNR'2][GaCl4] [R = iPr; R' = iPr (7[GaCl4]), SiMe3 (8)], which are directly derived from azidophosphenium salt [iPrNPN3][GaCl4] (2iPr[GaCl4]) and the corresponding chlorophosphane R2NPCl2. The reactivity of 7[GaCl4] toward 2,3-dimethylbutadiene (dmb) and 2,2'-bipyridine (bipy) was investigated, resulting in the formation of 7-dmb[GaCl4] and 7-Cl. In addition, self-condensation of [(Me3Si)2NPN3][GaCl4] (2SiMe3[GaCl4]) was studied in detail, and [(Me3Si)2NPNP(XY)N(SiMe3)2][GaCl4] [X = Cl; Y = Cl (13), N3 (14)] were determined as products on the basis of (31)P NMR spectroscopy. The reaction of 2SiMe3[GaCl4] with [(Me3Si)2NPCl][GaCl4] (1SiMe3[GaCl4]) yielded an unprecedented bicyclic 1,3,2?(3),4?(5)-diazadiphosphetidine (15), which was formed via a GaCl3-assisted Me3SiCl elimination starting from 13. Furthermore, cations of the type [R2NPNPR'3][GaCl4] [R = iPr; R' = cHex (19)] were obtained by the effective combination of 2R[GaCl4] (R = iPr, SiMe3) with PR'3 (R' = Ph, cHex). Azidochlorophosphanes R2NP(N3)Cl [R = iPr, SiMe3 (20R)] are shown to be accessible when 2R[GaCl4] was combined with bipy. All new compounds were fully characterized by means of X-ray, vibrational spectroscopy, CHN analysis, and NMR experiments. All compounds were further investigated by means of density functional theory, and the bonding situation was accessed by natural bond orbital analysis.
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Efficient synthesis of biscarbazoles by palladium-catalyzed twofold C-N coupling and C-H activation reactions.
Org. Biomol. Chem.
PUBLISHED: 03-14-2014
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A new and efficient strategy for the synthesis of 3,9'- and 2,9'-biscarbazoles was developed. Our strategy relies on the cyclization of 1,1'-biphenyl-2,2'-diyl bis(trifluoromethanesulfonate) with 4- or 3-anisidine, transformation of the methoxy to a triflate group and subsequent oxidative Pd-catalyzed cyclization with various anilines.
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The reactivity of silylated amino(dichloro)phosphanes in the presence of silver salts.
Inorg Chem
PUBLISHED: 02-21-2014
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New cyclic and acylic phosphorus-nitrogen compounds have been synthesized in reactions of Hyp-N(SiMe3)PCl2 (hypersilyl = Hyp = (Me3Si)3Si) with silver salts of the perfluorinated anions [CF3CO2](-), [CF3SO3](-), and [C6F5](-). Depending on the choice of the silver salt, not only AgCl but also Me3SiCl elimination could be observed, leading to a transient highly reactive 1,3 dipole molecule. This 1,3 dipole molecule was found to be a key species, which can undergo [3 + 2] cyclization, when a dipolarophile such as acetonitrile is present. Also, dimerization or even cyclo-tetramerization are observed. The occurrence of different reaction channels demonstrates that the hypersilyl moiety can act as a highly reactive functional group. All new compounds have been characterized by single-crystal X-ray diffraction studies.
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Isolation of a labile homoleptic diazenium cation.
Angew. Chem. Int. Ed. Engl.
PUBLISHED: 02-14-2014
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Following our interest in nitrogen chemistry, we now describe the synthesis, structure, and bonding of labile disilylated diazene, its GaCl3 adduct, and the intriguing trisilylated diazenium ion [(Me3 Si)2 N?N-SiMe3 ](+), a dark blue and highly labile (Tdecomp >-30?°C) homoleptic cation of the type [R3 N2 ](+). Although direct silylation of Me3 Si-N=N-SiMe3 failed, the [(Me3 Si)2 N=N-SiMe3](+) ion was generated in a straightforward two-electron oxidation reaction from mercury(II) dihydrazide and Ag[GaCl4]. Moreover, previous structure data of Me3 Si-N?N-SiMe3 were revised on the basis of new data.
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New P-N cage compounds generated by small-molecule activation.
Chemistry
PUBLISHED: 01-13-2014
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The isolation of new small-cage compounds consisting exclusively of Group?15 elements was achieved by exploiting the reactivity of diphosphadiazanediyls. These biradicaloids were used to activate small molecules containing double bonds, such as diazenes and in situ generated diphosphenes, leading to the formation of hexapnicta-[2.1.1]bicyclohexanes.
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Synthesis of 1,3-dichloro-cyclo-1,3-diphosphadiazanes from silylated amino(dichloro)phosphanes.
Inorg Chem
PUBLISHED: 09-23-2013
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The synthesis of 1,3-dichloro-cyclo-1,3-diphosphadiazanes [ClP(?-NR)]2 via elimination of Me3SiCl from silylated amino(dichloro)phosphanes, R-N(SiMe3)PCl2, was studied by different synthetic protocols starting from R-N(H)SiMe3 (R = Si(SiMe3)3 = Hyp, N(SiMe3)2, Mes* = 2,4,6-tri-tert-butylphenyl, Ter = 2,4-bis(2,4,6-trimethylphenyl)phenyl, Dipp = 2,6-diisopropylphenyl, Dmp =2,6-dimethylphenyl, Ad = Adamantyl, Trityl = Ph3C, Tos = tosyl = CH3C6H4SO2, n-Oct = n-octyl, and Me3Si). A new synthetic route using trimethylsilyl-substituted amino(dichloro)phosphanes, R-N(SiMe3)PCl2, was developed to form cyclo-diphosph(III)-azanes simply by adding a mixture of R(f)OH/base (R(f)OH = hexafluoroisopropanole). By this method electron-rich/-poor aryl-, silyl-, and bissilylamino-substituted cyclo-diphosph(III)-azanes are accessible such as the unprecedented (Me3Si)2N-substituted species [ClP(?-NN(SiMe3)2)]2 starting from tris(trimethylsilyl)hydrazine and PCl3. Additionally, the difficulties with the preparation of cyclo-diphosphadiazanes depending on the starting materials, solvents, and bases due to the competition of different reaction channels are studied.
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Synthesis and reactivity of 5-polyfluoroalkyl-5-deazaalloxazines.
Org. Biomol. Chem.
PUBLISHED: 07-13-2013
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Reaction of 6-arylamino-1,3-dialkyluracils with anhydrides of polyfluorocarboxylic acids in the presence of pyridine and subsequent cyclization with concentrated H2SO4 gave the corresponding 1,3-dialkyl-5-(polyfluoroalkyl)pyrimido[4,5-b]quinoline-2,4(1H,3H)-diones (5-polyfluoroalkyl-5-deazaalloxazines). The reactivity of these compounds towards nucleophilic reagents, such as sodium cyanoborohydride, acetophenone, nitromethane, potassium cyanide, indole and p-thiocresol, as well as Suzuki and Sonogashira couplings are described. The nucleophilic addition takes place at the 5-position of the 5-deazaalloxazine system and is in many cases irreversible to give 5,10-dihydropyrimido[4,5-b]quinoline-2,4(1H,3H)-dione derivatives in good to excellent yields.
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Mercury Azides and the Azide of Millons Base.
Angew. Chem. Int. Ed. Engl.
PUBLISHED: 06-27-2013
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Always look on the bright azide of life: The synthesis of Millons base azido salt [Hg2 N]N3 , and the metastable ?-Hg(N3 )2 , along with their full characterization is possible for the first time and closes an open gap in azide chemistry.
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Structure and bonding of novel acyclic bisaminoarsenium cations.
Inorg Chem
PUBLISHED: 06-17-2013
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The synthesis and characterization of a salt bearing a labile bisaminoarsenium cation of the type {[(Me3Si)2N]2As}(+) (9a) are described, which was obtained in the reaction of the chloroarsane [(Me3Si)2N]2AsCl (8) with GaCl3. Reacting 8 with AgOTf did not yield an arsenium salt, but the cyclo-diarsadiazane [(Me3Si)2NAs-?-NSiMe3]2 (11) was obtained in excellent yields. Moreover, the reactivity of the analogous antimony species [(Me3Si)2N]2SbCl (12) was studied. In the reaction with GaCl3, the aminochlorostibenium salt [(Me3Si)2NSbCl](+)[(Me3Si)2N(GaCl3)2](-) (5) was isolated. In the reaction with AgOTf, substitution of the chlorine in 12 resulted in the formation of [(Me3Si)2N]2SbOTf (13), a compound with significant stibenium character. All new compounds have been fully characterized by means of X-ray, vibrational spectroscopy, CHN analysis, and NMR experiments. All compounds were further investigated by means of density functional theory and the bonding situation was accessed by natural bond orbital (NBO) analysis.
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Solid state structure of Bi(N3)3, Bi(N3)3·solvates and the structural dynamics in the [Bi(N3)6]3- anion.
Inorg Chem
PUBLISHED: 05-09-2013
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The highly explosive bismuth triazide, Bi(N3)3, was obtained in pure form by the reaction of BiF3 with Me3SiN3 in acetonitrile under solvothermal conditions at temperatures between 90 and 100 °C. X-ray, (14)N NMR, infrared, and Raman spectra are discussed along with the data for the acetonitrile, acetone, and dmso adducts. The influence of the solvent on the purity of the azide products is studied in detail for Bi(N3)3 and the [Bi(N3)6](3-) ion. Moreover, temperature dependent structural dynamics in the [Bi(N3)6](3-) ion, which is caused by small changes in the local environment around the [Bi(N3)6](3-) ion in the solid state, was studied by temperature variable single crystal X-ray and Raman studies. The azido-chlorido ligand back exchange was studied in detail by NMR techniques in [Bi(N3)6](3-) and Bi(N3)3 when chlorinated solvents such as CH2Cl2 were utilized leading to the formation of CH2(N3)Cl and/or HN3 along with partially chlorinated bismuth azides.
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On the synthesis and reactivity of highly labile pseudohalogen phosphenium ions.
Inorg Chem
PUBLISHED: 04-24-2013
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The synthesis and characterization of salts bearing highly labile pseudohalogen-substituted aminophosphenium cations of the type [(Me3Si)2NPX][GaCl4] (X = NCO, NCS, O(SiMe3)) and their respective reactivity toward Lewis bases (4-dimethylaminopyridine, dmap) and dienes (2,3-dimethyl-1,3-butadiene, dmb; 1,3-cyclo-hexadiene, chd) are described. As ?-acidic species, aminophosphenium cations react with dmap at low temperatures to yield adduct salts of the type [(Me3Si)2NP(dmap)X][GaCl4] (X = Cl, N3, NCO) which were fully characterized. In the reaction with dienes at -50 °C, salts bearing phospholenium cations were obtained that could be structurally characterized. The crystal structures of novel 7-phosphanorbornenium cations of the type [(Me3Si)2NP(C6H8)X][GaCl4] (X = Cl, N3, NCO) are reported. All compounds were further investigated by means of density functional theory, and the bonding situation was accessed by Natural Bond Orbital (NBO) analysis.
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Acetylene dithiolate linking up the [TpW(CO)(CN)] moiety with Ru(II) or Pd(II.).
Chemistry
PUBLISHED: 03-28-2013
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A series of heterodinuclear complexes with acetylene dithiolate (acdt(2-) ) as the bridging moiety were synthesised by a facile one-pot procedure that avoided use of the highly elusive acetylene dithiol. Generation of the W-Ru complex [TpW(CN)(CO)(C2 S2 )Ru(?(5) -C5 H5 )(PPh3 )] (Tp=hydrotris(3,5-dimethylpyrazolyl)borate) and the W-Pd complexes [TpW(CN)(CO)(C2 S2 )Pd(dppe)] and [TpW(CO)2 (C2 S2 )Pd(dppe)][PF6 ] (dppe=1,2-bis(diphenylphoshino)ethane), which exhibit a [W(?(2) -?(2) -C2 S2 )M] core (M=Ru, Pd), was accomplished by using a transition-metal-assisted solvolytical removal of the Me3 Si-ethyl thiol protecting groups. All intermediate species of the reaction have been fully characterised. The highly coloured W-Ru complex [TpW(CN)(CO)(C2 S2 )Ru(?(5) -C5 H5 )(PPh3 )] shows reversible redox chemistry, as does the prototype complex [TpW(CO)2 (C2 S2 )Ru(?(5) -C5 H5 )(PPh3 )][PF6 ]. Single crystal X-ray diffraction and IR, EPR and UV/Vis spectroscopic studies in conjunction with DFT calculations prove the high electronic delocalisation of states over the acdt(2-) linker. Comparative studies revealed a higher donor strength and more pronounced dithiolate character of acdt(2-) in [TpW(CN)(CO)(C2 S2 )Ru(?(5) -C5 H5 )(PPh3 )] relative to [TpW(CO)2 (C2 S2 )Ru(?(5) -C5 H5 )(PPh3 )](+) . In addition, the influence of the overall complex charge on the metric parameters was investigated by single-crystal X-ray diffraction studies with the W-Pd complexes [TpWL2 (C2 S2 )Pd(dppe)] (L=(CN(-) )(CO) or (CO)2 ). The central [W(C2 S2 )Pd] units exhibit high structural similarity, which indicates the extensive delocalisation of charge over both metals.
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Synthesis of N,N-diglycosylated isoindigos.
Org. Biomol. Chem.
PUBLISHED: 01-04-2013
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The first N,N-diglycosylated isoindigos were prepared by P(NEt(2))(3)-mediated dimerization of acetyl protected N-glycosyl-5-alkylisatins. Subsequent deacetylation yielded the corresponding deprotected N,N-diglycosylated isoindigos. Isatine-N-glycosides containing an unsubstituted or alkyl-substituted heterocyclic moiety and ?-D-manno- and ?-L-rhamno configured carbohydrate substituents were successfully transformed into the corresponding isoindigos. In contrast, isatins with ?-D-gluco- or ?-D-xylo configured substituents failed to give the desired products.
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Tandem dinucleophilic cyclization of cyclohexane-1,3-diones with pyridinium salts.
Beilstein J Org Chem
PUBLISHED: 01-01-2013
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The cyclization of cyclohexane-1,3-diones with various substituted pyridinium salts afforded functionalized 8-oxa-10-aza-tricyclo[7.3.1.0(2,7)]trideca-2(7),11-dienes. The reaction proceeds by regioselective attack of the central carbon atom of the 1,3-dicarbonyl unit to 4-position of the pyridinium salt and subsequent cyclization by base-assisted proton migration and nucleophilic addition of the oxygen atom to the 2-position, as was elucidated by DFT computations. Fairly extensive screening of bases and additives revealed that the presence of potassium cations is essential for formation of the product.
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2,3-unsubstituted chromones and their enaminone precursors as versatile reagents for the synthesis of fused pyridines.
Org. Biomol. Chem.
PUBLISHED: 12-12-2011
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A divergent and regioselective approach to fused pyridines was developed through formal [3 + 3] cyclocondensations from simple 2,3-unsubstituted chromones or their enaminone precursors.
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Silylium-arene adducts: an experimental and theoretical study.
J. Am. Chem. Soc.
PUBLISHED: 12-06-2011
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The solvent-coordinated [Me(3)Si·arene][B(C(6)F(5))(4)] salts (arene = benzene, toluene, ethylbenzene, n-propylbenzene, isopropylbenzene, o-xylene, m-xylene, p-xylene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene) are prepared and fully characterized. As an interesting decomposition product the formation of bissilylated fluoronium ion [Me(3)Si-F-SiMe(3)](+) was observed and even cocrystallized with [Me(3)Si·arene][B(C(6)F(5))(4)] (arene = benzene and toluene). Investigation of the degradation of [Me(3)Si·arene][B(C(6)F(5))(4)] reveals the formation of fluoronium salt [Me(3)Si-F-SiMe(3)][B(C(6)F(5))(4)], B(C(6)F(5))(3), and a reactive "C(6)F(4)" species which could be trapped with CS(2). Upon addition of CS(2), the formation of a formal S-heterocyclic carbene adduct, C(6)F(4)CS(2)-B(C(6)F(5))(3), was observed. The structure and bonding of substituted [Me(3)Si·arene][B(C(6)F(5))(4)] with arene = R(n)C(6)H(6-n) (R = H, Me, Et, Pr, and Bu; n = 0-6) is discussed on the basis of experimental and theoretical data. X-ray data of [Me(3)Si·arene][B(C(6)F(5))(4)] salts reveal nonplanar arene species with significant cation···anion interactions. As shown by different theoretical approaches (charge transfer, partial charges, trimethylsilyl affinity values) stabilizing inductive effects occur; however, the magnitude of such effects differs depending on the degree of substitution and the substitution pattern.
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Ethenedithione (S=C=C=S): trapping and isomerization in a cobalt complex.
Angew. Chem. Int. Ed. Engl.
PUBLISHED: 07-19-2011
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Swing bridge: The triplet species ethenedithione has been generated within the coordination sphere of cobalt, leading to a dinuclear ?-?(2)-?(2)-C(2)S(2) complex (see picture: C?gray, Co?blue, P?purple, S?yellow). Depending on the solvent, the C(2)S(2) moiety displays a transoid or a cisoid geometry. This isomerization step changes the sign of the magnetic coupling between the cobalt centers.
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Ethyl 4-chloro-2-fluoro-3-hy-droxy-5-methyl-biphenyl-2-carboxyl-ate.
Acta Crystallogr Sect E Struct Rep Online
PUBLISHED: 07-18-2011
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In the title compound, C(16)H(14)ClFO(3), the dihedral angle between the mean planes of the two benzene rings is 71.50?(5)°. Due to an intra-molecular O-H?O hydrogen bond between the hy-droxy group and the carbonyl O atom of the ethyl ester group, the ethyl ester group lies within the ring plane. The crystal structure is consolidated by inter-molecular C-H?O and C-H?F inter-actions.
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Ionic liquids containing the triply negatively charged tricyanomelaminate anion and a B(C6F5)3 adduct anion.
Chemistry
PUBLISHED: 06-23-2011
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Room-temperature ionic liquids containing the triply charged tricyanomelaminate (tcmel) ion [C(3)N(6)(CN)(3)](3-) were synthesized. The 1-methyl-3-methylimidazolium (MMIm), 1-ethyl-3-methylimidazolium (EMIm), and 1-butyl-3-methylimidazolium (BMIm) salts of the tricyanomelaminate ion have glass transition temperatures (-6, -20, and -30 °C) similar to those found for the analogous monomeric dicyanoamide salts. They are thermally stable up to over 200 °C and dissolve in polar organic solvents. Addition of B(C(6)F(5))(3) to M(3) [tcmel] (M=Na, MMIm, EMIm, BMIm) yields salts containing the very voluminous adduct ion [C(3)N(6) {CN·B(C(6)F(5))(3)}(3)](3-) (tcmel_3B). The solid-state structure of [MMIm](3-) [tcmel] shows only long cation···anion contacts but in large number, while the solid-state structure of [Na(THF)(3)](3-) [tcmel_3B]·1.76 THF displays strong interactions of the sodium cation with the amido nitrogen atoms of the anion. Hence this adduct anion cannot be regarded as a weakly coordinating anion. A similar situation is found for the MMIm salt, [MMIm](3) [tcmel_3B]·2.66?CH(2)Cl(2), in which weak hydrogen bonds with the acidic proton of the MMIm ion are observed. On the basis of computations the energetics, structural trends, and charge transfer of adduct anion formation were studied.
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Synthesis and characterization of bis-cyclopropanated 1,3,5-tricarbonyl compounds. A combined synthetic, spectroscopic and theoretical study.
Org. Biomol. Chem.
PUBLISHED: 06-03-2011
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Bis-cyclopropanated 1,3,5-tricarbonyl compounds were prepared by a sequence of Claisen condensations and cyclopropanations. The optimization of the conditions proved to be very important to suppress retro-Claisen reactions. The conformation of these molecules was studied by experimental and computational methods. The syn/syn;syn/syn conformation is present for all derivatives. It is exclusively present in the case of the derivative containing a phenyl group located at the terminal carbon atom. In most cases, equilibria with other conformers are found.
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Synthesis of blue imino(pentafluorophenyl)phosphane.
Inorg Chem
PUBLISHED: 05-25-2011
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The reaction of AgC(6)F(5) with monomeric iminophosphanes of Mes*-N?P-X (X = Cl, I) in CH(2)Cl(2) at ambient temperature gives imino(pentafluorophenyl)phosphane, Mes*N?P(C(6)F(5)) (1), in almost quantitative yield (96%), which could be isolated as a highly viscous blue oil. The same reaction with LiC(6)F(5) results in the formation of imino(amino)phosphane (C(6)F(5))(2)P-N(Mes*)-P?NMes* (2) (yield 93%). In the second series of experiments the analogous reaction of MC(6)F(5) (M = Ag, Li) with dimeric [Cl-P(?-N-Dipp)](2) was studied, leading to the formation of [R-P(?-N-Dipp)](2) (R = C(6)F(5)) (3) for M = Ag, while only decomposition products such as P(C(6)F(5))(3) were observed in the reaction with the Li salt. Highly labile Mes*-N?P-C(6)F(5) (1) decomposes at ambient temperatures, forming among other products the diphosphane (C(6)F(5))(2)P-P(C(6)F(5))(2) (4). Reaction of 1 with Fe(2)(CO)(9) yields the iron carbonyl complexes Mes*-N?P(C(6)F(5))·Fe(CO)(4) (5) and [Mes*-N?P(C(6)F(5))](2)·Fe(CO)(3) (6). The structure, bonding, and potential energy surface are discussed on the basis of B3LYP/6-31G(d,p) computations. According to time-dependent B3LYP calculations, the blue color of 1 arises from an n ? ?* electronic transition.
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Synthesis of fluorinated purine and 1-deazapurine glycosides as potential inhibitors of adenosine deaminase.
J. Org. Chem.
PUBLISHED: 03-23-2011
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The synthesis of 2- and 6-trifluoromethylated purines and 1-deazapurines was performed by formal [3 + 3]-cyclization reactions of 5-aminoimidazoles with a set of trifluoromethyl-substituted 1,3-CCC- and 1,3-CNC-dielectrophiles. The corresponding fluorinated nucleosides were synthesized by glycosylation of 9-unsubstituted purines and 1-deazapurines with peracetylated ?-ribose, ?-glucose, and rhamnose and subsequent deprotection. These scaffolds can be considered as potential inhibitors of adenosine deaminase (ADA) and inosine monophosphate dehydrogenase (IMPDH) enzymes.
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Reactions of group 4 metallocene alkyne complexes with carbodiimides: experimental and theoretical studies of the structure and bonding of five-membered hetero-metallacycloallenes.
J. Am. Chem. Soc.
PUBLISHED: 03-17-2011
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The reaction of the low-valent metallocene(II) sources Cp(2)Ti(?(2)-Me(3)SiC(2)SiMe(3)) (7) and Cp(2)Zr(py)(?(2)-Me(3)SiC(2)SiMe(3)) (11, Cp = ?(5)-cyclopentadienyl, py = pyridine) with carbodiimides RN?C?NR (R = Cy, i-Pr, p-Tol) leads to the formation of five membered hetero-metallacycloallenes Cp(2)M{Me(3)SiC?C?C[N(SiMe(3))(R)]-N(R)} (9M-R) (M = Ti, R = i-Pr; M = Zr, R = Cy, i-Pr, p-Tol). Elimination of the alkyne (as the hitherto known reactivity of titanocene and zirconocene alkyne complexes would suggest) was not observed. The molecular structures of the obtained complexes were confirmed by X-ray studies. Moreover, the structure and bonding of the complexes 9Zr-Cy and 9Zr-p-Tol was investigated by DFT calculations.
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Multiple sonogashira reactions of polychlorinated molecules. Synthesis and photophysical properties of the first pentaalkynylpyridines.
Org. Lett.
PUBLISHED: 02-28-2011
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Hitherto unknown pentaalkynylpyridines have been prepared in high yields by Sonogashira cross-coupling reactions of pentachloropyridine. Their photophysical properties were studied and compared to those of penta- and hexaalkynylbenzenes which were efficiently prepared by the first Sonogashira reactions of pentachlorobenzene and hexachlorobenzene. The pentaalkynylpyridines show promising fluorescence properties because of their high quantum yields.
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Lewis acid assisted methyl/chlorine exchange in silylated hydrazinochlorophosphanes.
Inorg Chem
PUBLISHED: 02-22-2011
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Differently substituted hydrazinophosphanes of the type (Me(3)Si)(2)N-N(SiMe(3))-PR(1)R(2) (R(1) = Cl with R(2) = Me, C(6)F(5) and R(1) = Me, R(2) = C(6)H(5)) have been studied in the reaction with Lewis acids such as ECl(3) (E = Al, Ga). For (Me(3)Si)(2)N-N(SiMe(3))-P(Cl)(Me) and (Me(3)Si)(2)N-N(SiMe(3))-P(Me)(C(6)H(5)), only adduct formation was found while a chlorine/methyl exchange reaction was observed for (Me(3)Si)(2)N-N(SiMe(3))-P(Cl)R (R = C(6)H(5) and C(6)F(5)) leading to the formation of (Me(2)ClSi)(Me(3)Si)N-N(SiMe(3))-P(Me)R, which crystallize as ECl(3) adducts. The free hydrazinophosphanes can be obtained by removal of the Lewis acid with the help of a strong base such as 4-(dimethylamino)pyridine (DMAP).
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Synthesis of highly functionalized biaryls by condensation of 2-fluoro-1,3-bis(silyloxy) 1,3-dienes with 3-cyanochromones and subsequent domino "retro-Michael/aldol/fragmentation".
J. Org. Chem.
PUBLISHED: 11-09-2010
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The Me(3)SiOTf-mediated condensation of 1-ethoxy-2-fluoro-1,3-bis(trimethylsilyloxy) 1,3-dienes with 3-cyanochromones afforded 3-cyano-2-(4-ethoxy-3-fluoro-2,4-dioxobutyl)chroman-4-ones. Their reaction with triethylamine afforded fluorinated azaxanthones or biaryls. The product distribution depends on the structure of the diene. The formation of the biaryls can be explained by an unprecedented domino "retro-Michael/aldol/fragmentation" reaction.
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3-Methoxalylchromone--a novel versatile reagent for the regioselective purine isostere synthesis.
Org. Biomol. Chem.
PUBLISHED: 10-11-2010
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The first synthesis of 3-methoxalylchromone was described. The reaction of the latter with electron-rich aminoheterocycles afforded a set of heteroannelated pyridines bearing a CO(2)Me substituent located at the ?-position of the pyridine core.
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Synthesis of sterically encumbered 2,4-bis-m-terphenyl-1,3-dichloro-2,4-cyclo-dipnictadiazanes [m-TerNPnCl](2), (Pn = P, As).
Dalton Trans
PUBLISHED: 09-15-2010
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The reaction of m-terphenyl amine (2,6-bis-(2,4,6-trimethylphenyl)aniline, m-Ter = m-terphenyl = 2,6-bis-(2,4,6-trimethylphenyl)) and ECl(3) (E = P, As) in the presence of different bases (Et(3)N, n-BuLi, LDA, DBU) and under different reaction conditions was studied. The reaction with excess Et(3)N yielded m-Ter-N(H)-AsCl(2) for E = As, while for E = P m-Ter-N(PCl(2))(2) was formed. m-Ter-N(H)-ECl(2) was obtained in the reaction of m-terphenyl amine with n-BuLi and ECl(3) for E = As and P. Further treatment of m-Ter-N(H)-PCl(2) with Et(3)N led to the formation of 1,3-dichloro-cyclo-1,3-diphospha-2,4-diazane, a synthesis protocol which cannot be applied to the analogous arsenic species. 1,3-dichloro-cyclo-1,3-diarsa-2,4-diazane was isolated when DBU was added to m-Ter-N(H)-AsCl(2) at low temperature (-80 °C).
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Pseudohalonium ions: [Me3Si-X-SiMe3]+ (X=CN, OCN, SCN, and NNN).
Chemistry
PUBLISHED: 05-13-2010
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By utilizing reaction mixtures, such as Me(3)Si-X/[Me(3)Si-X-SiMe(3)](+) (X=CN, OCN, SCN, and NNN), it was possible to prepare the first examples of bissilylated pseudohalonium cations in high yields. The structure and bonding of a whole series of salts containing pseudohalonium cations is discussed on the basis of experimentally observed (X-ray diffraction, Raman, and IR spectroscopy, and mass spectrometry) and theoretically obtained data. Salts containing pseudohalonium cations are only stable in the presence of weakly coordinating anions, such as the well-known tetrakis(pentafluorophenyl)borate, [B(C(6)F(5))(4)](-).
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Preparation and characterization of [CF3SO3(SiMe3)2]+[B(C6F5)4]-.
Chem. Commun. (Camb.)
PUBLISHED: 04-14-2010
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Using tetrakis(pentafluorophenyl)borate, [B(C(6)F(5))(4)](-), as weakly coordinating counterion, the bis(trimethylsilyl)trifluoromethylsulfonium cation, [CF(3)SO(3)(Me(3)Si)(2)](+), is readily isolated for X-ray, NMR and IR structural characterization.
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Hypersilylated cyclodiphosphadiazanes and cyclodiphosphadiazenium salts.
Dalton Trans
PUBLISHED: 09-07-2009
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Starting from tris(trimethylsilyl)silane the novel 2-chloro-3,4-bis-tris(trimethylsilyl)silyl-cyclo-diphospha-diazenium-tetrachloridogallate salt (7) was prepared in a six step synthetic procedure including the synthesis of N-tris(trimethylsilyl)silyl-aminodichlorophosphine (4) and 1,3-dichloro-2,4-bis-tris(trimethylsilyl)silyl-cyclo-diphospha-diazane (5). All intermediate products along the reaction path have been isolated and fully characterized. The thermally stable cyclo-diphospha-diazenium-tetrachloridogallate (7) represents an interesting example of a binary cyclic P(III)/N four-membered heterocyclic cation, with a di- and tricoordinated P atom and a delocalized bond along the NP(+)N unit. The structures of all compounds are discussed on the basis of experimental X-ray data. Moreover, for comparison the hitherto unknown 1-chloro-3-trifluoromethanesulfonato-2,4-bis-tris(trimethylsilyl)silyl-cyclo-diphosphadiazane (6) has been synthesized and fully characterized.
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Methyl 5-chloro-2-hydr-oxy-3-(4-methoxy-phen-yl)-4,6-dimethyl-benzoate.
Acta Crystallogr Sect E Struct Rep Online
PUBLISHED: 07-23-2009
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In the title compound, C(17)H(17)ClO(4), the dihedral angle between the mean planes of the two benzene rings is 65.92?(5)°. The methyl ester group lies within the ring plane [deviations of O atoms from the plane = -0.051?(2) and 0.151?(2)?Å] due to an intra-molecular O-H?O hydrogen bond. In the crystal, mol-ecules are held together by rather weak non-classical inter-molecular C-H?O hydrogen bonds, resulting in dimeric units about inversion centers, forming eight- and ten-membered ring systems as R(2) (2)(8) and R(2) (2)(10) motifs.
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Cyclic arsenic-nitrogen cations.
Inorg Chem
PUBLISHED: 07-10-2009
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A series of different cyclo-diarsa-diazenium salts bearing several bulky groups such as supermesityl (Mes* = 2,4,6-tBu(3)C(6)H(2)) and m-terphenyl (2,6-Mes(2)-C(6)H(3), Mes = 2,4,6-Me(3)C(6)H(2)) and anions such as triflate (OTf = SO(3)CF(3) = trifluoromethylsulfonate) and tetrachloridogallate (GaCl(4)(-)) were synthesized and fully characterized. The novel 1-chloro-cyclo-1,3-diarsa-2,4-diazenium cation represents the first example of a binary cyclic As(III)/N four-membered heterocyclic cation, with a di- and tricoordinated As atom and a delocalized pi bond along the NAs((+))N unit. The addition of excess Me(3)SiN(3) yields the fully characterized cationic arsenic azide, 1-azido-cyclo-1,3-diarsa-2,4-diazenium-mu-azido-hexachlorido-digallate. The Cl(-)/N(3)(-) exchange is triggered by the action of the Lewis acid GaCl(3). Depending on the Me(3)SiN(3) stoichiometry, different mu-azido-hexachlorido-digallate salts with either 1-chloro- or 1-azido-cyclo-1,3-diarsa-2,4-diazenium cations or even a mixture of both are observed. Moreover, it was of special interest to study the distances between the cationic arsenic center and the anion in cyclo-diarsa-diazenium salts. A correlation between the color of the salt and the anion/cation distance, ranging between 2 and 8 A in cyclo-diarsa-diazenium salts of the type [R(2)N(2)As(2)Y](+)X(-) depending on the bulky group R (R = Mes*, Ter), the substituent Y (Y = Cl, N(3), OTf), and the anion X(-) (X = OTf, GaCl(4), Cl(3)Ga-N(3)-GaCl(3)), was established.
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Synthesis, structure, and bonding of weakly coordinating anions based on CN adducts.
J. Am. Chem. Soc.
PUBLISHED: 05-28-2009
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The addition of alkali or silver salts of dicyanoamide (dca), tricyanomethanide (tcm) and tetracyanoborate (tcb) to a solution of B(C(6)F(5))(3) in diethyl ether affords salts containing very voluminous B(C(6)F(5))(3) adduct anions of the type [E(CN)(n)(-)] x [B(C(6)F(5))(3)](n): E = N (dca_nb with n = 1, 2; b = B(C(6)F(5))(3)); E = C (tcm_nb with n = 1, 2, 3), and E = B (tcb_nb with n = 1, 2, 3, 4). Salts bearing these anions such as B[(CN) x B(C(6)F(5))(3)](4)(-) (= [B(CN)(4)(-)] x [B(C(6)F(5))(3)](4)), C[(CN) x B(C(6)F(5))(3)](3)(-) (= [C(CN)(3)(-)] x [B(C(6)F(5))(3)](3)), and N[(CN) x B(C(6)F(5))(3)](2)(-) (=[N(CN)(2)(-)] x [B(C(6)F(5))(3)](2)) can be prepared in good yields. They are thermally stable up to over 200 degrees C and dissolve in polar organic solvents. Depending on the stoichiometry mono-, di-, tri-, or tetraadduct formation is observed. The solid state structures of dca_2b, tcm_3b and tcb_4b salts show only long cation...anion contacts and thereby weak interactions, large anion volumes and only small distortions of the dca, tcm or tcb core enwrapped between B(C(6)F(5))(3) groups. That is why these anions can be regarded as weakly coordinating anions. On the basis of B3LYP/6-31+G(d) computations the energetics, structural trends and charge transfer of the adduct anion formation were studied. Since tcm_3b and tcb_4b are easily accessible and can also be prepared in large quantities, these anions may be utilized as a true alternative to other widely used weakly coordinating anions. Moreover, for both steric and electronic reasons it seems reasonable to expect that as counterions for cationic early transition metal catalysts such anions may show reduced ion pairing and hence increased catalytic activity.
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Reactions of 3-acylchromones with dimethyl 1,3-acetonedicarboxylate and 1,3-diphenylacetone: one-pot synthesis of functionalized 2-hydroxybenzophenones, 6H-benzo[c]chromenes and benzo[c]coumarins.
Org. Biomol. Chem.
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Reactions of 3-methoxalyl-, 3-polyfluoroacyl- and 3-aroylchromones with dimethyl 1,3-acetonedicarboxylate and 1,3-diphenylacetone in the presence of DBU proceed at the C-2 atom of the chromone system with pyrone ring-opening and subsequent formal [3 + 3] cyclocondensation to functionalized 2-hydroxybenzophenones, 6H-benzo[c]chromenes and benzo[c]coumarins, depending on the substituent at the 3-position. An NMR study and X-ray crystallographic analysis are reported. The compounds synthesized can be considered as promising scaffolds for the design of the novel UV-A/B and UV-B filters.
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Efficient synthesis of thieno[3,2-b:4,5-b]diindoles and benzothieno[3,2-b]indoles by Pd-catalyzed site-selective C-C and C-N coupling reactions.
Org. Biomol. Chem.
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Heteroacenes (thieno[3,2-b:4,5-b]diindoles and benzothieno[3,2-b]indoles) were efficiently synthesized from tetrabromothiophene and 2,3-dibromobenzothiophene in two steps, respectively. In the first step, a site-selective Pd-catalyzed C-C coupling is carried out, followed by a two-fold C-N coupling with aromatic and aliphatic amines.
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Catalytic trimerization of bis-silylated diazomethane.
J. Am. Chem. Soc.
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(Me(3)Si)(2)CNN isomerizes upon addition of traces of [Me(3)Si](+) ions to give (Me(3)Si)(2)NNC, which then undergoes an unusual trimerization reaction to give exclusively 4-diazenyl-3-hydrazinylpyrazole. As catalyst the isonitrilium ion, [(Me(3)Si)(2)NNC(SiMe(3))](+), was identified and fully characterized. Experiments and computations indicate a three-step reaction including isomerization of diazomethane, a C-C or N-C coupling, and a formal cycloaddition reaction. The kinetics and thermodynamics are discussed on the basis of DFT calculations.
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Reactions of titanocene bis(trimethylsilyl)acetylene complexes with carbodiimides: an experimental and theoretical study of complexation versus C-N bond activation.
J. Am. Chem. Soc.
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The reaction of the low valent metallocene(II) sources Cp(2)Ti(?(2)-Me(3)SiC(2)SiMe(3)) (Cp = ?(5)-cyclopentadienyl, 1a or ?(5)-pentamethylcyclopentadienyl, 1b) with different carbodiimide substrates RN?C?NR 2-R-R (R = t-Bu; R = Et; R = R = i-Pr; t-Bu; SiMe(3); 2,4,6-Me-C(6)H(2) and 2,6-i-Pr-C(6)H(3)) was investigated to explore the frontiers of ring strained, unusual four-membered heterometallacycles 5-R. The product complexes show dismantlement, isomerization, or C-C coupling of the applied carbodiimide substrates, respectively, to form unusual mono-, di-, and tetranuclear titanium(III) complexes. A detailed theoretical study revealed that the formation of the unusual complexes can be attributed to the biradicaloid nature of the unusual four-membered heterometallacycles 5-R, which presents an intriguing situation of M-C bonding. The combined experimental and theoretical study highlights the delicate interplay of electronic and steric effects in the stabilization of strained four-membered heterometallacycles, accounting for the isolation of the obtained complexes.
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Chlorine/methyl exchange reactions in silylated aminostibanes: a new route to stibinostibonium cations.
Inorg Chem
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The Lewis acid assisted triflate/methyl, azide/methyl, and chlorine/methyl exchange reactions between silicon and antimony have been studied in the reaction of R(Me(3)Si)N-SbCl(2) (R = Ter) with AgOTf, AgN(3), KOtBu, GaCl(3), and Me(3)SiN(3)/GaCl(3), resulting in the formation of different methylantimony compounds. Furthermore, R(Me(3)Si)N-SbCl(2) (R = SiMe(3)) was reacted with GaCl(3) at low temperatures to yield a hitherto unreported amino(chloro)stibenium cation, the proposed intermediate in methyl exchange reactions. Tetrachloridogallate salts bearing different stibinostibonium cations such as [(Me(3)Sb)SbMe(2)](+) and [(Me(3)Sb)(2)SbMe](2+) along with the GaCl(3) adduct of SbMe(3) were isolated from such R(Me(3)Si)N-SbCl(2)/GaCl(3) mixtures (R = SiMe(3)) at ambient temperatures, depending on the reaction parameters.
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One-Pot, Three-Component Synthesis of 7-Azaindole Derivatives from N-Substituted 2-Amino-4-cyanopyrroles, Various Aldehydes, and Active Methylene Compounds.
ACS Comb Sci
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An efficient and practical route to 7-azaindole framework has been developed by one-pot, three-component cyclocondensation of N-substituted 2-amino-4-cyanopyrroles, various aldehydes, and active methylene compounds in ethanol or acetic acid at reflux. Reactions involving tetronic acid, indane-1,3-dione, dimedone, and 5-phenylcyclohexane-1,3-dione gave carbocyclic fused 7-azaindoles, whereas Meldrums acid, benzoylacetonitrile, and malononitrile resulted in the highly substituted 7-azaindole derivatives, making this strategy very useful in diversity-oriented synthesis (DOS).
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A novel anticancer diterpenoid from Jatropha gossypifolia.
Nat Prod Commun
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Jatropha gossypifolia root bark is used in ethnomedicine for bacterial infections and cancer of the lungs. Phytochemical investigation resulted in the isolation and characterization of a potent anticancer and novel lathyrane diterpenoid compound, abiodone, with an unusual methylene group. The structure of this novel compound was established by 1D, and 2D NMR spectroscopic experiments a nd confirmed by X-ray analysis.
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Efficient [5 + 1]-strategy for the assembly of 1,8-naphthyridin-4(1H)-ones by domino amination/conjugate addition reactions of 1-(2-chloropyridin-3-yl)prop-2-yn-1-ones with amines.
Org. Biomol. Chem.
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A facile synthetic approach for the synthesis of 1,8-naphthyridine-4(1H)-one derivatives via a catalyst free and Pd-supported tandem amination sequence is developed and described. In a case of aliphatic amines reaction proceeds in a catalyst free mode, however anilines demand Pd-supported reaction conditions.
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Binary pnictogen azides--an experimental and theoretical study: [As(N3)4]-, [Sb(N3)4]-, and [Bi(N3)5(dmso)]2-.
Chemistry
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[PPh(4)][EI(4)] (E=As, Sb, Bi) salts were reacted with four and five equivalents of AgN(3) to form tetraazidopnictates and pentaazidopnictates of the type [PPh(4)][E(N(3))(4)] and [PPh(4)](2)[E(N(3))(5)], respectively. The synthesis of [PPh(4)][P(N(3))(4)] was also attempted from the reaction of P(N(3))(3) with [PPh(4)]N(3), but it yielded only the starting materials. Herein, we report the synthesis and structure elucidation of [PPh(4)][E(N(3))](4) (E=As, Sb) and pentaazidobismuthate, stabilized as the dimethyl sulfoxide (DMSO) anion adduct, [PPh(4)](2)[Bi(N(3))(5)(dmso)]. Successive anion formation along the series E(N(3))(3)+nN(3)(-) (n=1-3) and E(N(3))(5)+N(3)(-) was studied by density functional theory.
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