FLP Mediated Conversion of Difluorobenzylalkynes to Fluoroallenyl Oniums via an S N 1’ Pathway

Fluoroallenes represent an attractive class of synthons and are congeners to naturally occurring haloallenes, yet their preparation remains challenging. We report that frustrated Lewis pair (FLP) mediated selective monodefluorination of difluorobenzylalkynes generates geminal fluorobenzylalkyne onium salts as kinetic products, which subsequently isomerize into thermodynamically preferred fluoroallenyl onium salts through an S N 1′pathway. The onium‐stabilized fluoroallenes can undergo further derivatization at both allenic and onium positions, providing modular access to new fluorocarbon architectures.