α,α'-Dicinnamoyl ketene cyclic S, S-acetals 4 were reacted with ethylenediamine to afford α,α'-dicinnamoyl ketene cyclic N,N-acetals 5. This process provides a new method for thesynthesis of 5 in high yiel...α,α'-Dicinnamoyl ketene cyclic S, S-acetals 4 were reacted with ethylenediamine to afford α,α'-dicinnamoyl ketene cyclic N,N-acetals 5. This process provides a new method for thesynthesis of 5 in high yield under mild conditions.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
α-Oxoketene dithioacetals( compound 1 ) are versatile synthons for organic synthesis due to their specially structural characteristic, that is, the masked ketene is conjugated with the convertible carbonyl in their...α-Oxoketene dithioacetals( compound 1 ) are versatile synthons for organic synthesis due to their specially structural characteristic, that is, the masked ketene is conjugated with the convertible carbonyl in their molecules. Although there have been numerous reports covering the reactions in which they have been taken as 1,3-electrophiles, the reaction at the α-carbon atom of α-oxoketene dithioacetals has seldom been investigated. Junjappa and co-workers found the α- bromination of compound 2 in the presence of NBS led to α-aroyl-α-bromo ketenedithioacetals. However, the flexibility of the functional groups at the α-carbon atom of compound 2 are still limited.展开更多
Heterocyclic ketene aminals 1 react with aryl azides 2 to give the titled compounds 3,and in some cases also with the formation of fused heterocycles 4.
The title compounds 3 and 4 condensed with aromatic aldehydes to give a--aroylsicinnamoyl ketene cyclic dithioacetals 5 and 6 with sodium ethoxide as the base. The stereochemistryofs and 6 was assigned as E-configurat...The title compounds 3 and 4 condensed with aromatic aldehydes to give a--aroylsicinnamoyl ketene cyclic dithioacetals 5 and 6 with sodium ethoxide as the base. The stereochemistryofs and 6 was assigned as E-configuration by 1H NMR.展开更多
The fused heterocyclic compounds 2 : imidazo [1.2-a] pyriding 2a-c and pyrido [ 1 .2-a] pyrimidine 2d were obtained from the reaction of α-cinnamoyl ketene dibenzylthio acetals 1 with diamine. When α-cinnamoyl -a...The fused heterocyclic compounds 2 : imidazo [1.2-a] pyriding 2a-c and pyrido [ 1 .2-a] pyrimidine 2d were obtained from the reaction of α-cinnamoyl ketene dibenzylthio acetals 1 with diamine. When α-cinnamoyl -a'-benzoyl ketene N. N-acetals 3a-b were treated by t-BuONa/t- BuOH Solution. 8- benzoyl-pyrido[1.2-a] pyrimidine 4 was produced.展开更多
The dihydric dithioketenes 3a-c obtained by 1,2-addition of methallyl Grignard reagent to bis(alkylthio)methylidene derivative ofdimedone 2a-c wewr converted to the cycloaromatization product 4 assisted by boron trifl...The dihydric dithioketenes 3a-c obtained by 1,2-addition of methallyl Grignard reagent to bis(alkylthio)methylidene derivative ofdimedone 2a-c wewr converted to the cycloaromatization product 4 assisted by boron trifluoride etherate.When this reaction was performed in methanol,the substitution-cycloaroatization product 5 was obtained as by- product from 3c.To this eycloaromatization reaction,,the reactivity order dimethylthio>1, 3 - propylenedithio>1, 2- ethylenedithio carbon cation was established by the yields from 3a-c 4.An intramolecular a1,a1reaction pattern was developed by experiment.展开更多
Benzoxazoline ring substituted ketene N,O-acetals 3 were synthesized by the reaction of ketene S,S-acetals 2 with 2-aminophenol.The tautomeric equilibrium of some 3 was also observed.
Polymerization of three cyclic ketene acetals: i.e., 5,6-benzo-2-methylene-1,3-dioxepane (BMDO), 2-methylene-4phenyl-1,3-dioxolane (MPDO) and 4,7-dimethyl-2-methylene-1,3-dioxepane (DMMDO) were carried out in the pres...Polymerization of three cyclic ketene acetals: i.e., 5,6-benzo-2-methylene-1,3-dioxepane (BMDO), 2-methylene-4phenyl-1,3-dioxolane (MPDO) and 4,7-dimethyl-2-methylene-1,3-dioxepane (DMMDO) were carried out in the presence of ethyl alpha -bromobutyrate/CuBr/2,2'-bipyridine respectively. The structures of poly(BMDO), poly(MPDO) and poly(DMMDO) were characterized by H-1 and C-13-NMR spectra. The effects of monomer structure on the behavior of atom transfer free radical ring-opening polymerization were investigated and the mechanism of controlled free radical ring-opening polymerization was discussed.展开更多
The anion of heterocyclic ketene aminals reacted with 2,4-dini- tro-halobenzenes to give an arylated product through the radical nucleo- philic substitution confirmed by ESR spectroscopy,ESR-spin trapping techni- que,...The anion of heterocyclic ketene aminals reacted with 2,4-dini- tro-halobenzenes to give an arylated product through the radical nucleo- philic substitution confirmed by ESR spectroscopy,ESR-spin trapping techni- que,and depression of the reaction rate by the addition of inhibitor.展开更多
Heteroatom aroyl-substituted heterocyclic ketene aminals 1 reacted with 2,3,4,6-tetra-O-acetyl-α-glucopyranosyl bromide 2 under the catalysis of Hg(CN)2 or CaH2 to give E- or Z-O-glycosides of heterocyclic ketene am...Heteroatom aroyl-substituted heterocyclic ketene aminals 1 reacted with 2,3,4,6-tetra-O-acetyl-α-glucopyranosyl bromide 2 under the catalysis of Hg(CN)2 or CaH2 to give E- or Z-O-glycosides of heterocyclic ketene aminals 3 or 4 in moderate yields.展开更多
A new method for the synthesis of substituted thiophenes was through intramolecular aldol condensation ofα-oxo ketene dibenzylthioacetals.All products were confirmed with IR, 1 H NMR and elemental analysis.
The charge density of cellulose fibers is a key parameter in the papermaking systems,and this is particularly true for the Alkyl Ketene Dimer( AKD) paper sizing.Zeta potential and cationic demand are often used to cha...The charge density of cellulose fibers is a key parameter in the papermaking systems,and this is particularly true for the Alkyl Ketene Dimer( AKD) paper sizing.Zeta potential and cationic demand are often used to characterize these charges.Generally,a similar sizing performance would be obtained when the fibers with similar morphology and charge characteristics are used.However,in a mill trial,it was shown that three bleached birch pulp samples,with similar fiber morphology,and zeta potential,had different AKD sizing behaviors.In this study,the surface charges of these pulp samples,measured using the polyelectrolyte titration methods,were investigated.The results showed that lower sizing efficiency of fibers were due to their lower surface charges.It was concluded that the direct measurement of surface charge of cellulose fibers can be more appropriate to evaluate the AKD paper sizing efficiency.展开更多
The cycloaddition reaction of ketene and formaldehyde,lesding to 2- oxetanone,has been studied theoretically by means of RHF/3-21G.This reaction is believed to be nonsynchronous but concerted,taking place through a tw...The cycloaddition reaction of ketene and formaldehyde,lesding to 2- oxetanone,has been studied theoretically by means of RHF/3-21G.This reaction is believed to be nonsynchronous but concerted,taking place through a twisted four membered ring transition state.Two types of frontier orbital interactions are involved in this reaction.The activation barrier is calculated to be 123.1KJ/mol (MP2/3-21G result).展开更多
The cycloaddition reactions between ketene or substituted ketenes and cyelopentadiene have been studied theoretically by means of the semiempirical AMI method.Three different substituted ketenes have been selected and...The cycloaddition reactions between ketene or substituted ketenes and cyelopentadiene have been studied theoretically by means of the semiempirical AMI method.Three different substituted ketenes have been selected and ten transition states,corresponding to different approach geometries have been located and characterized,The regioselectivity and stereoselectivity of the reactions are correctly predicted by the calculations and the reaction mechanisms are analyzed in terms of electronic and steric effects of the substitutents on the reacting ketene and cyc-lopentadiene.展开更多
A facile route to 2-benzylthio-5-phenyl-3,4-disubstituted thiophenes was described. Catalyzed by sodium hydroxide, the title compounds were synthesized in moderate to good yields simply from the intramolecular aldol t...A facile route to 2-benzylthio-5-phenyl-3,4-disubstituted thiophenes was described. Catalyzed by sodium hydroxide, the title compounds were synthesized in moderate to good yields simply from the intramolecular aldol type condensation of α-oxo ketene dibenzylthioacetals. The chemical selectivity for this annulation reaction was studied and discussed.展开更多
A cost-effective and environmentally compliance FeCl3·6H2O catalyzed Friedel-Crafts alkylation of cyclic ketene dithioacetals with alcohols was developed. The reaction was efficient in the presence of catalyst lo...A cost-effective and environmentally compliance FeCl3·6H2O catalyzed Friedel-Crafts alkylation of cyclic ketene dithioacetals with alcohols was developed. The reaction was efficient in the presence of catalyst loading as low as 5%(molar fraction) in CH2Cl2 solvent at room temperature or under reflux conditions. A wide range of alkylated ketene dithioacetals were synthesized in excellent yields.展开更多
A FeCl3-6H2O-catalyzed synthesis of β-ketothioesters from the hydrolysis reaction of chain α-oxoketene dithioacetals was carried out. Subsequently, we explored the FeCl3-6H2O-catalyzed Friedel-Crafts alkylation of t...A FeCl3-6H2O-catalyzed synthesis of β-ketothioesters from the hydrolysis reaction of chain α-oxoketene dithioacetals was carried out. Subsequently, we explored the FeCl3-6H2O-catalyzed Friedel-Crafts alkylation of the synthesized fl-ketothioesters with alcohols in CH3CN at 25 ℃, affording the desired α-alkylated fl-ketothioesters in excellent yields. Wide scope of the substrates, use of inexpensive reagents, high yields under mild reaction conditions are notable features of these reactions.展开更多
文摘α,α'-Dicinnamoyl ketene cyclic S, S-acetals 4 were reacted with ethylenediamine to afford α,α'-dicinnamoyl ketene cyclic N,N-acetals 5. This process provides a new method for thesynthesis of 5 in high yield under mild conditions.
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Supported by the National Natural Science Foundation of China(No. 29862004) Scientific and Technological DevelopmentProgram Foundation of Jilin Province(No. 20040565).
文摘α-Oxoketene dithioacetals( compound 1 ) are versatile synthons for organic synthesis due to their specially structural characteristic, that is, the masked ketene is conjugated with the convertible carbonyl in their molecules. Although there have been numerous reports covering the reactions in which they have been taken as 1,3-electrophiles, the reaction at the α-carbon atom of α-oxoketene dithioacetals has seldom been investigated. Junjappa and co-workers found the α- bromination of compound 2 in the presence of NBS led to α-aroyl-α-bromo ketenedithioacetals. However, the flexibility of the functional groups at the α-carbon atom of compound 2 are still limited.
文摘Heterocyclic ketene aminals 1 react with aryl azides 2 to give the titled compounds 3,and in some cases also with the formation of fused heterocycles 4.
文摘The title compounds 3 and 4 condensed with aromatic aldehydes to give a--aroylsicinnamoyl ketene cyclic dithioacetals 5 and 6 with sodium ethoxide as the base. The stereochemistryofs and 6 was assigned as E-configuration by 1H NMR.
文摘The fused heterocyclic compounds 2 : imidazo [1.2-a] pyriding 2a-c and pyrido [ 1 .2-a] pyrimidine 2d were obtained from the reaction of α-cinnamoyl ketene dibenzylthio acetals 1 with diamine. When α-cinnamoyl -a'-benzoyl ketene N. N-acetals 3a-b were treated by t-BuONa/t- BuOH Solution. 8- benzoyl-pyrido[1.2-a] pyrimidine 4 was produced.
文摘The dihydric dithioketenes 3a-c obtained by 1,2-addition of methallyl Grignard reagent to bis(alkylthio)methylidene derivative ofdimedone 2a-c wewr converted to the cycloaromatization product 4 assisted by boron trifluoride etherate.When this reaction was performed in methanol,the substitution-cycloaroatization product 5 was obtained as by- product from 3c.To this eycloaromatization reaction,,the reactivity order dimethylthio>1, 3 - propylenedithio>1, 2- ethylenedithio carbon cation was established by the yields from 3a-c 4.An intramolecular a1,a1reaction pattern was developed by experiment.
基金This work was supported by the National Natural Science Foundation of China
文摘Benzoxazoline ring substituted ketene N,O-acetals 3 were synthesized by the reaction of ketene S,S-acetals 2 with 2-aminophenol.The tautomeric equilibrium of some 3 was also observed.
基金This work was supported by the National Natural Science Foundation of China (No. 59774027).
文摘Polymerization of three cyclic ketene acetals: i.e., 5,6-benzo-2-methylene-1,3-dioxepane (BMDO), 2-methylene-4phenyl-1,3-dioxolane (MPDO) and 4,7-dimethyl-2-methylene-1,3-dioxepane (DMMDO) were carried out in the presence of ethyl alpha -bromobutyrate/CuBr/2,2'-bipyridine respectively. The structures of poly(BMDO), poly(MPDO) and poly(DMMDO) were characterized by H-1 and C-13-NMR spectra. The effects of monomer structure on the behavior of atom transfer free radical ring-opening polymerization were investigated and the mechanism of controlled free radical ring-opening polymerization was discussed.
文摘The anion of heterocyclic ketene aminals reacted with 2,4-dini- tro-halobenzenes to give an arylated product through the radical nucleo- philic substitution confirmed by ESR spectroscopy,ESR-spin trapping techni- que,and depression of the reaction rate by the addition of inhibitor.
基金This work is supported by the National Natural Science Foundation of China (No. 29972030) and the Research Fund for the Doctoral Program of Higher Education.
文摘Heteroatom aroyl-substituted heterocyclic ketene aminals 1 reacted with 2,3,4,6-tetra-O-acetyl-α-glucopyranosyl bromide 2 under the catalysis of Hg(CN)2 or CaH2 to give E- or Z-O-glycosides of heterocyclic ketene aminals 3 or 4 in moderate yields.
文摘A new method for the synthesis of substituted thiophenes was through intramolecular aldol condensation ofα-oxo ketene dibenzylthioacetals.All products were confirmed with IR, 1 H NMR and elemental analysis.
基金National Natural Science Foundation of China(No.31370578)State Key Laboratory of Pulp and Paper Engineering,China(No.201508)
文摘The charge density of cellulose fibers is a key parameter in the papermaking systems,and this is particularly true for the Alkyl Ketene Dimer( AKD) paper sizing.Zeta potential and cationic demand are often used to characterize these charges.Generally,a similar sizing performance would be obtained when the fibers with similar morphology and charge characteristics are used.However,in a mill trial,it was shown that three bleached birch pulp samples,with similar fiber morphology,and zeta potential,had different AKD sizing behaviors.In this study,the surface charges of these pulp samples,measured using the polyelectrolyte titration methods,were investigated.The results showed that lower sizing efficiency of fibers were due to their lower surface charges.It was concluded that the direct measurement of surface charge of cellulose fibers can be more appropriate to evaluate the AKD paper sizing efficiency.
基金This project is supported by Foundation of National Education Committee and Natural Science Fund of China
文摘The cycloaddition reaction of ketene and formaldehyde,lesding to 2- oxetanone,has been studied theoretically by means of RHF/3-21G.This reaction is believed to be nonsynchronous but concerted,taking place through a twisted four membered ring transition state.Two types of frontier orbital interactions are involved in this reaction.The activation barrier is calculated to be 123.1KJ/mol (MP2/3-21G result).
文摘The cycloaddition reactions between ketene or substituted ketenes and cyelopentadiene have been studied theoretically by means of the semiempirical AMI method.Three different substituted ketenes have been selected and ten transition states,corresponding to different approach geometries have been located and characterized,The regioselectivity and stereoselectivity of the reactions are correctly predicted by the calculations and the reaction mechanisms are analyzed in terms of electronic and steric effects of the substitutents on the reacting ketene and cyc-lopentadiene.
文摘A facile route to 2-benzylthio-5-phenyl-3,4-disubstituted thiophenes was described. Catalyzed by sodium hydroxide, the title compounds were synthesized in moderate to good yields simply from the intramolecular aldol type condensation of α-oxo ketene dibenzylthioacetals. The chemical selectivity for this annulation reaction was studied and discussed.
基金Supported by the National Natural Science Foundation of China(No,20902010), the Foundation of Liaoning Provincial Education Administration, China(No.L2015003) and the Science Foundation of Anshan City, China(Nos.2012KJ02, 2014KJ05).
文摘A cost-effective and environmentally compliance FeCl3·6H2O catalyzed Friedel-Crafts alkylation of cyclic ketene dithioacetals with alcohols was developed. The reaction was efficient in the presence of catalyst loading as low as 5%(molar fraction) in CH2Cl2 solvent at room temperature or under reflux conditions. A wide range of alkylated ketene dithioacetals were synthesized in excellent yields.
基金Supported by the Fundamental Research Funds for the Jilin Province Key Laboratory of Organic Functional Molecular Design & Synthesis, China(No.130028652), the Natural Science Foundation of Liaoning Province, China(No.201602002), the Foundation of Liaoning Province Education Administration, China(No.L2015003) and the National Natural Science Foundation of China(No.20902010).
文摘A FeCl3-6H2O-catalyzed synthesis of β-ketothioesters from the hydrolysis reaction of chain α-oxoketene dithioacetals was carried out. Subsequently, we explored the FeCl3-6H2O-catalyzed Friedel-Crafts alkylation of the synthesized fl-ketothioesters with alcohols in CH3CN at 25 ℃, affording the desired α-alkylated fl-ketothioesters in excellent yields. Wide scope of the substrates, use of inexpensive reagents, high yields under mild reaction conditions are notable features of these reactions.