Oxidative C H alkynylation of 3,6-dihydro-2H-pyrans

Abstract Current synthesis of α-substituted 3,6-dihydro-2 H -pyrans dominantly relies on functional group transformation. Herein, a direct and practical oxidative C H alkynylation and alkenylation of 3,6-dihydro-2 H -pyran skeletons with a range of potassium trifluoroborates is developed. The metal-free process is well tolerated with a wide variety of 3,6-dihydro-2 H -pyrans, rapidly providing a library of 2,4-disubstituted 3,6-dihydro-2 H -pyrans with diverse patterns of α-functionalities for further diversification and bioactive small molecule identification.