Synthesis of cis- and trans-2,5-disubstituted tetrahydrofurans by a tandem dihydroxylation-SN2 cyclization sequence.

[reaction: see text] Dihydroxylation of delta- and epsilon-mesyloxy alpha,beta-unsaturated esters proceeds with in situ cyclization to afford 2,5-disubstituted and 2,3,5-trisubstituted tetrahydrofurans.