Solvent-Free Asymmetric Anhydride Opening in a Ball Mill

The mechanochemical technique of ball milling has been applied to the asymmetric opening of meso-anhydrides, mediated by the cinchona alkaloid quinidine. A simple workup procedure affords the products, optically active dicarboxylic acid monoesters, in high yields, with up to 64% ee. With most substrates no column chromatography was needed. A range of various alcohols, as well as anhydrides, reacted well thus demonstrating the scope of this methodology. Even mixtures of purely solid components react, and no solvent is required (except during the workup). The possible use of almost equimolar amounts of starting materials significantly simplifies the product isolation compared to the standard solution reaction.