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 3a S *,4a R *,8a R *‐imidazo[4,5‐ d ]thiazolo[4,3‐ b ]oxazole core in 40–76 % yields.