Convergent Synthesis of 1,4-DicarbonylZ-Alkenes through Three-Component Coupling of Alkynes,α-Diazo Sulfonium Triflate, and Water

We report a general protocol for the convergent synthesis of 1,4-dicarbonylZ-alkenes form alkynes using alpha-diazosulfonium triflate and water. The C & xe0c8;O, C & xe0c8;C, and C-H bonds are formed under mild conditions with a wide range of functionalgroups tolerated. The reaction exhibits excellentZ-selectivity and complete regioselectivity. The resulting 1,4-dicarbonylZ-alkenescan smoothly undergo follow-up conversion to a variety of heteroaromatic scaffolds. Moreover, the reaction also provides a facileaccess to the corresponding deuteratedZ-alkenes and deuterated heteroarenes with a high level of deuterium incorporation (90-97% D-inc.) by directly using D2O, thus rendering the method highly valuable. The comprehensive mechanistic studies indicate thata free carbyne radical intermediate is formed via the photocatalytic single electron transfer process, and KH2PO4plays a crucial rolein significant improvements on yield and selectivity based on density-functional theory calculations, providing a new direction forradical coupling reactions of diazo compounds.

Automated summary

A general protocol for the synthesis of 1,4-dicarbonyl Z-alkenes from alkynes using alpha-diazosulfonium triflate and water has been reported, showing excellent Z-selectivity and complete regioselectivity. The resulting compounds can be smoothly converted to various heteroaromatic scaffolds. Mechanistic studies suggest the formation of a free carbyne radical intermediate and the crucial role of KH2PO4 in enhancing yield and selectivity, providing a new direction for radical coupling reactions of diazo compounds.