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 divi...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.展开更多
Using a catalytic amount of Nal and a stoichiometric oxidant Oxone-@,a convenient procedure has been developed for the catalytic oxidative 1,2-shift of arylalkenes in CH3CN/H2O at room temperature,which provides the c...Using a catalytic amount of Nal and a stoichiometric oxidant Oxone-@,a convenient procedure has been developed for the catalytic oxidative 1,2-shift of arylalkenes in CH3CN/H2O at room temperature,which provides the corresponding α-aryl ketones in moderate to good yields.In this protocol,sodium iodide is first oxidized into hypoiodous acid,which reacts with arylalkene to afford iodohydrin.Then,the iodohydrin is transformed into the α-aryl ketone via an oxidative 1,2-shift rearrangement.展开更多
The mechanism of Rh（Ⅱ） carbene S-H insertion into H2S in gas phase has been studied by B3LYP functional. Calculation results showed that the Rh（Ⅱ） carbene S-H insertion into H2S took only stepwise channels and n...The mechanism of Rh（Ⅱ） carbene S-H insertion into H2S in gas phase has been studied by B3LYP functional. Calculation results showed that the Rh（Ⅱ） carbene S-H insertion into H2S took only stepwise channels and no concerted channels had been located, which was different from the Rh（Ⅱ） carbene C-H and O-H insertions.展开更多
The mechanisms of insertion of O-H bond of Rh（ Ⅱ ）-methylene carbene into methanol and ethanol were studied by using B3LYP functional both in gas phase and in CH2 C12. The formation of free alcoholic oxonium ylides...The mechanisms of insertion of O-H bond of Rh（ Ⅱ ）-methylene carbene into methanol and ethanol were studied by using B3LYP functional both in gas phase and in CH2 C12. The formation of free alcoholic oxonium ylides is found to be impossible. Alcoholic oxonium ylide are formed as the intermediates before beth the stepwise and the concerted transition states of insertion of O-H bend of Rh（ Ⅱ ）-methylene carbene into methanol and ethanol. With re- gard to the mechanisms of insertion of O-H of Rh（ Ⅱ ） -methylene carbene into alcohols, analysis of the energy bartiers of the two mechanisms indicate that the stepwise mechanism is more plausible than the concerted mechanism.展开更多
文摘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.
基金Financial support from the National Natural Science Foundation of China(No.21072176) is greatly appreciated
文摘Using a catalytic amount of Nal and a stoichiometric oxidant Oxone-@,a convenient procedure has been developed for the catalytic oxidative 1,2-shift of arylalkenes in CH3CN/H2O at room temperature,which provides the corresponding α-aryl ketones in moderate to good yields.In this protocol,sodium iodide is first oxidized into hypoiodous acid,which reacts with arylalkene to afford iodohydrin.Then,the iodohydrin is transformed into the α-aryl ketone via an oxidative 1,2-shift rearrangement.
文摘The mechanism of Rh（Ⅱ） carbene S-H insertion into H2S in gas phase has been studied by B3LYP functional. Calculation results showed that the Rh（Ⅱ） carbene S-H insertion into H2S took only stepwise channels and no concerted channels had been located, which was different from the Rh（Ⅱ） carbene C-H and O-H insertions.
文摘The mechanisms of insertion of O-H bond of Rh（ Ⅱ ）-methylene carbene into methanol and ethanol were studied by using B3LYP functional both in gas phase and in CH2 C12. The formation of free alcoholic oxonium ylides is found to be impossible. Alcoholic oxonium ylide are formed as the intermediates before beth the stepwise and the concerted transition states of insertion of O-H bend of Rh（ Ⅱ ）-methylene carbene into methanol and ethanol. With re- gard to the mechanisms of insertion of O-H of Rh（ Ⅱ ） -methylene carbene into alcohols, analysis of the energy bartiers of the two mechanisms indicate that the stepwise mechanism is more plausible than the concerted mechanism.
