This paper is dedicated to Stephen Buchwald,agood friend and eminent scientist, on the occasion of his6 0th birthday.Supporting information for this article is availableonthe WWW under http://dx.doi.org/10.1002/adsc.201500224.
Abstract:In extension of ac oncept of Lloyd-Jones, based on the combination of ar acemic catalyst with as calemic substrate,w eh aver ecently developed am ethod for determining the enantioselectivity of ac hiral catalyst from its racemic form by mass spectrometric screeningo fanon-equal mixture of two mass-labeled quasi-enantiomeric substrates.A fter an initial proof of principle using palladium-catalyzed allylic substitution as test reaction, we report now the successful applicationo ft his approacht ot he screeningo fc hiral aminesa sc atalysts for the enantioselective Michaela ddition to a,b-unsaturated aldehydes.T he results confirmt hat our method allows fast and reliable evaluation of chiral racemic catalysts.T his opens up new possibilities for investigating catalyst structures that are not easily available in enantiomerically pure form.