Reactions of 8, 9-Dihydroxanthines with Acetylenic Compounds. Formation of Heteropropellanes

Abstract

Reactions of 7-substituted 1, 3, 9-trimethyl-8, 9-dihydroxanthines (3) with dimethyl acetylenedicarboxylate afforded heteropropellanes (5) in good yields. The reactions with methyl propiolate afforded pyrimidodiazepines (7) as well as propellanes (6) when the xanthines have small substituents at the 7 position. The mechanisms of formation of the products are also discussed.