Nickel‐Catalyzed Intramolecular 1,2‐Aryl Migration of Mesoionic Carbenes (iMICs)
Arne Merschel, Timo Glodde, Beate Neumann, Hans‐Georg Stammler, Rajendra S. Ghadwal
Abstract
Abstract Intramolecular 1,2‐Dipp migration of seven mesoionic carbenes (iMIC Ar ) 2 a – g (iMIC Ar =ArC{N(Dipp)} 2 CHC; Ar=aryl; Dipp=2,6‐iPr 2 C 6 H 3 ) under nickel catalysis to give 1,3‐imidazoles (IMD Ar ) 3 a – g (IMD Ar =ArC{N(Dipp)CHC(Dipp)N}) has been reported. The formation of 3 indicates the cleavage of an N−C Dipp bond and the subsequent formation of a C−C Dipp bond in 2 , which is unprecedented in NHC chemistry. The use of 3 in accessing super‐iMICs ( 5 ) (S‐iMIC=ArC{N(Dipp)N(Me)C(Dipp)}C) has been shown with selenium ( 6 ), gold ( 7 ), and palladium ( 8 ) compounds. The quantification of the stereoelectronic properties reveals the superior σ‐donor strength of 5 compared to that of classical NHCs. Remarkably, the percentage buried volume of 5 (%V bur =45) is the largest known amongst thus far reported iMICs. Catalytic studies show a remarkable activity of 5 , which is consistent with their auspicious stereoelectronic features.