A highly diastereoselective series of Nicholas cyclisation reactions of N-Boc-protected propargylamines

The reaction of N-Boc-protected propargylamine with salicylaldehyde derivatives and their subsequent Nicholas cyclisation reaction to provide a range of novel benzopyrans is reported. The cyclisation reactions proceeded with excellent levels of diastereoselectivity to afford compounds with cis-relative stereochemistry. As far as we are able to ascertain these are the first reported examples of Nicholas cyclisation reactions of propargyl alcohols that bear a terminal alkynyl N-protected amino motif.