[Chemical and pharmaceutical research on pyran derivatives. XI. Synthesis of 2-dialkylamino-4-oxo-10-methyl-4H-naphtho[2,3b]pyrans].

Reaction of N,N-dialkylethoxycarbonylacetamides with 1-methyl-2-naphthol, in the presence of phosphorus oxychloride, gave rise to the formation of 2-dialkylamino-4-oxo-10-methyl-4H-naphtho[2,3-b] pyrans through the preliminary attack of the amide-phosphorus oxychloride reactant at the phenolic hydroxyl and cyclization at position 3 of the naphthalene moiety. However when (N-alkyl,N-phenyl)ethoxycarbonylacetamides were used in the reaction an ortho position of the N-phenyl group was involved in the cyclization and 1-alkyl-2(1'-methyl-2'-naphthoxy)-4-quinolones were achieved. Pharmacological investigation showed that some naphtho[2,3-b]pyran derivatives have neurotropic activity of the sedative, anticonvulsant and antidepressant type very similar to that shown by previously studied 1-oxo-3-dialkylamino-1H-naphtho[2,1-b]pyrans (5).