Microwave-assisted Intramolecular Dehydrogenative Diels-Alder Reactions for the Synthesis of Functionalized Naphthalenes/Solvatochromic Dyes

The overall goal of the following experiment is to generate functionalized napoles via a microwave assisted dehydrogenate dehydro ideals alder or DDDA reaction. This is achieved by microwave irradiation of styre precursors to produce diverse lene substrates. As a second step, a buckwald hardwig palladium catalyzed cross coupling reaction of the hynes with an amine is conducted.

This results in naphthalene containing electron donating and electron withdrawing groups that function as slv chromic fluorescent dyes, and are structurally related to a commercially available dye pro. Dan next solutions of the dye are prepared in order to measure the selected photo physical properties of the new substrates. This novel synthetic approach affords access to molecular architectures, possessing desirable photo, physical properties, and attractive chemical properties.

Results are obtained that show the intriguing SLV chromic behavior and large stoke shifts of these dyes based on fluorescence emission spectroscopy in a variety of solvents. The synthetic utility of the DDDA reaction is demonstrated by the synthesis of a number of nataline containing flora fours possessing tunable photo, physical and chemical properties. The main advantage of this technique over the existing methods, such as conventional eating, is that microwave assisted formation of desired products is achieved in shorter reaction times, higher yields, and mild reaction conditions.

In the case of DDS, other reaction microwave irradiation leads to the formation of more pure products because of increased product selectivity. This Method can help address key questions in the synthesis and development of aromatic substrates. In particular, functionalized nap fleeing compounds are valuable building blocks that can function as organic semiconductors and electronic devices, which include organic light emitting diodes.

They unique electronic properties make these small molecules ideal for application to liquid crystalline displays. Moreover, functionalized NAPLANs are prevalent in a number of biologically relevant natural products and pharmaceuticals. They play an integral part in asymmetric catalysis, and they also form the key C chromophore subunit of many popular synthetic dyes.

To begin the microwave assisted dehydrogenate DA reaction, prepare a 0.060 molar para chloro styrene derivative solution as described in the text protocol. This concentration is used because higher concentrations lead to the formation of undesired products. After placing the capped solution into the microwave synthesizer cavity irradiate the solution at 180 degrees Celsius for 200 minutes.

With stirring and with the fixed hold time on the pressure and temperature are monitored on the LED screen of the microwave. When the reaction vial is removed from the microwave, the solution is golden in color. Longer reaction times are not detrimental to the yield of the reaction.

Confirm the reaction is complete by thin layer chromatography abbreviated TLC employing 5%ethyl acetate hexane. As the eent visualize the TLC plate with UV light and potassium per magnate stain. Transfer the reaction to a simulation vial using one milliliter of one two di chloro Ethan to rinse the microwave reaction vial.

This results in approximately three milliliters of solution in the sation vial. Concentrate the contents of the sation vial under reduced pressure at 40 degrees Celsius. Using a rotary evaporator, evaporation of the solvent will require five to 10 minutes and 45 milligrams of AC crude brown oil will be obtained.

Purify the crude oil and confirm its identity by proton nuclear magnetic resonance spectroscopy. Begin the cross coupling reaction with addition of three milligrams of Ru phos pato cycle to an oven dried 0.5 to two milliliter bioTE microwave I radiation vial, equipped with a stir bar and cap the vial. Pierce the septum of the cap with a small gauge needle using a nitrogen tank connected to a manifold with an oil bubbler to control the nitrogen flow, connect the manifold to the needle, evacuate and refill the vial with nitrogen gas three times.

Once purging of the vial is complete, remove the needle. The microwave irradiation vial will act as a sealed tube during the reaction and the best results are obtained. When minimal air is present in the reaction vessel through the septum, a lithium bis trimethyl syl amid via syringe with stirring the solution will turn red.

After stirring for two to 10 minutes, add chloro naphthalene in 0.3 milliliters anhydrous tetrahedran via syringe. Additional THF can be used to fully dissolve the naphthalene. Following two to 10 minutes of stirring, add dimethyl amine as a solution via syringe and lower the reaction vessel into a preheated 85 degrees Celsius oil bath.

Heat the reaction for three hours at 85 degrees Celsius or until the reaction is complete by TLC. The reaction will be dark brown in color. For TLC, utilize 20%ethyl acetate hexanes as the eent and visualize the resulting plate with UV light and potassium permanganate stain.

After cooling the reaction room temperature, remove the vial cap and quench the reaction with saturated aqueous ammonium chloride solution. Using a 60 milliliter separatory funnel, separate the aqueous layer from the organic layer. Extract the aqueous layer three times with 12 milliliters of ethyl acetate.

Combine the organic layers in the separatory funnel and wash once with 15 milliliters of brine. Dry the combined organic layers over sodium sulfate for 10 minutes, and then remove the sodium sulfate by gravity filtration. Using a rotary evaporator.

Concentrate the resulting solution under reduced pressure at 30 degrees Celsius for five to 10 minutes. To evaporate the solvent, purify the resulting crude brown oil product by silica gel column chromatography with a 1.5 centimeter chromatography column and 5%ethyl acetate hexanes as elu. The dye will be obtained as 27 milligrams of a yellow solid.

Confirm the identity of the product by proton NMR spectroscopy as described in the text protocol. Transfer one milligram of the dye into a clean, dry, 10 milliliter volumetric flask and dilute to volume with di chloro methane or DCM to obtain a 0.4 times 10 to the negative third molar stock solution of the dye transfer. 253 microliters of the stock solution to a second 10 milliliter volumetric flask and dilute to volume with DCM to prepare a one times 10 to the negative fifth molar solution of the dye.

This solution will be used to collect both UV vis data as described in the text protocol and fluorescence data as demonstrated in this video. To perform fluorescence emission spectroscopy, fill a quartz fluorimeter cell with the one times 10 to the negative fifth molar dye solution and place it into the spectral fluorimeter. Avoid skin contact with the optical surfaces of the cell.

Set the instrumental parameters including an excitation wavelength at 334 nanometers slit width of two acquisition rate of 0.1 nanometers per second, and acquisition range from 390 to 750 nanometers. A 390 nanometer cut on filter is needed to remove scattered light from the emission source. Collect the fluorescence emission spectrum of the sample.

The fluorescence emission maximum is observed at 510 nanometers. Use excel or origin software to plot and analyze the collected data. Microwave irradiation of styre derivatives at 180 degrees Celsius.

Results in complete cyclo Penta b naphthalene formation in as little as 30 minutes and in high to quantitative yields. No dihydro naline byproduct is observed and by proton NMR spectroscopy, the products appear pure without the need for additional purification after a radiation. Various changes to the naline framework are well tolerated, utilizing these thermal conditions, including variations to the tether and the substitution pattern of the naline ring, incorporation of an array of electron withdrawing groups, and also altering the location of the electron withdrawing group to create fused cyclopentane products.

The synthesis of fluoro fours follows a two step protocol of a microwave assisted dehydrogenate dehy DA reaction, followed by a palladium catalyzed cross coupling reaction. As a representative example, a para chloro substituted styrene is under the aforementioned conditions and then subjected to palladium catalyzed cross coupling conditions to produce the desired fluorescent dye. The photo physical properties of the die are studied in various solvents of differing polarity, which result in a color change due to solvent polarity.

In a process called solve aach, CHRO fluorescent emission spectroscopy reveals that the fluorescent dye exhibits remarkable solve themic behavior. This figure shows the fluorescent dye solubilized in toluene one four dioxin DCM and dimethyl sulf oxide and observed under longwave UV light fluorescent emission spectra of the new fluorescent dye. In Cyclohexane toluene one four dioxin, T-H-F-D-C-M chloroform.

Acetonitrile, DMSO and ethanol reveal a rohr shift from cyclo heine to ethanol as great as 112 nanometers. These results are also improved from those reported for a commonly used commercially available salvage chromic dye. Dye pro Dan, After its development, this technique will pave the way for researchers in the field of organic synthesis, prepare slv AHR dyes that can be applied to biosensing and imaging.

Future of molecular imaging depends on the design, synthesis, and development of new reporter molecules for living systems. However, access to fluorescent compounds with desired photo physical properties and sensitivity remains limited. Our ability to rationally design and tune the properties of these newly synthesized flora fours is made possible by the synthetic versatility of the Dehydrogenated d Aldo reaction.

After watching this video, you should have a good understanding of how to safely perform microwave assisted reactions to synthesize functionalize lings, which can transformed in one step to subatomic dyes from readily available sterile precursors.