Brønsted Acid-Mediated Stereoselective Cascade Construction of Functionalized Tetrahydropyrans from 2-(Arylmethylene)cyclopropylcarbinols and Aldehydes

(E)- and (Z)-2-(Arylmethylene)cyclopropylcarbinols 1 could be converted to the corresponding tetrahydropyrans 2 and 3 stereoselectively in the presence of Brønsted acids MsOH or TsOH under mild conditions. A plausible Prins-type reaction mechanism has been proposed.