Ein neuer zugang zu indeno[1,2-b]pyridinen

A new synthesis of 5H-indeno[1,2-6]pyridines [IV] starting from 4-cyanobutyrophenones [I] or their cyclization products, the 6-phenyl-3,4-dihydropyridin-2-ones [II], is reported. The condensation of I or II in polyphosphoric acid with aromatic or heteroaromatic aldehydes [III] yields 1,2,3,4-tetrahydro-5H-indeno[1,2-b]pyridin-2-ones [IV]. 2,3,4,4a,5,9b-Hexahydro-1H-indeno[1,2-b]pyridines [X, XI] which were previously difficult to obtain can now be easily synthesized from compounds IV.