Accessing Complex Tetrahydrofurobenzo-Pyran/Furan Scaffolds Lewis-Acid Catalyzed Bicyclization of Cyclopropane Carbaldehydes with Quinone Methides/Esters.

Herein, we report a straightforward one-pot synthesis of tetrahydrofurobenzopyran and tetrahydrofurobenzofuran systems an in situ ring-expansion of the cyclopropane carbaldehydes followed by a [2 + ] cycloaddition with the quinone derivatives. The transformation not only unveils a new reaction mode of cyclopropane carbaldehydes with quinone methides/esters, but also promotes a step-efficient diastereoselective route to the sophisticatedly fused oxygen tricycles that can be further dehydrogenated to access the valued dihydro-2-furo[2,3-]chromene frameworks.