Catalytic regio- and stereoselective intermolecular [5+2] cycloaddition via conjugative activation of oxidopyrylium.

A catalytic stereodivergent intermolecular [5+2] cycloaddition of maltol-type oxidopyrylium through conjugative activation was reported, which featured high stereoselectivity, good compatibility and mild conditions, providing a convenient access route to various seven-membered heterocycles in moderate to excellent yields. In addition, a discrete mechanism was proposed to illustrate the stereoselectivity.