Novel Annelations of Xanthines by the Reaction of 8-Aminoxanthines with Dimethyl Acetylene-dicarboxylate

Abstract

Annelations of xanthines by the reaction of dimethyl acetylenedicarboxylate (DMAD) with 7-alkyl-8-amino-1, 3-dimethylxanthines (3) have been investigated. Treatment of 3 with DMAD in refluxing methanol gave 5-alkyl-1, 3-dimethyl-9-methoxycarbonyl-1, 2, 3, 4-tetrahydro-5H, 7H-pyrimido[1, 2-e]purine-2, 4, 7-triones (4) and 7-alkyl-1, 2, 3, 6-tetrahydro-1, 3-dimethyl-8-(1, 2, 4, 5, 6, 7-hexamethoxycarbonyl-3-azatricyclo[2.2.1.0^{2, 6}]heptyl)purine-2, 6-diones (10). However, when the reaction was run in N, N-dimethylformamide, 5-alkyl-1, 3-dimethyl-1, 2, 3, 4-tetrahydro-7, 8, 11-tris(methoxycarbonyl)-5H, 9H[1, 3]-diazocino[1, 2-e]purine-2, 4, 9-triones (11), 5-alkyl-1, 3-dimethyl-7, 8-bis(methoxy-carbonyl)-1, 2, 3, 4, 9, 10-hexahydro-10-(methoxycarbonyl)methylene-5H[1, 3]-diazepino[1, 2-e]purine-2, 4, 9-triones (12), and 5-alkyl-1, 3-dimethyl-1, 2, 3, 4, 9, 10-hexahydro-7, 8, 9, 10-tetrakis(methoxycarbonyl)-5H[1, 3]-diazepino[1, 2-e]purine-2, 4-diones (13) were formed.