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
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
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
MCH 2(OH) and CH 3OM(M=-, Li, Na) were calculated by means of ab initio method at the MP2/631+G* level. The results show that the metals have the ability to localize charge on O in CH 3OM(M= Li, Na). MCH 2(OH)(M=L...MCH 2(OH) and CH 3OM(M=-, Li, Na) were calculated by means of ab initio method at the MP2/631+G* level. The results show that the metals have the ability to localize charge on O in CH 3OM(M= Li, Na). MCH 2(OH)(M=Li, Na) has four possible structures, among which carbonoxygenbridged structure 1 is the most stable and observable kinetically. For MCH 2(OH)(M=Li, Na), the existence of the metal increases the rigidity of the carbon configuration. This may be the reason why MCH 2(OR)(M=Li, Na) is widely used in stereoselective syntheses.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
β,γ-Unsaturated a-diazocarbonyl compounds possess two reactive sites for electrophilic addition-one at the diazo carbon and the other at the vinylogous γ-position.Controlled by catalyst,divergent transformations ar...β,γ-Unsaturated a-diazocarbonyl compounds possess two reactive sites for electrophilic addition-one at the diazo carbon and the other at the vinylogous γ-position.Controlled by catalyst,divergent transformations are achieved starting from the same starting materials,either by Lewis acid-catalyzed addition or by dirhodium-catalyzed metal carbene reactions.In select cases two catalysts working in combination or in sequence provide a relay for cascade transformations.In this review,we summarize advances in catalyst-dependent divergent transformations of β,γ-unsaturated α-diazocarbonyl compounds and highlight the potential of this exciting research area and the many challenges that remain.展开更多
The nucleophilic trifluoromethylation involving trifluoromethyllithium(LiCF_(3))species has been an open question since Haszeldine attempted to prepare LiCF_(3) in 1949.Indeed,LiCF_(3) has been used for electrophilic ...The nucleophilic trifluoromethylation involving trifluoromethyllithium(LiCF_(3))species has been an open question since Haszeldine attempted to prepare LiCF_(3) in 1949.Indeed,LiCF_(3) has been used for electrophilic difluoromethylene transfer processes(via elimination of fluoride ions)since 2010.Herein,we demonstrated that by using a polar solvent such as dimethylformamide(DMF)or hexamethylphosphoramide(HMPA)as the lithium chelator,the in situ deprotonation of fluoroform(HCF_(3))with lithium hexamethyldisilazide(LiHMDS)could generate a tamed LiCF_(3) species that is sufficiently persistent to undergo nucleophilic trifluoromethylation reaction.The nucleophilic reactivity of LiCF_(3) species was probed with several electrophiles,including arylsulfonyl fluorides,diaryl ketones,and silyl chlorides.The synthetic utility of this method is demonstrated with the efficient synthesis of highly valuable triflones that are otherwise difficult to synthesize from HCF_(3) using potassium or sodium bases.This work not only showcases a new protocol for the utilization of fluoroform(an industrial waste with high global warming potential)as the trifluoromethylation reagent,but also provides intriguing insights into the harnessing of nucleophilic reactivity of the transient LiCF_(3) species.展开更多
ALTHOLIGH carbenoids as the active organometallic intermediates have been widely used in organic syntheses, up to now, only few simple saturated and unsaturated carbenoids, such as H<sub>2</sub>CLiF, Cl<...ALTHOLIGH carbenoids as the active organometallic intermediates have been widely used in organic syntheses, up to now, only few simple saturated and unsaturated carbenoids, such as H<sub>2</sub>CLiF, Cl<sub>3</sub>CLi, HCLiF<sub>2</sub> and HCCLiF, have been studied by theoretical methods.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 possible structures and isomerizations of H 2C C（OH）Li are studied theoretically by the gradient analytical method at RHF/631+G* level. According to these results, reactions of H 2C C（OH）Li with CH 3 + and CH ...The possible structures and isomerizations of H 2C C（OH）Li are studied theoretically by the gradient analytical method at RHF/631+G* level. According to these results, reactions of H 2C C（OH）Li with CH 3 + and CH 3 - are investigated thoroughly. When H 2C C（OH）Li reacts with CH 3 +, H 2C C（OH）Li firstly changes from structure 1 to structure 4, and then combines with CH 3 +. In this reaction, the configuration of central carbon is retained. When H 2C C（OH）Li reacts with CH 3 -, structure 1 firstly breaks its CO bond to give contact ionpair. Then through transition state 16 which is similar to structure 2, the attack of CH 3 - from the opposite side of -OH replaces -OH group and inverts the configuration of carbenoid carbon atom. All the results show that the ambident reactivity of carbenoid has close relationship with the stability of special structures.展开更多
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.
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.
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.
基金Supported by the National Natural Science Foundation of China(No. 29503019,29773025) and the Chinese Uni-versity Doctoral Foun
文摘MCH 2(OH) and CH 3OM(M=-, Li, Na) were calculated by means of ab initio method at the MP2/631+G* level. The results show that the metals have the ability to localize charge on O in CH 3OM(M= Li, Na). MCH 2(OH)(M=Li, Na) has four possible structures, among which carbonoxygenbridged structure 1 is the most stable and observable kinetically. For MCH 2(OH)(M=Li, Na), the existence of the metal increases the rigidity of the carbon configuration. This may be the reason why MCH 2(OR)(M=Li, Na) is widely used in stereoselective syntheses.
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.
基金the National Institutes of Health(No.GM 46503)the National Science Foundation(No.CHE-1212446)the starting funding from Soochow University and Key Laboratory of Organic Synthesis of Jiangsu Province
文摘β,γ-Unsaturated a-diazocarbonyl compounds possess two reactive sites for electrophilic addition-one at the diazo carbon and the other at the vinylogous γ-position.Controlled by catalyst,divergent transformations are achieved starting from the same starting materials,either by Lewis acid-catalyzed addition or by dirhodium-catalyzed metal carbene reactions.In select cases two catalysts working in combination or in sequence provide a relay for cascade transformations.In this review,we summarize advances in catalyst-dependent divergent transformations of β,γ-unsaturated α-diazocarbonyl compounds and highlight the potential of this exciting research area and the many challenges that remain.
基金support of this work by the National Key Research and Development Program of China(2021YFF0701700)the National Natural Science Foundation of China(22271299,22261132514 and 22301308)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB0590000)the Natural Science Foundation of Shandong Province(ZR2021LFG006 and ZR2023LFG003)the Shandong Dongyue Polymer Material Co.Ltd.is gratefully acknowledged。
文摘The nucleophilic trifluoromethylation involving trifluoromethyllithium(LiCF_(3))species has been an open question since Haszeldine attempted to prepare LiCF_(3) in 1949.Indeed,LiCF_(3) has been used for electrophilic difluoromethylene transfer processes(via elimination of fluoride ions)since 2010.Herein,we demonstrated that by using a polar solvent such as dimethylformamide(DMF)or hexamethylphosphoramide(HMPA)as the lithium chelator,the in situ deprotonation of fluoroform(HCF_(3))with lithium hexamethyldisilazide(LiHMDS)could generate a tamed LiCF_(3) species that is sufficiently persistent to undergo nucleophilic trifluoromethylation reaction.The nucleophilic reactivity of LiCF_(3) species was probed with several electrophiles,including arylsulfonyl fluorides,diaryl ketones,and silyl chlorides.The synthetic utility of this method is demonstrated with the efficient synthesis of highly valuable triflones that are otherwise difficult to synthesize from HCF_(3) using potassium or sodium bases.This work not only showcases a new protocol for the utilization of fluoroform(an industrial waste with high global warming potential)as the trifluoromethylation reagent,but also provides intriguing insights into the harnessing of nucleophilic reactivity of the transient LiCF_(3) species.
文摘ALTHOLIGH carbenoids as the active organometallic intermediates have been widely used in organic syntheses, up to now, only few simple saturated and unsaturated carbenoids, such as H<sub>2</sub>CLiF, Cl<sub>3</sub>CLi, HCLiF<sub>2</sub> and HCCLiF, have been studied by theoretical methods.
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 possible structures and isomerizations of H 2C C（OH）Li are studied theoretically by the gradient analytical method at RHF/631+G* level. According to these results, reactions of H 2C C（OH）Li with CH 3 + and CH 3 - are investigated thoroughly. When H 2C C（OH）Li reacts with CH 3 +, H 2C C（OH）Li firstly changes from structure 1 to structure 4, and then combines with CH 3 +. In this reaction, the configuration of central carbon is retained. When H 2C C（OH）Li reacts with CH 3 -, structure 1 firstly breaks its CO bond to give contact ionpair. Then through transition state 16 which is similar to structure 2, the attack of CH 3 - from the opposite side of -OH replaces -OH group and inverts the configuration of carbenoid carbon atom. All the results show that the ambident reactivity of carbenoid has close relationship with the stability of special structures.
