β-hydroxy-α-tosyloxy esters as chiral building blocks for the enantio selective 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 beta-hydroxy-alpha-tosyloxy esters as chiral building blocks, which are easily accessible through the regioselective alpha-tosylation of Sharpless asymmetric dihydroxylation-derived syn-2,3-dihydroxy esters. (c) 2008 Elsevier Ltd. All rights reserved.