Asymmetric synthesis of N-phenylethyl- 2-phenyldecahydroquinolin-4-ones via Lewis acid catalyzed imino-Diels±Alder reaction ReneÂe Paugam, a, * Emmanuelle Valenciennes, a Linda Le Coz-Bardol, a Jean-Christophe Garde, a Lya Wartski, a, * Monique Lance b and Martine Nierlich b a Laboratoire des Carbocycles, Unite  Associe Âe au CNRS 8615, Institut de Chimie Mole Âculaire d'Orsay, Universite  Paris-Sud, 91405 Orsay, France b C.E.A. Saclay, SCM 91191 Gif-sur-Yvette, France Received 19 April 2000; accepted 18 May 2000 Abstract The asymmetric synthesis of N-phenylethyl-2-phenyldecahydroquinolin-4-ones was performed via a Lewis acid catalyzed imino-Diels±Alder reaction between the enantiopure (R)-N-phenylethylbenzylideneimine and the trimethylsilyl enol ether of acetylcyclohexene. The regio- and stereoselective formation of inter- mediary bicyclic enoxysilanes, followed by their stereoselective protonation was evidenced. The initial stereoselectivity was kept only if the reaction mixture was treated using controlled basic conditions. Three enantiopure title compounds were isolated with a 5±15% yield. # 2000 Elsevier Science Ltd. All rights reserved. 1. Introduction Hetero Diels±Alder reactions with imino-dienophiles and activated dienes under Lewis acid catalysis have received increasing interest after the pioneer work of Danishefsky, since they play an important role in the synthesis of nitrogen heterocycles. 1 4 The asymmetric version has been investigated by dierent groups using either chiral imines 5 8 or chiral Lewis acids; 9,10 more recently, the chirality was introduced on both partners. 11 We have previously reported the reaction of trimethylsilyl enol ethers of acetylcyclopentene and acetylcyclohexene with various N-substituted imines in the presence of Lewis acids which provides an easy access to N-substituted octahydropyrindin-4- and decahydroquinolin-4-ones, respectively. 12 14 0957-4166/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S0957-4166(00)00201-9 Tetrahedron: Asymmetry 11 (2000) 2509±2523 * Corresponding authors. Fax: +33(1)69156278 (R.P.), +33(1)69086640 (L.W.); e-mail: rpaugam@icmo.u-psud.fr, lwartski@icmo.u-psud.fr, nierlich@drecam.cea.fr