Highly Stereoselective Synthesis of Fused Tetrahydropyrans via Lewis-Acid-Promoted Double C(sp3)-H Bond Functionalization.

We have achieved a sequential hydride-shift-triggered double C(sp3)-H bond functionalization at a position adjacent to an oxygen atom and a benzylic/aliphatic position through the employment of substrates with a dialkyl group in the alkyl chain, which enabled the highly diastereoselective synthesis of fused tetrahydropyrans.