The novel carbenoid H2Ge=CLiF was studied by using the DFT B3LYP and QCISD methods. Geometry optimization calculations indicate that H2Ge=CLiF has three equilibrium configurations, in which the three-membered structur...The novel carbenoid H2Ge=CLiF was studied by using the DFT B3LYP and QCISD methods. Geometry optimization calculations indicate that H2Ge=CLiF has three equilibrium configurations, in which the three-membered structure is the lowest in energy and thus the most stable. Two transition states for isomerization reactions of H2Ge=CLiF were located and the energy barriers were calculated. For the most stable one, the vibrational frequencies and infrared intensities were predicted.展开更多
In order to investigate the reaction mechanism of intramolecular C-H insertion by Rh(II)-mediated carbenoids with trans-(2-phenylcyclopropyl) carbinal radical as the mechanistic probe, diazo compounds 2-(2-phenylcyclo...In order to investigate the reaction mechanism of intramolecular C-H insertion by Rh(II)-mediated carbenoids with trans-(2-phenylcyclopropyl) carbinal radical as the mechanistic probe, diazo compounds 2-(2-phenylcyclopropyl)ethyl diazoacetoacetate 8a and methyl 2-diazo-3oxo-6-(2-phenylcyclopropyl) hexanoate 8b have been synthesized. Preliminary investigation of the intramolecular C-H insertion with Rh2(OAc)4 as catalyst supports a concerted insertion process.展开更多
In order to have efficient and highly stereoselective cyclopropanating reagents, the cyclopropabation reaction of ethylene promoted with Samarium（Ⅱ） carbenoid [Simmons-Smith（SS）reagent] were studied by means of B...In order to have efficient and highly stereoselective cyclopropanating reagents, the cyclopropabation reaction of ethylene promoted with Samarium（Ⅱ） carbenoid [Simmons-Smith（SS）reagent] were studied by means of B3LYP hybrid density functional method. The geometries for reactants, transition states and products are completely optimized. All transition states were verified by the vibrational analysis and the intrinsic reaction coordinate （IRC） calculations. The results showed that, identical with the lithium carbenoid, CH3SmCH2X（X=Cl, Br and Ⅰ） can fairly react with ethylene via both methylene transfer pathway （pathway A） and carbometalation pathway （pathway B）. And the cyclopropanation reaction via methylene transfer pathway proceeds with a lower barrier and at lower temperatures.展开更多
The asymmetric carbenoid C–H insertion of 3-diazooxindoles into 1,4-cyclohexadiene has been accomplished in the presence of chiral bis(imidazoline) NCN pincer iridium(Ⅲ) complexes as the catalysts. With a catalyst l...The asymmetric carbenoid C–H insertion of 3-diazooxindoles into 1,4-cyclohexadiene has been accomplished in the presence of chiral bis(imidazoline) NCN pincer iridium(Ⅲ) complexes as the catalysts. With a catalyst loading of 0.5 mol%, the reactions proceeded smoothly at 0℃ to afford a variety of chiral 3-substituted oxindoles in good yields with moderate to excellent enantioselectivities(up to 99% ee). The protocol exhibits good functional group tolerance with respect to 3-diazooxindoles and is readily scaled up to 2 mmol scale without any loss in activity and enantioselectivity. Density functional theory(DFT)calculations have been performed to better understand the reaction mechanism and to explain the stereochemical outcome of the reactions.展开更多
Ab initlo HF/6-31G* calculations have been performed for the addition mechanism of carbenoid CH2CILi with formaldehyde in tetrahydrofuran. An early complex of formaldehyde with CH2CILi is first formed with quite exoth...Ab initlo HF/6-31G* calculations have been performed for the addition mechanism of carbenoid CH2CILi with formaldehyde in tetrahydrofuran. An early complex of formaldehyde with CH2CILi is first formed with quite exothermic effect. Only a little activation energy of 14.6 kJ/mol is needed for the complex developing into the product through a transition state with coplanar bicyclic structure. In this process, the eletrophilic attack of carbonyl carbon of formaldehyde is more active than the nucleophilic attack of carbon of carbenoid. The exothermal effect of this addition process is up to 216.5 kJ/mol.展开更多
The isomerizations and decompositions of carbenoids H_2C=CLiCl and H_2CLiCl have been studied by use of HF/STO-3G gradient method. Three equilibrium structures of H_2C=CLiCl were obtained, in which the linear structur...The isomerizations and decompositions of carbenoids H_2C=CLiCl and H_2CLiCl have been studied by use of HF/STO-3G gradient method. Three equilibrium structures of H_2C=CLiCl were obtained, in which the linear structure has the lowest energy and the askew substituted structure was the next. It is found that the decomposition of H_2C=CLiCl undergoes a concerted FBW rearrangement and the inversion barrier of its askew substituted structure is 36 kJ/mol. For H_2CLiCl, the askew substituted structure, extending all valences of the carbon into a single hemisphere, is the lowest energy and its inversion barrier is 87 kJ/mol. The discussions on the factors concerned with the structural stabilities are given in this paper.展开更多
文摘The novel carbenoid H2Ge=CLiF was studied by using the DFT B3LYP and QCISD methods. Geometry optimization calculations indicate that H2Ge=CLiF has three equilibrium configurations, in which the three-membered structure is the lowest in energy and thus the most stable. Two transition states for isomerization reactions of H2Ge=CLiF were located and the energy barriers were calculated. For the most stable one, the vibrational frequencies and infrared intensities were predicted.
文摘In order to investigate the reaction mechanism of intramolecular C-H insertion by Rh(II)-mediated carbenoids with trans-(2-phenylcyclopropyl) carbinal radical as the mechanistic probe, diazo compounds 2-(2-phenylcyclopropyl)ethyl diazoacetoacetate 8a and methyl 2-diazo-3oxo-6-(2-phenylcyclopropyl) hexanoate 8b have been synthesized. Preliminary investigation of the intramolecular C-H insertion with Rh2(OAc)4 as catalyst supports a concerted insertion process.
基金This work was supported by the Northwest Normal University Science Foundation of Gansu Province （No. NWNU-QN-2001-08）.
文摘In order to have efficient and highly stereoselective cyclopropanating reagents, the cyclopropabation reaction of ethylene promoted with Samarium（Ⅱ） carbenoid [Simmons-Smith（SS）reagent] were studied by means of B3LYP hybrid density functional method. The geometries for reactants, transition states and products are completely optimized. All transition states were verified by the vibrational analysis and the intrinsic reaction coordinate （IRC） calculations. The results showed that, identical with the lithium carbenoid, CH3SmCH2X（X=Cl, Br and Ⅰ） can fairly react with ethylene via both methylene transfer pathway （pathway A） and carbometalation pathway （pathway B）. And the cyclopropanation reaction via methylene transfer pathway proceeds with a lower barrier and at lower temperatures.
基金supported by a grant from the National Nat-ural Science Foundation of China(No.21472176).
文摘The asymmetric carbenoid C–H insertion of 3-diazooxindoles into 1,4-cyclohexadiene has been accomplished in the presence of chiral bis(imidazoline) NCN pincer iridium(Ⅲ) complexes as the catalysts. With a catalyst loading of 0.5 mol%, the reactions proceeded smoothly at 0℃ to afford a variety of chiral 3-substituted oxindoles in good yields with moderate to excellent enantioselectivities(up to 99% ee). The protocol exhibits good functional group tolerance with respect to 3-diazooxindoles and is readily scaled up to 2 mmol scale without any loss in activity and enantioselectivity. Density functional theory(DFT)calculations have been performed to better understand the reaction mechanism and to explain the stereochemical outcome of the reactions.
文摘Ab initlo HF/6-31G* calculations have been performed for the addition mechanism of carbenoid CH2CILi with formaldehyde in tetrahydrofuran. An early complex of formaldehyde with CH2CILi is first formed with quite exothermic effect. Only a little activation energy of 14.6 kJ/mol is needed for the complex developing into the product through a transition state with coplanar bicyclic structure. In this process, the eletrophilic attack of carbonyl carbon of formaldehyde is more active than the nucleophilic attack of carbon of carbenoid. The exothermal effect of this addition process is up to 216.5 kJ/mol.
文摘The isomerizations and decompositions of carbenoids H_2C=CLiCl and H_2CLiCl have been studied by use of HF/STO-3G gradient method. Three equilibrium structures of H_2C=CLiCl were obtained, in which the linear structure has the lowest energy and the askew substituted structure was the next. It is found that the decomposition of H_2C=CLiCl undergoes a concerted FBW rearrangement and the inversion barrier of its askew substituted structure is 36 kJ/mol. For H_2CLiCl, the askew substituted structure, extending all valences of the carbon into a single hemisphere, is the lowest energy and its inversion barrier is 87 kJ/mol. The discussions on the factors concerned with the structural stabilities are given in this paper.
