Selective 3,3-Rearrangement of Azobenzenes upon Complexation by a Frustrated Lewis Pair |
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| Authors: | Dr Lucas Wickemeyer Prof Dr Israel Fernández Beate Neumann Dr Hans-Georg Stammler Prof Dr Norbert W Mitzel |
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| Institution: | 1. Lehrstuhl für Anorganische Chemie und Strukturchemie and Centrum für Molekulare Materialen CM2, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, 33615 Bielefeld, Germany;2. Departamento de Química Orgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria, 28040 Madrid, Spain |
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| Abstract: | The reaction of the oxygen-bridged frustrated Lewis pairs (FLPs) tBu2P−O−Si(C2F5)3 ( 1 ) and tBu2P−O−AlBis2 ( 2 ) with azobenzene, promoted by UV irradiation, led to a selective complexation of the cis-isomer. The addition product of 2 is stable, while the adduct of 1 isomerizes in solution in an ortho-benzidine-like 3,3]-rearrangement by cleavage of the N−N bond, saturation of the nitrogen atoms with hydrogen atoms and formation of a new bond between two phenyl ortho-carbon atoms. Similar rearrangements take place with different para-substituted azobenzenes (R=Me, OMe, Cl) and di(2-naphthyl)diazene, while ortho-methylated azo compounds do not form adducts with 1 . All adducts were characterized by multinuclear NMR spectroscopy and elemental analyses and the mechanism of the rearrangement was explored by quantum-chemical calculations. |
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| Keywords: | Azobenzene Benzidine Frustrated Lewis Pairs Molecular Activation Rearrangements |
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