Abstract
Both the reactions of 3, 4-dihydro-4-quinazolinylmethyl alkyl ketones (4) with active methylene compounds or ketones (NuH) without a catalyst and in the presence of alumina as a catalyst were carried out, and resulted in the transformation of 4 into quinolines (3). Thus 2-(3, 4-dihydro-4-quinazolinyl) acetophenone (4a), 2-(3, 4-dihydro-4-quinazolinyl)-cyclohexanone (4b), and 1-(3, 4-dihydro-4-quinazolinyl)-2-propanone (4c) reacted with diethyl malonate (NuH-2), phenylacetonitrile (NuH-3), acetophenone (NuH-4), cyclopentanone (NuH-5), and cyclohexanone (NuH-6) without catalyst to give 2-phenylquinoline (3b), 1, 2, 3, 4-tetrahydroacridine (3c), and 2-methylquinoline (3d), respectively, together with the dissociation product, quinazoline (1a), although the yield of 3 was very poor. Alumina as a catalyst accelerated these reactions to give 3 in moderate yield. Even the reaction with chloroform (NuH-7) and ethyl orthoformate (NuH-8) gave 3 in good yield. The phenyl and methyl groups substituted at the 2-position prevented 4 from transforming into 3 in both the reactions without a catalyst and in the presence of alumina. A similar transformation was also found between 4, 5-dihydro-5-hydroxy-1-methyl-1H-pyrazolo [3, 4-d] pyrimidine-4-malononitrile (5) and NuH in the presence of alumina, and resulted in the formation of 6-amino-1-methyl-1H-pyrazolo [3, 4-b] pyridine-5-carbonitrile (8). The possible mechanism of the reaction was discussed.
