N-heterocyclic carbene catalyzed umpolung of styrenes: mechanistic elucidation and selective tail-to-tail dimerization.
The reaction between N-heterocyclic carbenes (NHCs) and styrenes yields alkyl-substituted azolium salts, which are able to form nucleophilic deoxy Breslow intermediates by simple deprotonation. This hitherto unknown reaction of NHCs represents a new way to generate deoxy Breslow intermediates and paves the way for the selective NHC-catalyzed tail-to-tail homodimerization of styrenes. This reaction significantly broadens the scope of the Michael umpolung and provides a new method to generate 1,4-diaryl compounds.
Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster , Corrensstraße 40, 48149 Münster, Germany.
Michael
M
Schedler
Nathalie E
NE
Wurz
Constantin G
CG
Daniliuc
Frank
F
Glorius