Construction of New Heterocyclic System, Imidazo[4,5-d]thiazolo[4,3-b]oxazole, via Cascade Reaction of Thioglycolurils with α-Bromoketones

A method for the synthesis of new heterocyclic system representatives, i. e. imidazo[4,5-d]thiazolo[4,3-b]oxazole derivatives, by the reaction of thioglycolurils with α-bromoketones has been developed. The reaction includes a cascade one-pot S-alkylation/nucleophilic addition/ring-opening/ring-closing process. This protocol is compatible with a broad scope of α-bromoketones, diastereoselectively affording diverse products with 3aS*,4aR*,8aR*-imidazo[4,5-d]thiazolo[4,3-b]oxazole core in 40–76 % yields.