Catalytic imino Diels-Alder reaction by triflic imide and its application to one-pot synthesis from three components

An imino Diels-Alder reaction of 2-siloxydienes with aldimines catalyzed by triflic imide (Tf2NH; 0.1 similar to 10 mol % amount) has been developed leading to substituted piperidin-4-ones. Tf2NH catalyst is compatible with basic functions, such as pyridine and indole rings in the imino Diels-Alder reaction. Furthermore, X-ray crystallographic analysis indicates that trans-2,6-diphenyl-4-piperidinone 4a obtained by this reaction has a unique conformation in the solid state. (c) 2006 Elsevier Ltd. All rights reserved.