N-Heterocyclic nitrogen Lewis acids are important in synthetic chemistry.Stable cyclic(amino)(aryl)nitrenium cations,cyc-1^(+)-cyc-3^(+),were synthesized by chemical oxidation of aryl azo compounds with different subs...N-Heterocyclic nitrogen Lewis acids are important in synthetic chemistry.Stable cyclic(amino)(aryl)nitrenium cations,cyc-1^(+)-cyc-3^(+),were synthesized by chemical oxidation of aryl azo compounds with different substituents,H and I,at the para positions of the phenyl group.The excited triplet states of cyc-1^(+)-cyc-3^(+) abstract H-atoms step by step to generate radical intermediates cyc-1H^(*+-)cyc-3H^(*+)traced by EPR spectroscopy and products cyc-1H^(2+)-cyc-3H^(2+) characterized by single crystal X-ray diffraction.The Lewis acidity of species cyc-1^(+)-cyc-3^(+) are remote substituent-dependent.Cyc-2^(+)-cyc-3^(+) have much higher acidity than those previously reported congeners based on energies of LUMOs.The electrophilicity enables them to form Lewis adducts with neutral Lewis base Me_(3)P,and to gain one-electron to produce neutral radicals cyc-1^(*)-cyc-3^(*).展开更多
基金the National Key R&D Program of China(Grants 2016YFA0300404 and 2018YFA0306004,X.W.)the National Natural Science Foundation of China(Grants 21525102 and 21690062,X.W.,and 21901005,W.W.)+1 种基金the Natural Science Foundation of Anhui Province(Grant 1908085QB48,W W.)the China Postdoctoral Science Foundation(Grant 2019M651771,W.W.).
文摘N-Heterocyclic nitrogen Lewis acids are important in synthetic chemistry.Stable cyclic(amino)(aryl)nitrenium cations,cyc-1^(+)-cyc-3^(+),were synthesized by chemical oxidation of aryl azo compounds with different substituents,H and I,at the para positions of the phenyl group.The excited triplet states of cyc-1^(+)-cyc-3^(+) abstract H-atoms step by step to generate radical intermediates cyc-1H^(*+-)cyc-3H^(*+)traced by EPR spectroscopy and products cyc-1H^(2+)-cyc-3H^(2+) characterized by single crystal X-ray diffraction.The Lewis acidity of species cyc-1^(+)-cyc-3^(+) are remote substituent-dependent.Cyc-2^(+)-cyc-3^(+) have much higher acidity than those previously reported congeners based on energies of LUMOs.The electrophilicity enables them to form Lewis adducts with neutral Lewis base Me_(3)P,and to gain one-electron to produce neutral radicals cyc-1^(*)-cyc-3^(*).
