The reactions of ethyl 3,4-dihydro-4-quinazolylacetate and its derivatives with cyclopentanone. An attempt at the synthesis of the 6,8-diazasteroid system VII

The reaction of ethyl 3,4-dihydro-4-quinazolylacetate ( 1a ) with cyclopentanone in the presence of trifluoroacetic acid gave mainly two decomposition products, carbostyril (VIII) and ethyl 2-aminocinnamate (IX). Two compounds which are suggested to have the 6,8-diazasteroid skeleton were also obtained in poor yield. Ethyl 3,4-dihydro-2-p-methoxyphenyl-4-quinazolylacetate (1b), however, gave 2-p-methoxyphenylquinazoline (XII) as a decomposition product and did not condense with cyclopentanone. Furthermore, two ethyl 3,4-dihydroquinazolylacetates substituted at the 2-position with cyclohexyl (1c) and methyl (1d) groups could not be converted to the expected diazasteroid system.