[Chemistry and pharmacology of pyran derivatives. XVII. Synthesis of 2-(dialkylamino)-5-hydroxychromones and their transformation to derivatives of 2H-pyran[4,3,2-de]-1-benzopyran].

Reaction of resorcinol with N,N-dialkylethoxycarbonylacetamides in PhCl and in the presence of POCl3 gave rise to 2-(dialkylamino)-5-hydroxychromones (I; NR2 = NMe2, NEt2, pyrrolidinyl, or piperidinyl). Reaction of I with CH2(CN)2 in Ac2O gave [5-acetoxy-2-(dialkylamino)-4H-chromen-4-ylidene]malononitriles; treatment of the latter with HCl resulted in cyclization to 5-(dialkylamino)-2-imino-2H-pyrano[4,3,2-d,e]-1-benzopyrans (II). I, when treated with MeI, gave the corresponding 5-methoxychromones, which in turn yielded 4H-chromen-4-ylidene derivs. by reaction with CH2(CN)2 in Ac2O. The hydrolysis of the latter compds. with HCl resulted in the formation of 2-(dialkylamino)-4-methyl-5-methoxychromenilium salts. Four representatives of these different classes were tested for antiallergic properties in rats. 2-(Dimethylamino)-5-methoxychromone and II (NR2 = NEt2) had considerable activity but also high toxicity.