Efficient synthesis of ortho-carborane by reaction of propiolic acid tert-butyl ester with decaborane(14)

Abstract

Reaction of propiolic acid tert-butyl ester I and decaborane(14) at 90 degreesC did not give the expected carborane carboxylic acid tert-butyl ester 3 but directly unsubstituted ortho-carborane 2 which was isolated in 52% yield as pure material, An in situ de-tert-butoxycarbonylation of the first formed carborane carboxylic acid tert-butyl ester 3 via a six membered transition state is suggested for this domino process.