Unexpected behavior of enaminones: interesting new routes to 1,6-naphthyridines, 2-oxopyrrolidines and pyrano[4,3,2-de][1,6]naphthyridines.

Reaction of enaminones 1a-d with 2-aminoprop-1-ene-1,1,3-tricarbonitrile (2) in the presence of AcOH/NH₄OAc afforded 7-amino-5-oxo-5,6-dihydro-1,6-naphthyridine-8-carbonitrile derivatives 9a-d. On the other hand, 2-aminopyrano[4,3,2-de] [1,6]naphthyridine-3-carbonitriles 20a-c,e were the only obtained products from the reactions of 1a-d with 2 in the presence of AcOH/NaOAc, while 1d afforded [3,5-bis-(4-chloro-benzoyl)-phenyl]-(4-chloro-phenyl)-methanone 21 under the same condition. The reaction of 2 with diethyl acetylenedicarboxylate in the presence of AcOH/NH₄OAc afforded (4-cyano-5-dicyanomethylene-2-oxo-2,5-dihydro-1H-pyrrol-3-yl)-acetic acid ethyl ester 15B.