Binuclear aluminum alkyl complexes 2a–4g supported by linked bis（β-diketiminate） ligands were synthesized via the reaction of AlEt3 or AlMe3 and the corresponding proligand in a 2：1 molar ratio with moderate yiel...Binuclear aluminum alkyl complexes 2a–4g supported by linked bis（β-diketiminate） ligands were synthesized via the reaction of AlEt3 or AlMe3 and the corresponding proligand in a 2：1 molar ratio with moderate yields. The isolated complexes were well-characterized by ^1H-NMR, ^13C-NMR and elemental analysis. The binuclear nature of aluminum complex 2b was further confirmed by an X-ray diffraction study. All complexes 2a–4g could efficiently initiate the ring-opening polymerization（ROP） of ε-caprolactone in toluene. The substituents at the aromatic rings and the linker unit in the auxiliary ligands exerted significant influence on the catalytic behavior of the investigated aluminum complexes. Complex 4g（R^1 = R^2 = Cl） containing propylenyl bridging unit exhibited the highest catalytic activity among these complexes, which might be attributed to the increased electrophilicity of the metal center as well as more opened coordination sphere. The molecular weights of obtained poly（ε-caprolactone）s deviating considerably from the theoretical values indicated that the ROP of ε-caprolactone by complexes 2a–4g was not well-controlled, which was also judged from the broad molecular weight distributions（MWD = 1.47-2.47） of produced poly（ε-caprolactone）s. These complexes proved to be inactive toward the polymerization of rac-lactide alone. In the presence of alcohol the polymerization occurred, which was actually initiated by the decomposition species of the aluminum complex upon the treatment with isopropanol.展开更多
Coordination-insertion ring-opening polymerization(ROP)of cyclic esters is an industrial way to synthesize polyesters,which are widely applied in biomedical and environment-benign fields.However,the rate-determining t...Coordination-insertion ring-opening polymerization(ROP)of cyclic esters is an industrial way to synthesize polyesters,which are widely applied in biomedical and environment-benign fields.However,the rate-determining transition state(TS)identified by the conventional reaction pathways(pathway A and pathway B)presented in the literature did not well describe the structure-reactivity relationship.The misidentification of the rate-determining TS might arise from the less ergodicity in the search of reaction pathways.Herein,we suggested a stride strategy based on the insight that even a partial double bond is rotatable at the catalysis temperature.As a result,we revealed a new reaction pathway,pathway C with a torsion transition state TSC2,by density functional theory(DFT).We also carried out kinetic experiments of ROP of D-lactide(D-LA),L-lactide(L-LA),ε-caprolactone(CL),andδ-valerolactone(VL),using poly(ethylene glycol)as the initiator and stannous octoate as the catalyst.The excellent linearity between the calculated free energy barriers and logarithms of the experimental kinetic constants of the two kinds of lactide and lactone monomers,was established,validating the quasi-ergodic search of reaction pathways and the scaling predicted by transition state theory.The linearity was highly predictive for the other lactide and lactone monomers,demonstrated by glycolide(GA)and trimethylene urethane(TU).展开更多
A method for the analysis of the relationship between the helical structure and optical activity was proposed by the study of the conformations and X-ray diffraction structures of some cyclic esters prepared by esteri...A method for the analysis of the relationship between the helical structure and optical activity was proposed by the study of the conformations and X-ray diffraction structures of some cyclic esters prepared by esterification of L-(-)-2.3-O-methylidene threitol and L-(+)-2,3-O-isopropplidene threitol with alkanedioyl dichlorides and o-,m-,and p-phthaloyl dichlorides.展开更多
A homologous series of cyclic esters was used as a model for studying and clarifying the relationship between the helical structure and optical activity.
A new compound. methyl 4. 6-O-benzylidene-a-D-glucopyranoside 2. 3-cyclicphosphite ethyl ester was synthesized via the reaction of methyl 4. 6-O-benzylidene-a-D-glucopyranoside and ethyl dichlorophosphite. Its structu...A new compound. methyl 4. 6-O-benzylidene-a-D-glucopyranoside 2. 3-cyclicphosphite ethyl ester was synthesized via the reaction of methyl 4. 6-O-benzylidene-a-D-glucopyranoside and ethyl dichlorophosphite. Its structure was confirmed by NMR and MSspectral methods.展开更多
α, α′ -Dioxo (ester ) ketene cyclic S, S-acetais 2 were reacted withethyleneddriine to chrd α, α′-dioxo (ester)ketene cyclic N, N-acetals 3 Thisprocess provides a new method for the synthesis of 3 in gnd yteld u...α, α′ -Dioxo (ester ) ketene cyclic S, S-acetais 2 were reacted withethyleneddriine to chrd α, α′-dioxo (ester)ketene cyclic N, N-acetals 3 Thisprocess provides a new method for the synthesis of 3 in gnd yteld under mildcondition. All products are confirmed with elementai analpeis, IR, 1H NMR and13~C NMR展开更多
Several cyclic amino acids (1-4) were synthesized from glycine. Isocyanate ester was prepared as the key intermediate and reacted with dibromoalkanes to afford the target compounds.
This paper described the first example of polyamidoamine dendrimers ester(PAMAM) used as a gel electrolyte with a short-chain polyethylene glycol (MPEG-400) as aplasticizer. The polymer films are solid and sticky. Bac...This paper described the first example of polyamidoamine dendrimers ester(PAMAM) used as a gel electrolyte with a short-chain polyethylene glycol (MPEG-400) as aplasticizer. The polymer films are solid and sticky. Background cyclic voltammetry (CV) shows apotential window between +0.7 and -0.7 V vs. Ag/AgCl. The voltammetry of ferrocene and7,7,8,8-tetracyanoquinodimethane (TCNQ) indicates that diffusion coefficients are in the range of10^(-8) -10^(-9) cm^2/s. Ionic conductivities are approximately 10^(-6) S/cm. Similar films usingdimethyl sulfoxide (DMSO) as a plasticizer instead of MPEG-400 have demonstrated ionicconductivities of 10^(-4) S/cm and reversible voltammetry. However, UV spectropho-tometry shows that70% of the DMSO is lost under vacuum, indicating the difficulty in quantifying the DMSO contentwhen exposed to vacuum.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos. 20604009 and 21474028)
文摘Binuclear aluminum alkyl complexes 2a–4g supported by linked bis（β-diketiminate） ligands were synthesized via the reaction of AlEt3 or AlMe3 and the corresponding proligand in a 2：1 molar ratio with moderate yields. The isolated complexes were well-characterized by ^1H-NMR, ^13C-NMR and elemental analysis. The binuclear nature of aluminum complex 2b was further confirmed by an X-ray diffraction study. All complexes 2a–4g could efficiently initiate the ring-opening polymerization（ROP） of ε-caprolactone in toluene. The substituents at the aromatic rings and the linker unit in the auxiliary ligands exerted significant influence on the catalytic behavior of the investigated aluminum complexes. Complex 4g（R^1 = R^2 = Cl） containing propylenyl bridging unit exhibited the highest catalytic activity among these complexes, which might be attributed to the increased electrophilicity of the metal center as well as more opened coordination sphere. The molecular weights of obtained poly（ε-caprolactone）s deviating considerably from the theoretical values indicated that the ROP of ε-caprolactone by complexes 2a–4g was not well-controlled, which was also judged from the broad molecular weight distributions（MWD = 1.47-2.47） of produced poly（ε-caprolactone）s. These complexes proved to be inactive toward the polymerization of rac-lactide alone. In the presence of alcohol the polymerization occurred, which was actually initiated by the decomposition species of the aluminum complex upon the treatment with isopropanol.
基金financially supported by the National Natural Science Foundation of China(No.52130302)。
文摘Coordination-insertion ring-opening polymerization(ROP)of cyclic esters is an industrial way to synthesize polyesters,which are widely applied in biomedical and environment-benign fields.However,the rate-determining transition state(TS)identified by the conventional reaction pathways(pathway A and pathway B)presented in the literature did not well describe the structure-reactivity relationship.The misidentification of the rate-determining TS might arise from the less ergodicity in the search of reaction pathways.Herein,we suggested a stride strategy based on the insight that even a partial double bond is rotatable at the catalysis temperature.As a result,we revealed a new reaction pathway,pathway C with a torsion transition state TSC2,by density functional theory(DFT).We also carried out kinetic experiments of ROP of D-lactide(D-LA),L-lactide(L-LA),ε-caprolactone(CL),andδ-valerolactone(VL),using poly(ethylene glycol)as the initiator and stannous octoate as the catalyst.The excellent linearity between the calculated free energy barriers and logarithms of the experimental kinetic constants of the two kinds of lactide and lactone monomers,was established,validating the quasi-ergodic search of reaction pathways and the scaling predicted by transition state theory.The linearity was highly predictive for the other lactide and lactone monomers,demonstrated by glycolide(GA)and trimethylene urethane(TU).
文摘A method for the analysis of the relationship between the helical structure and optical activity was proposed by the study of the conformations and X-ray diffraction structures of some cyclic esters prepared by esterification of L-(-)-2.3-O-methylidene threitol and L-(+)-2,3-O-isopropplidene threitol with alkanedioyl dichlorides and o-,m-,and p-phthaloyl dichlorides.
文摘A homologous series of cyclic esters was used as a model for studying and clarifying the relationship between the helical structure and optical activity.
文摘A new compound. methyl 4. 6-O-benzylidene-a-D-glucopyranoside 2. 3-cyclicphosphite ethyl ester was synthesized via the reaction of methyl 4. 6-O-benzylidene-a-D-glucopyranoside and ethyl dichlorophosphite. Its structure was confirmed by NMR and MSspectral methods.
文摘α, α′ -Dioxo (ester ) ketene cyclic S, S-acetais 2 were reacted withethyleneddriine to chrd α, α′-dioxo (ester)ketene cyclic N, N-acetals 3 Thisprocess provides a new method for the synthesis of 3 in gnd yteld under mildcondition. All products are confirmed with elementai analpeis, IR, 1H NMR and13~C NMR
基金the National Natural Science Foundation of China(No.20272001)
文摘Several cyclic amino acids (1-4) were synthesized from glycine. Isocyanate ester was prepared as the key intermediate and reacted with dibromoalkanes to afford the target compounds.
基金This work was financially supported by the National Natural Science Foundation of China (No. 29875018) the Natural Science Foundation of Gansu Province (No. ZS991-A25-008-Z)the Doctorate Foundation of Northwestern Politech-nical University (No. CX200
文摘This paper described the first example of polyamidoamine dendrimers ester(PAMAM) used as a gel electrolyte with a short-chain polyethylene glycol (MPEG-400) as aplasticizer. The polymer films are solid and sticky. Background cyclic voltammetry (CV) shows apotential window between +0.7 and -0.7 V vs. Ag/AgCl. The voltammetry of ferrocene and7,7,8,8-tetracyanoquinodimethane (TCNQ) indicates that diffusion coefficients are in the range of10^(-8) -10^(-9) cm^2/s. Ionic conductivities are approximately 10^(-6) S/cm. Similar films usingdimethyl sulfoxide (DMSO) as a plasticizer instead of MPEG-400 have demonstrated ionicconductivities of 10^(-4) S/cm and reversible voltammetry. However, UV spectropho-tometry shows that70% of the DMSO is lost under vacuum, indicating the difficulty in quantifying the DMSO contentwhen exposed to vacuum.
