Chiral palladium-pincer complex catalyzed asymmetric condensation of sulfonimines and isocyanoacetate

The asymmetric condensation of isocyanoacetate and sulfonimines was studied. Chiral BINOL and biphenantrol-based palladium-pincer complexes proved to be efficient catalysts affording 2-imidazoline derivatives with up to 86% ee. The level of enantioselectivity was clearly dependent on the gamma-substituents of the BINOL ring. The best results were obtained by using biphenantrol-based pincer-complex catalysts. Some of the complexes induced the selective formation of the anti-diastereorner of the 2-imidazoline. The diastereo- and enantioselectivity showed an interesting solvent dependence as well. It was found that the application of diglyme as a solvent instead of THF leads to preferential formation of the anti product with a slight decrease of the enantioselectivity. (C) 2008 Elsevier Ltd. All rights reserved.