Efficient general asymmetric syntheses of 3-substituted 1(3H)-isobenzofuranones in very high enantiomeric excess

Article abstract of DOI:10.1016/0040-4039(96)00260-2

The intermolecular asymmetric reduction of methyl o-(1-oxoalkyl)benzoates with B-chlorodiisopinocampheylborane provides, after workup, 3-alkylphthalides in ≥ 97% ee. Unfortunately, this procedure is not as efficient for the preparation of 3-arylphthalides. However, an intramolecular reduction of B-(o-benzoylbenzoyloxy)diisopinocampheylborane, readily prepared by the treatment of o-benzoyl benzoic acid with diisopinocampheylborane, provides 3-phenylphthalide in ≥ 96% ee.