Efficient Oxidative Cyclization of 1,6‐Dienes: A Highly Diastereoselective Entry to Substituted Tetrahydropyrans

Widely applicable: Substituted tetrahydropyran products can be obtained in good to high yields and excellent diastereoselectivity by oxidative cyclization of 1,6-dienes (see scheme, PG=protecting group). In situ generated ruthenium tetroxide (1–5 mol %) serves as a catalyst and sodium periodate on wet silica serves as a terminal oxidant. The conversion of a cyclization product into a synthetically useful δ-lactone building block is also presented.