Chemoselectivity Switching in the Rhodium‐Catalyzed Reactions of 4‐Substituted‐1‐sulfonyl‐1,2,3‐triazoles with Allenols: Noticeable Differences between 4‐Acyl‐ and 4‐Aryl‐Triazoles

Abstract

Tunable chemoselectivity (O-versus Cattack) in the rhodium-catalyzed reactions of allenols with 4-substituted-1-sulfonyl-1,2,3-triazoles has been achieved through the replacement of the 4-aryl substituent by a 4-acetyl moiety.

Rh-Catalyzed Aziridine Ring Expansions to Dehydropiperazines

“…This step forms ylide INT1 , which evolves into the metal-free ylide INT2 by the dissociation of the Rh 2 catalyst (Δ G R = −1.8 kcal/mol). A similar barrierless Rh 2 dissociation was found by us in the processes involving related aziridines , and by others in the fates of related transition metal ylides . Intermediate INT2 may undergo a cheletropic extrusion similar to that observed initially by Watanabe (see Scheme A) to produce the alkene intermediate INT3 .…”

Mechanistic Understanding of the Pd(0)-Catalyzed Coupling Cyclization of 1,2-Allenyl Ketones with Aryl Halides: A Computational Study

“…Nevertheless, the development of new approaches for the formation of transition-metal carbenes from nondiazo compounds has attracted substantial research interests . In this context, nondiazo carbene precursors, such as hydrazones, cyclopropenes, allenyl ketones, 1,2,3-triazoles, and others, have been demonstrated to be capable of generating transition-metal carbenoids in the presence of appropriate catalysts. Nevertheless, potentially alternative mechanisms via noncarbene pathways should not be overlooked in reactions involving nondiazo carbene precursors.…”

Deciphering the Chameleonic Chemistry of Allenols: Breaking the Taboo of a Onetime Esoteric Functionality

“…Reaction of allenols 356 with 4-aryl-substituted triazoles 374a yielded pirrolines 373 , 271 while 4-acetyl-substituted triazoles 374b provided diketones 375 , under otherwise identical reaction conditions ( Scheme 65 , top). 272 Thus, when 1-tosyl-1,2,3-triazoles 374a presented an aryl group in C4, allenols 356 behaved as C -nucleophiles, generating intermediates 378 as the product of the nucleophilic addition of the central allenic carbon onto the rhodium carbenoid in intermediates 377 . Further aza-cyclization of 378 yielded the experimentally observed pirrolines 373 ( Scheme 65 , bottom, left).…”

“…Alcaide and Almendros research group have envisioned a change on the selectivity of the nucleophilic attack of allenols to rhodium carbenoids derived from triazoles, depending on the heterocycle substitution. Reaction of allenols 356 with 4-aryl-substituted triazoles 374a yielded pirrolines 373 , while 4-acetyl-substituted triazoles 374b provided diketones 375 , under otherwise identical reaction conditions (Scheme , top) . Thus, when 1-tosyl-1,2,3-triazoles 374a presented an aryl group in C4, allenols 356 behaved as C -nucleophiles, generating intermediates 378 as the product of the nucleophilic addition of the central allenic carbon onto the rhodium carbenoid in intermediates 377 .…”