A new regio- and chemoselective approach to beta-keto amides and beta-enamino carboxamides via 1,3,2-dioxaborinanes

摘要

Surprisingly, 5,6-disubstituted 2,2-difluoro-4-alkoxy-,3,2-dioxaborinanes, which can be easily obtained from beta-keto esters, reacted regio- and chemoselectively with amines under mild reaction conditions to form 2,2-difluoro-4-alkylamino-1,3,2-dioxaborinanes in almost quantitative yields. The latter compounds can be easily deprotected, yielding beta-keto amides, or directly transformed into beta-enamino carboxamides. This procedure was also applied to the reaction of 2,2-difluoro-4-alkoxy-1,3,2-dioxaborinanes with arylhydrazines which selectively afforded beta-hydrazono esters, in some cases without further cyclization to pyrazolones. [References: 28]