Microwave-Assisted Suzuki–Miyaura and Sonogashira Coupling of 4-Chloro-2-(trifluoromethyl)pyrido[1,2-e]purine Derivatives

The convenient preparation of three imidazo[1,2-a]pyridine-2-carboxamide intermediates is reported through known Strecker-Ugi type multicomponent reactions, Tschitschibabin type condensations, and further synthetic sequences. The derivatives were then efficiently converted to novel 4-chloro-2-(trifluoromethyl)pyrido[1,2-e]purines by their original reactions with 2,2,2-trifluoroacetamide, followed by subsequent dehydroxychlorination reactions. These compounds were cross-coupled under microwave irradiation through SuzukiMiyaura and Sonogashira palladium(0) catalysis to various aromatic and alkynyl reagents, thus providing the related C-4 substituted pyrido[1,2-e]purines of biological interest in good yields.