Engaging Yne‐Allenes in Cycloaddition Reactions: Recent Developments

Abstract

Comprehensive Summary Yne‐allenes bearing both a C—C triple bond and an allene unit are a class of focal substrates in organic synthesis, in view of their structure diversity, high reactivity and intermediate variety in the past years. Engaging yne‐allenes in numerous annulation cascades provides efficient and direct accesses to elaborate functionalized polycyclic molecular architectures in a convergent manner. There are lots of types of catalytic chemical reactions such as intramolecular cyclizations, cycloisomerizations, intermolecular annulations, and bicyclizations as well as tricyclizations with the assistance of Lewis acids, Brønsted acids, bases, transition metals, and other catalysts. This review provides an overview of the chemistry developed with transformations of yne‐allenes by discussing their general and specific reactivities, presenting and commenting on their mechanisms as well as their applications.

Visible-Light-Promoted Cyanoalkylation/Cyclization Cascade Reaction to Assemble Polyheterocycles in Continuous Flow

“…In this context, radical cascade reactions are one of the most straightforward and atom-economical transformations; they allow the synthesis of diversely substituted phenanthridines . A series of elegant studies established radical cascade reactions as a powerful method for creating such compounds . In 1995, Nanni and co-workers reported an inspiring breakthrough: they developed the first cascade reaction to access 6-substituted phenanthridines through a homolytic aromatic substitution .…”

Highlighting the Rich Chemistry of the Allenone Moiety

“…Besides, choosing the adequate substituent can also modulate the allene reactivity providing divergent transformations, especially when electron‐donating or electron‐withdrawing groups are attached to the allene system. Among the family of electronically tuned allenes, allenones, constituted by an allene moiety and a ketone, have appeared as recurring motifs in organic synthesis, natural products and mechanistic investigations, showing unique properties and synthetic applications [10–22] …”

“…Among the family of electronically tuned allenes, allenones, constituted by an allene moiety and a ketone, have appeared as recurring motifs in organic synthesis, natural products and mechanistic investiga-tions, showing unique properties and synthetic applications. [10][11][12][13][14][15][16][17][18][19][20][21][22] During the last two decades, the chemistry of allenones has resulted in an increasing number of contributions describing both their synthesis and applications. Regarding reactivity, these systems can operate as Michael acceptors in nucleophilic additions, cyclization counterparts in cycloaddition reactions, or five-membered ring precursors through cycloisomerizations.…”

Divergent Reactivity of Phosphorylated and Related Allenes: [4 + 2] Cycloaddition with 3,6-Diphenyltetrazine, Self-Addition Leading to Dimers and [Pd]-Complex Formation

“…Allenes (R 2 CCCR 2 ′) are versatile synthons compared to normal olefins and alkynes due to the presence of two cumulative CC double bonds and three reactive carbon centers. , They can readily undergo inter-/intramolecular cyclizations/cycloadditions to afford useful organic scaffolds . Allenes are also excellent partners for the [2 + 2] and [4 + 2] cycloadditions with alkenes/alkynes or self-dimerization leading to the cyclobutane/cyclobutene or cyclohexane/cyclohexene skeletons.…”