E-Selective Radical Difunctionalization of Unactivated Alkynes: Preparation of Functionalized Allyl Alcohols from Aliphatic Alkynes

Radical difunctionalization of aliphatic alkynes provides direct access to valuable multi-substituted alkenes, but achieving a high level of chemo- and stereo-control remains a formidable challenge. Herein we report a novel photoredox neutral alkyne difunctionalization through functional group migration followed by radical-polar crossover and energy transfer-enabled stereoconvergent isomerization of alkenes. In this sequence, a hydroxyalkyl and an aryl group are incorporated concomitantly into an alkyne, leading to diversely functionalized E-allyl alcohols. The scope of alkynes is noteworthy, and the reaction tolerates aliphatic alkynes containing hydrogen donating C-H bonds which are prone to intramolecular hydrogen atom transfer. The protocol features broad functional group compatibility, high product diversity and exclusive chemo- and stereoselectivity, thus providing a practical strategy for the elusive radical difunctionalization of unactivated alkynes.