β-Hydroxy-α-tosyloxy esters as chiral building blocks for the enantioselective synthesis of benzo-annulated oxa-heterocycles: scope and limitations

The enantioselective synthesis of benzo-annulated oxa-heterocycles 2,3-dihydrobenzofuran and 1-benzopyran derivatives is described using β-hydroxy-α-tosyloxy esters as chiral building blocks, which are easily accessible through the regioselective α-tosylation of Sharpless asymmetric dihydroxylation-derived syn-2,3-dihydroxy esters.