Alkene Difunctionalization Triggered by a Stabilized Allenyl Radical: Concomitant Installation of Two Unsaturated C-C Bonds

Radical-mediated difunctionalization of alkenes provides a promising approach to introduce one alkenyl or alkynyl group to target compounds. However, simultaneous installation of two unsaturated C-C bonds via alkene difunctionalization remains elusive, attributable to the high instability and transient lifetimes of alkenyl and alkynyl radicals. Herein, we report the photocatalytic 1,2-alkynylalkenylation and 1,2-enynylalkenylation of alkenes for the first time, triggered by the intermolecular addition of a stabilized allenyl radical to an alkene. A portfolio of strategically designed, easily accessible dual-function reagents are applied to a radical docking-migration cascade. The protocol has broad substrate scope and efficiently increases the degree of unsaturation.

Automated summary

The radical-mediated difunctionalization of alkenes introduces one alkenyl or alkynyl group to target compounds, but simultaneous installation of two unsaturated C-C bonds via alkene difunctionalization remains challenging due to the high instability of alkenyl and alkynyl radicals. This study reports the successful photocatalytic 1,2-alkynylalkenylation and 1,2-enynylalkenylation of alkenes, utilizing stabilized allenyl radicals for intermolecular addition, with a broad substrate scope and increased degree of unsaturation.