N-heterocyclic carbene complexes of Silver(I) for C-C bond activation of alkylnitriles and catalytic oxazoline synthesis
N-heterocyclic carbenes (NHCs) are increasingly prevalent ligands for the synthesis of organometallic complexes and in homogeneous catalysis [1]. Reaction of azolium salts with Ag2O afford Ag–NHC complexes, which are commonly transmetallated in situ to different metals [2]. However, to date little attention has been paid to the Ag–NHC intermediates regarding complex formation and potential catalytic applications [3].
We describe that generation of Ag–NHC complexes from azolium salts in refluxing CH3CN results in a selective C–C bond cleavage and formation of [(NHC)Ag(CN)] complexes; which can also be extended to other alkyl nitrile reagents [4].
Additionally, we will present the catalytic performances of a series of Ag–NHC complexes for the synthesis of oxazolines via aldol condensation. These highly active systems reveal relatively unexplored applications of easily accessible silver carbene complexes.
[1] A. J. Arduengo and G. Bertrand, Chem. Rev., 2009, 109, 3209-3210.
[2] J. C. Garrison and W. J. Youngs, Chem. Rev., 2005, 105, 3978-4008.
[3] (a) J. Ramirez, R. Corberan, M. Sanau, E. Peris and E. Fernandez, Chem. Commun., 2005, 3056-3058; (b) M.-T. Chen, B. Landers and O. Navarro, Org. Biomol. Chem., 2012, 10, 2206-2208.
[4] R. Heath, H. Muller-Bunz, M. Albrecht, Chem. Commun., 2015, 51, 8600-8701.