Synthesis of Difluoromethyl Ketones from Weinreb Amides, and Tandem Addition/Cyclization of <i>o</i>‐Alkynylaryl Weinreb Amides

Abstract

[Difluoro(phenylsulfanyl)methyl]trimethylsilane (PhSCF 2 SiMe 3 ) underwent a fluoride‐induced nucleophilic addition to the carbonyl group of Weinreb amides to provide the corresponding difluoro(phenylsulfanyl)methyl ketones. These were converted into difluoromethyl ketones through selective reductive cleavage of the phenylsulfanyl group. The reaction of o ‐alkynyl Weinreb amides derived from benzoic acid derivatives resulted in the formation of cyclized products through a 5‐ exo ‐ dig cyclization.