Imino-Diels-Alder reactions of 1-aryl-3-(trialkylsiloxy)-1,3-butadienes in solution and the solid phase

Imino-Diels-Alder reactions between 1-aryl- or 1-heteroaryl-3-(trialkylsiloxy)-1,3-butadienes and imines derived from ethyl glyoxylate have been studied. When an achiral imine was used, the diastereoselectivity depended on the nature of the aryl or heteroaryl system; diastereoselectivities > 90% were observed with methoxyphenyl or indolyl substituents, but were much lower for nitro substituents. High diastereoselectivities were also achieved if a chiral imine derived from methylbenzylamine was used as the dienophile. Solid-supported imine dienophiles yielded the N-deprotected cycloadducts by direct cleavage from the resin with no diastereoselectivity. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).