DABCO-Catalysed [3+2] Cyclization/Deformylation Cascade of p-Quinols with 3-Formylchromones: Access to Benzopyrone-Fused Tetracyclic Ring Systems

The construction of benzopyrone-fused hydrobenzofuranones via DABCO-catalyzed [3+2] cyclization/deformylation cascade of p-quinols with 3-formylchromones is described. The reaction works under mild reaction conditions to provide the desired products in 53-90% yields with complete diastereoselectivities. In addition, an enantioselective version with 81% ee is also realized in the presence of Takemoto's chiral thiourea catalyst.