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