2,6-Disubstituted 5,6,7,8-tetrahydropyrido[4,3-d]pyrimidin-4(3H)-one (6-azaquinazoline) derivatives 7a-e were synthesized from N-substituted 3-methoxycarbonyl-4-piperidones 5a, b and amidines 6a-c. Compounds 7a-d and the debenzylated derivatives 8a-c underwent dehydrogenation in xylene or in nitrobenzene in the presence of a palladium-carbon catalyst furnishing products 9a, b and d or 10a-c, respectively. It was found that the formation of the two types of products, 9 or 10, from the same molecules depends on the substituents at positions 2 and 6, and on the inert or oxidative character of the solvent used. The quinonediimine forms 9a, b can be considered to be intermediates of the transformation 7a, b→10a, b.
|Number of pages||6|
|Journal||Journal of the Chemical Society, Perkin Transactions 1|
|Publication status||Published - Jan 1 1992|
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