Brønsted acid-mediated selective α-alkenylation of 3,4-dihydro-2H-pyrans

A protocol for the synthesis of α-alkenylated tetrahydropyrans (THPs) with 3,4-dihydro-2 H -pyran derivatives and potassium alkenyltrifluoroborates was achieved in the presence of a Brønsted acid and a Lewis acid under mild reaction conditions.