Solvent resistant nanofiltration of enlarged (NHC)Pd(allyl)Cl-Complexes for cross coupling reactions

Abstract

An enlarged imidazolinium salt with a molecular mass of nearly 800 g/mol was synthesized and the respective N-heterocyclic carbene (NHC= N,N’-bis(2,6-diisopropyl-4-CH2NCy2- phenyl)-4,5-dihydroimidazol-2-ylidene) converted into (NHC)Pd(allyl)Cl and (NHC)Pd(cinnamyl)Cl complexes. The cinnamyl complex displays excellent activities in the Suzuki-Miyaura coupling and the Buchwald-Hartwig amination. The separation of this complex from the coupling products by means of a solvent resistant nanofiltration using a PDMS (poly-dimethylsiloxane) membrane on PAN (polyacrylonitrile) was tested and very high retention of between 97% and 99.9% of the (NHC)Pd complex observed. The residual Pd content in the cross coupling products is in the range of 3.5 - 25ppm.