The O- to C-carboxyl transfer of oxazolyl carbonates promoted by triazolinylidenes, generated in situ with NEt3, shows a markedly different rate and chemoselectivity profile to the same reaction promoted by triazolinylidenes generated using KHMDS. The mechanism of these pathways has been probed through extensive crossover studies to understand this process. The use of NEt3 as a base allows domino multi-step reaction sequences to be developed, although chiral NHCs only generate modest levels of asymmetric induction (<15% ee) in these domino reaction processes.
