Synthesis of 3-vinylpiperidines, 3-ethylidenepiperidines and 5-functionalized-1,2,3,4-tetrahydropyridines

Reaction of 1-azapentadienyl anions, generated by deprotonation of N-(2-buten-1-ylidene)alkylamines, with 1-bromo-3-chloropropane led to the formation of N-[2-(3-chloropropyl)-3-buten-1-ylidene]alkylamines. By reaction with nucleophiles and bases, the latter functionalized imines were converted into unsaturated piperidines, i.e. 3-vinylpiperidines, 3-ethylidenepiperidines, 5-vinyl-1,2,3,4-tetrahydropyridines and 5-(2-cyanoethyl)-1,2,3,4-tetrahydropyridines. 5-Vinyl-1,2,3,4-tetrahydropyridines proved to be suitable dienes in Diels-Alder reactions with N-phenylmaleimide, giving rise to octahydro-1H-pyrrolo[3,4h]quinoline-1,3-diones. (C) 1998 Elsevier Science Ltd. All rights reserved.