Merschel Arne, Glodde Timo, Neumann Beate, Stammler Hans-Georg, Ghadwal Rajendra S
Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld, Universitätsstrasse 25, 33615, Bielefeld, Germany.
Angew Chem Int Ed Engl. 2021 Feb 8;60(6):2969-2973. doi: 10.1002/anie.202014328. Epub 2020 Dec 11.
Intramolecular 1,2-Dipp migration of seven mesoionic carbenes (iMIC ) 2 a-g (iMIC =ArC{N(Dipp)} CHC; Ar=aryl; Dipp=2,6-iPr C H ) under nickel catalysis to give 1,3-imidazoles (IMD ) 3 a-g (IMD =ArC{N(Dipp)CHC(Dipp)N}) has been reported. The formation of 3 indicates the cleavage of an N-C bond and the subsequent formation of a C-C 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 =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.
据报道，在镍催化下，七种中氮茚基卡宾（iMIC）2 a - g（iMIC = ArC{N(Dipp)}CHC；Ar = 芳基；Dipp = 2,6 - iPr₂C₆H₃）发生分子内1,2 - Dipp迁移，生成1,3 - 咪唑（IMD）3 a - g（IMD = ArC{N(Dipp)CHC(Dipp)N}）。3的形成表明2中N - C键的断裂以及随后C - C键的形成，这在氮杂环卡宾化学中是前所未有的。已证明3可用于制备超级中氮茚基卡宾（5）（S - iMIC = ArC{N(Dipp)N(Me)C(Dipp)}C），分别与硒（6）、金（7）和钯（8）化合物反应。对立体电子性质的量化表明，与经典氮杂环卡宾相比，5具有更强的σ供体强度。值得注意的是，5的掩埋体积百分比（%Vbur = 45）是迄今为止报道的中氮茚基卡宾中已知最大的。催化研究表明5具有显著的活性，这与其良好的立体电子特性一致。
