Alkynone Annulation
Alkynone Annulation - Related Videos
01:27
Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation
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2023
Robinson annulation is a base-catalyzed reaction for the synthesis of 2-cyclohexenone derivatives from 1,3-dicarbonyl donors (such as cyclic diketones, β-ketoesters, or β-diketones) and α,β-unsaturated carbonyl acceptors. Named after Sir Robert Robinson, who discovered it, this reaction yields a six-membered ring with three new C–C bonds (two σ bonds and one π bond). The ring-forming reaction occurs in two stages: Michael addition and the subsequent intramolecular aldol condensation. The...
![Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F60786.jpg%3Fv%3D2026-09-01%252015%253A47%253A42&w=750&q=75)
07:12
Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
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2020
New routes for the synthesis of nitrogen-containing heterocycles utilizing cercosporin as a metal-free photocatalyst were developed.
07:30
A Direct, Regioselective and Atom-Economical Synthesis of 3-Aroyl-N-hydroxy-5-nitroindoles by Cycloaddition of 4-Nitronitrosobenzene with Alkynones
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Cited by 7 •
2020
3-Aroyl-N-hydroxy-5-nitroindoles were synthesized by cycloaddition of 4-nitronitrosobenzene with a conjugated terminal alkynone in a one-step thermal procedure. Preparation of the nitrosoarene and of the alkynones were adequately reported and respectively through oxidation procedures on the corresponding aniline and on the alkynol.
FAQs
Alkynone annulation generally proceeds through activation of one reactive site, followed by nucleophilic addition and intramolecular cyclization. Activation can increase the susceptibility of the alkyne or carbonyl to reaction, while the tethered arrangement allows the newly formed bond to close a ring. This sequence is important because several structural changes occur without requiring separate, isolated transformations.
Regioselectivity depends on how substituents, catalysts, and reaction conditions direct the sequence. Regioselectivity describes which atoms become connected and therefore which arrangement appears in the cyclic product. Changing these variables can favor one product structure over another, so they are not merely operational details; they determine the connectivity and structural diversity available from a given alkynone.
Activation of the alkyne and activation of the carbonyl offer different entry points into the same overall ring-forming sequence. In either case, the activated site supports nucleophilic addition, after which intramolecular cyclization builds the cyclic framework. Comparing these pathways helps explain why catalyst choice and reaction conditions can change the preferred product structure.
The identity of the atoms incorporated into the newly formed ring is a major structural outcome. Depending on the reaction design, alkynone annulation can provide oxygen-, nitrogen-, or carbon-containing rings. This flexibility lets chemists use the strategy beyond one narrow ring class, selecting conditions and substrates that support the cyclic framework needed for a target molecule or intermediate.
A practical conceptual workflow starts with an alkynone bearing the alkyne and ketone in a relationship that permits ring closure. The reaction then uses an appropriate activation mode, allows nucleophilic addition, and promotes intramolecular cyclization. Catalyst, substituent, and condition choices are evaluated together because each can influence regioselectivity and the structure of the cyclic product.
Chemists apply alkynone annulation when they need efficient access to cyclic structures, especially oxygen-, nitrogen-, or carbon-containing rings. The strategy is relevant to heterocycle synthesis and medicinal chemistry, where structurally varied ring systems are valuable. It also helps prepare complex intermediates while potentially reducing the number of synthetic steps required to reach them.