Diastereoselective Formation of Quaternary Stereocenters in Imidazole N-Oxide Cycloaddition with Fluoroalkenes

Imidazole N-oxides are attractive starting materials for the preparation of complex molecules containing an imidazole ring. Dipolar cycloaddition between 1,1-difluoroalkenes and bearing a chiral auxiliary performed in presence oxygen or nitrogen nucleophiles was found to provide access esters amides 2-azaheteroaryl substituent at α position ring as mixtures diastereomers that, most cases, readily separable. This three-component reaction introduces new tertiary quaternary all-carbon stereocenter into heterocyclic originally occupied by hydrogen. Importantly, products trifluoromethyl group attached this available well.