Mechanism of 1,2-shift through π-complex transition state  

作　　者：戴乾圜 周志刚 张大平 

机构地区：[1]Center of Chemical and Bioengineering of Cancer Research , Beijing Polytechnic University, Beijing 100022, China

出　　处：《Science China Chemistry》2000年第6期576-586,共11页中国科学（化学英文版）

摘　　要：A systematic calculation of the potential curves or surfaces for 1,2-shift has been realized by using MNDO or other models in MOPAC programs. By referring to the previous author’ viewpoints, the 1,2-shift can be divided into two categories. 1,2-electron-deficient shift is that the electronic configuration of the atom which accepts the migrating group is a cation or an electron-deficient atom, and 1,2-anion shift is the one that the accepted atom of the migration group is a negative ion. In terms of the experimental facts and the calculation of the potential surfaces, in electron-deficient shift such as Beckmann or Baeyer-Villiger rearrangement, the migration occurs through a transition complex formed between the π-bond and the cation or electron-deficient migrating group, but in anion shift such as Wittig or Stevens rearrangement, the electron pair in π-orbit excites at first to π orbit, and then the migration occurs through the new formed complex between the anion migration group and the vacant π orbit. The above mechanisms explain reasonably the intramolecular properties, the configuration retentions of the migration group, and the corresponding migratory aptitudes of the two type 1, 2-shifts. The partial and less important free radical reaction of 1, 2-anion shift has been explained by the π-complex mechanism too.A systematic calculation of the potential curves or surfaces for 1,2-shift has been realized by using MNDO or other models in MOPAC programs. By referring to the previous authors’ viewpoints, the 1,2-shift can be divided into two categories. 1,2-electron-deficient shift is that the electronic configuration of the atom which accepts the migrating group is a cation or an electron-deficient atom, and 1,2-anion shift is the one that the accepted atom of the migration group is a negative ion. In terms of the experimental facts and the calculation of the potential surfaces, in electron-deficient shift such as Beckmann or Baeyer-Villiger rearrangement, the migration occurs through a transition complex formed between the 7i-bond and the cation or electron-deficient migrating group, but in anion shift such as Wittig or Stevens rearrangement, the electron pair in it-orbit excites at first to π* orbit, and then the migration occurs through the new formed complex between the anion migration group and the vacant

关 键 词：1 2-shift REARRANGEMENT MNDO potential surface π-complex WITTIG rearrangement. 

分 类 号：O621.3[理学—有机化学]