Compared to well-established 1,5-HAT of N-centered radicals,the synthetic applications of 1,2-HAT process were scarce due to the high barrier and constrained three-membered transition state.Here,we have developed a no...Compared to well-established 1,5-HAT of N-centered radicals,the synthetic applications of 1,2-HAT process were scarce due to the high barrier and constrained three-membered transition state.Here,we have developed a novel C(sp')-H gem-difluoroallylation via a base assisted formal 1,2-HAT of amidyl radicals with the reductive quenching cycle of photocatalyst.This transformation enables the efficient formation ofα-aminoalkyl radicals via 1,2-HAT and showcases good functional group tolerance.Our preliminary mechanistic experiments,along withDensity Functional Theory(DFT)calculations demonstrate thefeasibility of 1,2-HAT of amidyl radicals,especially when assisted by a base.Furthermore,our method also succeeds in the Giese addition of electron-deficient alkenes as well as styrene.展开更多
As the cross-coupling needs of chemists continue to grow for accessing increasingly complex targets,radical-based transformations have become mainstay methodologies for the discovery of new reactivity under mild and w...As the cross-coupling needs of chemists continue to grow for accessing increasingly complex targets,radical-based transformations have become mainstay methodologies for the discovery of new reactivity under mild and wastelimiting conditions.En route to such methodological advancements,the observation of the 1,2-boron shift a novel radical rearrangement in its application has generated a new cross-coupling methodology to access products that were previously inaccessible or otherwise cumbersome to make.The origins of this radical rearrangement along with the synthetic applications to organic chemistry are highlighted.展开更多
A new oleanolic acid derivative with A-ring lactone,C-ring rearrangement and decarboxylation at C28 was synthesized,which was confirmed by HRMS,NMR and X-ray crystal structure.It is the first report about the methyl r...A new oleanolic acid derivative with A-ring lactone,C-ring rearrangement and decarboxylation at C28 was synthesized,which was confirmed by HRMS,NMR and X-ray crystal structure.It is the first report about the methyl rearrangement on C-ring of oleanolic phenylmethyl ester,and the possible mechanism was proposed as the 1,2-methyl shift.展开更多
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 ab initio calculations have been performed on the reaction paths of 1,2-H shift and inversion processes of amino-carbene molecule by the Intrinsic Reaction Coordinate(IRC)method. We have determined the equilibrium...The ab initio calculations have been performed on the reaction paths of 1,2-H shift and inversion processes of amino-carbene molecule by the Intrinsic Reaction Coordinate(IRC)method. We have determined the equilibrium geometries and energies of the reactant,transition state and product,and obtained the activation energies,reaction heats,frequency factors and the activation entropies of these two reaction processes.The vibrational correlation from reactant to transition state indicated that the IRCs of 1,2-H shift and inversion processes were associated with the deformation modes of 1540 and 1208 cm^(-1),respectively.The vibrational coupling between normal coordinates in the inversion process would be helpful for selecting the inversion reaction channel.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
基金We thank the National Natural Science Foundation of China(22001233)Zhejiang Provincial Ten Thousand Talent Program(2020R52021)and Zhejiang Normal University for financial support.
文摘Compared to well-established 1,5-HAT of N-centered radicals,the synthetic applications of 1,2-HAT process were scarce due to the high barrier and constrained three-membered transition state.Here,we have developed a novel C(sp')-H gem-difluoroallylation via a base assisted formal 1,2-HAT of amidyl radicals with the reductive quenching cycle of photocatalyst.This transformation enables the efficient formation ofα-aminoalkyl radicals via 1,2-HAT and showcases good functional group tolerance.Our preliminary mechanistic experiments,along withDensity Functional Theory(DFT)calculations demonstrate thefeasibility of 1,2-HAT of amidyl radicals,especially when assisted by a base.Furthermore,our method also succeeds in the Giese addition of electron-deficient alkenes as well as styrene.
文摘As the cross-coupling needs of chemists continue to grow for accessing increasingly complex targets,radical-based transformations have become mainstay methodologies for the discovery of new reactivity under mild and wastelimiting conditions.En route to such methodological advancements,the observation of the 1,2-boron shift a novel radical rearrangement in its application has generated a new cross-coupling methodology to access products that were previously inaccessible or otherwise cumbersome to make.The origins of this radical rearrangement along with the synthetic applications to organic chemistry are highlighted.
基金The project was supported by NSFC(No.21172130)and NBRPC(973 Program,No.2012CB821600).
文摘A new oleanolic acid derivative with A-ring lactone,C-ring rearrangement and decarboxylation at C28 was synthesized,which was confirmed by HRMS,NMR and X-ray crystal structure.It is the first report about the methyl rearrangement on C-ring of oleanolic phenylmethyl ester,and the possible mechanism was proposed as the 1,2-methyl shift.
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.
基金This project was supported by the National Natural Science Foundation of China.
文摘The ab initio calculations have been performed on the reaction paths of 1,2-H shift and inversion processes of amino-carbene molecule by the Intrinsic Reaction Coordinate(IRC)method. We have determined the equilibrium geometries and energies of the reactant,transition state and product,and obtained the activation energies,reaction heats,frequency factors and the activation entropies of these two reaction processes.The vibrational correlation from reactant to transition state indicated that the IRCs of 1,2-H shift and inversion processes were associated with the deformation modes of 1540 and 1208 cm^(-1),respectively.The vibrational coupling between normal coordinates in the inversion process would be helpful for selecting the inversion reaction channel.
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.
