Iridium-Catalyzed Enantioselective and Chemodivergent Allenylic Alkylation of Vinyl Azides for the Synthesis of α-Allenylic Amides and Ketones

The first enantioselective synthesis of alpha-allenylic amides and ketones through allenylic alkylation of vinyl azides is reported. In these chemodivergent reactions, cooperatively catalyzed by a Ir-I/phosphoramidite, olefin) complex and Sc(OTf)(3), vinyl azides act as the surrogate for both amide enolates and ketone enolates. The desiccant (molecular sieves) plays a crucial role in controlling the chemodivergency of this enantioconvergent and regioselective reaction: Under otherwise identical reaction conditions, the presence of the desiccant led to alpha-allenylic amides, while its absence resulted in alpha-allenylic ketones. Utilizing racemic allenylic alcohols as the alkylating agent, the overall process represents a dynamic kinetic asymmetric transformation (DyKAT), where both the products are formed with the same absolute configuration. To the best of our knowledge, this is the first example of the use of vinyl azide as the ketone enolate surrogate in an enantioselective transformation.

Automated summary

The first enantioselective synthesis of alpha-allenylic amides and ketones through allenylic alkylation of vinyl azides is reported. The presence of a desiccant plays a crucial role in controlling the chemodivergency of this enantioconvergent and regioselective reaction. Utilizing racemic allenylic alcohols as the alkylating agent, the overall process represents a dynamic kinetic asymmetric transformation (DyKAT) where both the products are formed with the same absolute configuration.