Chelation-controlled asymmetric aminohalogenation reaction

The chelation-controlled asymmetric aminohalogenation of alpha,beta-unsaturated 3-aryl-N-acyl-N-4-phenyl-2-oxazolidinones have been established by using palladium(II) acetate as the catalyst and as the chelation metal. The reaction is very convenient to perform by simply mixing the three reactants, cinnamates, N,N-dichloro-p-toluenesulfonamide and catalyst together with 4 A molecular sieves at rt in any convenient vial of appropriate size without special protection from inert gases. Unlike the previous asymmetric aminohalogenation, the ionic liquid, [BMINl][NTf2], was found to be superior to [BMIM][BF4] as the reaction media. It was also found that palladium(II) acetate has to be used together with 1 equiv of MeCN to achieve the opposite chelation control. The resulting absolute stereochemistry of the product was unambiguously determined by X-ray structural analysis. (C) 2007 Elsevier Ltd. All rights reserved.