Expanded ring 1,3,5-oxadiazinan-4-ylidene complexes: synthesis and catalysis

Abstract

Here we report the synthesis of new oxygen-containing six-membered ring N-heterocyclic carbene (NHC) ligand precursors. Transitional metal complexes were obtained from these precursors via transmetalation or weak base route along with corresponding thio- and selenoureas. The steric and donor properties of novel expanded ring NHCs (er-NHCs) were investigated and the influence of introducing a heteroatom into a er-NHC was studied using the example of catalytic hydration of internal and terminal alkynes. Additionally, the highest catalytic activity of the 6-OMesAuCl complex in carboxylative cyclization and its potential in CO2 fixation was shown.