Stereoselective Synthesis of ( E )-α-Deuterated α,β-Unsaturated Carboxylic Acids via Silver-Promoted Defluorinative Deuteration of gem -Difluoroallenes

Deuterated unsaturated carboxylic acids represent a class of valuable motifs in medicinal chemistry; however, stereoselective deuteration at the vinylic position remains a significant challenge. Herein, we report an AgOTf-mediated, highly (E)-selective deuteration and defluorination of gem-difluoroallenes with D2O. This protocol features operational simplicity, a broad substrate scope, and excellent deuterium incorporation (up to 98%) with good E/Z selectivity (up to 17:1). Mechanistic studies reveal that D2O serves as both the deuterium and oxygen sources through an acyl fluoride intermediate.