Bronsted acid catalyzed regioselective aza-Ferrier reaction: a novel synthetic method for alpha-(N-Boc-2-pyrrolidinyl) aldehydes

The 1,4-elimination reaction of (Z)-N-Boc-2-(4-methoxy-2-alkenyloxy)pyrrolidines (1) is shown to proceed with high (1E, 3E)-stereoselectivity to afford N-Boc-2-(1,3-dienyloxy)pyrrolidines (2); the Bronsted acid catalyzed aza-Ferrier reaction of the N-Boc-2-(1,3-dienyloxy) pyrrolidines (2) provides alpha-(N-Boc-2- pyrrolidinyl) aldehydes (3) in excellent yields with high alpha-regioselectivities.