Highly diastereoselective synthesis of 2-azabicyclo[2.2.1]hept-5-ene derivatives : bronsted acid catalized aza-diels-alder reaction between cyclopentadiene and imino-acetates with two chiral auxiliaries

Abstract

The cycloaddition between protonated glyoxylate imines possessing two chiral auxiliaries, N-(S)- or N-(R)-1-phenylethyl and (-)-8-phenylmenthyl or (+)-8- phenylneomenthyl, and cyclopentadiene is described. The absolute configuration of all adducts formed was unequivocally assigned through NMR, specific optical rotation and X-ray data of appropriated derivatives. Experimental results confirm the highly exoselectivity for these aza-Diels–Alder reactions, single adducts being obtained from combinations of (8PM)-(R-PEA) and (8PNM)-(S-PEA).