N-Boc-aminals as easily accessible precursors for less accessible N-Boc-imines: facile synthesis of optically active propargylamine derivatives using Mannich-type reactions

We developed a facile and practical synthesis of N-Boc-aminals, which can be used as precursors for less accessible N-Boc-imines. Aminals were obtained via simple dehydration condensation reactions of t-butyl carbamate (BocNH(2)) and various aldehydes in acetic anhydride, followed by filtration and washing with hexane. The obtained N-Boc-alkynylaminals could be successfully applied in enantioselective Mannichtype reactions, catalyzed by chiral phosphoric acids, to afford optically active propargylamine derivatives. (C) 2016 Published by Elsevier Ltd.