Acyl Protection Strategy for Synthesis of a Protic NHC Complex via N-Acyl Methanolysis

In a new strategy for the synthesis of protic NHC complexes, iridium
and rhodium complexes of N-benzoyl-substituted NHCs are first generated
by direct deprotonation of an acyl-protected imidazolium salt. Deprotection
of the acyl group with methanol then gives methyl benzoate and the
protic NHC. This sequence represents a new strategy for the synthesis
of protic NHC complexes. We expect this strategy to have useful generality.