Tetrahydrocyclopenta[e]pyrido[3,2-b][1,4]diazepine and -cyclopenta[e]pyrido[2,3-b][1,4]diazepine derivatives

In pursuing the study on compounds obtained by condensation of N-monoalkylated aromatic and hetero-aromatic diamines with α- and β-ketoesters, 7,8,9,10-tetrahydrocyclopenta[e]pyrido[3,2-b][1,4]diazepin-6(5H)-ones 4a, 4b and 5,7,8,10-tetrahydrocyclopenta[e]pyrido[2,3,-b][l,4]diazepin-9H)-ones 5a, 5b were prepared starting from 2,3-diaminopyridine or 2,3-diamino-5-chloropyridine and ethyl 2-oxo-cyclopentanecarboxylate. Compounds 4a,b and 5a,b suffer thermally induced ring contraction to the imidazolone derivatives 8a,b and 7a,b respectively and are unsuitable for preparing diazepinone derivatives. Thus the methylated diazepinones 15, 17 and 18 , stable on heating, were prepared. Compound 17 was transformed into the clozapine analogue 22 , through the diazepinthione 20 and its S-methyl derivative 21 .