Diastereoselective Diels-Alder reactions of N-sulfonyl-1-aza-1,3-butadienes with optically active enol ethers: An asymmetric variant of the 1-azadiene Diels-Alder reaction

A detailed study of a room-temperature asymmetric Diels-Alder reaction of N-sulfonyl-1-aza-1,3-butadienes reports the series of 19 enol ethers bearing chiral auxiliaries with many providing highly diastereoselective reactions, largely the result of an exquisitely organized (4+2) cycloaddition transition site. Three readily accessible and unexplored auxiliaries rationally emerged from the studies and provide remarkable selectivities that promise to be useful in systems.