AcOH-Catalyzed Rearrangements of Benzo[e][1,4]diazepin-2(and 3)-ones: Easy Access to 1,4-Dihydroquinazolines and Their Condensed Analogues

Presented herein is a novel synthesis of new 2-(quinolin-4-yl)-1,4-dihydroquinazoline systems 8, in which the acid-catalyzed rearrangement of spiro­[benzo­[e]­[1,4]­diazepine-3,4′-quinolin]-2­(1H)-ones generated in situ from 3-(2-aminophenyl)-5H-benzo­[e]­[1,4]­diazepin-2­(1H)-ones 6 with acetone and alkylmethyl ketones has been realized as an important step. An attempt to synthesize isomeric 2-(2-aminophenyl)-5H-benzo­[e]­[1,4]­diazepin-3­(4H)-one 6′a by hydrolysis of the corresponding N-{2-[5H-benzo­[e]­[1,4]­diazepin-3­(4H)-on-2-yl]­phenyl}­acetamide 5′a led to a new heterocyclic system, 6-methyl-8,13-dihydro-13aH-quinazolino­[4,3-b]­quinazolin-5-ium 13a-carboxylate 14, as a result of an unexpected rearrangement. In addition, it is noteworthy that during the hydrolysis of N-{2-[5H-benzo­[e]­[1,4]­diazepin-2­(1H)-on-3-yl]­phenyl}­acetamides 5, the not previously described 14-dihydro-5H-14,5a-(epimino­[1,2]­benzo)­benzo­[5,6]­[1,4]­diazepin­[2,1-b]­quinazolin-6­(7H)-ones 7 were unexpectedly obtained.