Borane catalyzed transesterification of tert -butyl esters using α-aryl α-diazoesters.

The B(C 6 F 5 ) 3 -catalyzed transesterification of a series of 3-alkenyl-oxindoles and other unsaturated tert -butyl esters with aryl-diazo esters is reported. This protocol is facile and generally high yielding proceeding under mild conditions and is remarkably chemoselective leaving the CC bonds intact.