Four chiral 1,1?bis(oxazolinyl)ferrocenes(1a-1d) have been prepared and used as ligands in the copper catalyzed asymmetric cyclopropanation of styrene with ethyl diazoacetate (EDA) and the magnesium catalyzed Diels-Al...Four chiral 1,1?bis(oxazolinyl)ferrocenes(1a-1d) have been prepared and used as ligands in the copper catalyzed asymmetric cyclopropanation of styrene with ethyl diazoacetate (EDA) and the magnesium catalyzed Diels-Alder reaction between 3-acryloyl-2-oxazolidinone and cyclopentadiene. Enantioselectivities up to 24% and 41%, respectively, for cyclopropanation and Diels-Alder reaction were observed.展开更多
The mechanism, catalytic effect and substituent effect of the hetero-Diels-Alder reactions between phosphonodithioformate and butadienes have been investigated theoretically using density functional theory at the B3LY...The mechanism, catalytic effect and substituent effect of the hetero-Diels-Alder reactions between phosphonodithioformate and butadienes have been investigated theoretically using density functional theory at the B3LYP/6-31G（d） level. The results show that all of these reactions proceed in a concerted but asynchronous way. In some reactions the formation of C-S bond is prior to that of C-C and opposite result is found in other reactions. The BF3 catalyst and trimethylsilyloxy group may lower the activation barriers by changing the energies of FMOs for reactant molecules. With the BF3-catalyzed reactions, the complete regioselectivity observed experimentally has well been reproduced by theoretical calculation and these results originate probably from blue-shifting C-H...F hydrogen bond interaction in some transition states.展开更多
The stereoselectivity of some Diels-Alder reactions was investigated by means of ABEEM-oTr model. Combined with local hard-soft and acid-base （HSAB） principle, we made reasonable explanation by calculating local sof...The stereoselectivity of some Diels-Alder reactions was investigated by means of ABEEM-oTr model. Combined with local hard-soft and acid-base （HSAB） principle, we made reasonable explanation by calculating local softness of atom and bond regions for the stereoselectivity of four Diels-Alder reactions involving cyclopentadiene.展开更多
Quinazoline derivatives were synthesized fromα-iminoesters via a cascade imino-Diels-Alder and then oxidation reaction catalyzed with CuBr_2.This method provided a new strategy for preparing quinazoline derivatives w...Quinazoline derivatives were synthesized fromα-iminoesters via a cascade imino-Diels-Alder and then oxidation reaction catalyzed with CuBr_2.This method provided a new strategy for preparing quinazoline derivatives which may be useful in the synthesis of heterocyclic intermediates.展开更多
The authors have studied the Diels-Alder reactions between furan derivatives and maleimide derivatives in an ionic liquid and have found that higher reactivity can be obtained in a protic ionic liquid [Mim]Tf2N than i...The authors have studied the Diels-Alder reactions between furan derivatives and maleimide derivatives in an ionic liquid and have found that higher reactivity can be obtained in a protic ionic liquid [Mim]Tf2N than in the conventional organic solvent. Furthermore, in the Diels-Alder reactions of 2- and 2,5-alkylfurans with N-alkylma- leimide, the reactivity increases by extending the alkyl chain length of N-alkylmaleimide. In addition, it was demon- strated that endo-selectivity increases when 2,5-disubstituted furans are used. These results will be explained by comparing the stability of the Diels-Alder adduct with that of the products obtained from the reactions of 2-substituted furans and 2,5-disubstituted furans.展开更多
Four novel bisoxazoline ligands 8a-d were synthesized from （S）-amino alcohols and could be formed effective catalysts （up to 77% ee for endo isomer） with Cu（OTf）2 for enantioselective Diels-Alder addition. The f...Four novel bisoxazoline ligands 8a-d were synthesized from （S）-amino alcohols and could be formed effective catalysts （up to 77% ee for endo isomer） with Cu（OTf）2 for enantioselective Diels-Alder addition. The facility of the reaction was dependent on the nature of the substituent R in the bisoxazoline ligand.展开更多
Diels-Alder reaction of hedychenone 1 and maleic anhydride 2 gave several products 4 similar to 7, whose structures were identified by spectral methods. Effect of temperature on the reaction was disscussed.
The mechanism, catalytic effect and solvent effect of the hetero-Diels-Alder reactions between 3-pyddinedithioesters and 1-phenylsulfanylbutadiene have been studied theoretically using density functional theory （DFT...The mechanism, catalytic effect and solvent effect of the hetero-Diels-Alder reactions between 3-pyddinedithioesters and 1-phenylsulfanylbutadiene have been studied theoretically using density functional theory （DFT） at the B3LYP/6-31G（d） level. The results show that all of these reactions proceed in a concerted but asynchronous way. In some reactions the formation of C-S bond is prior to that of C-C bond and the opposite results are found in other reactions. The BF3 catalyst may lower the activation barriers by changing the energies of LUMO for 3-pyridinedithioester. THF solvent has trivial influence on the potential energy surface of these reactions. With the BF3-catalyzed reactions, regioselectivity and stereoselectivity observed experimentally were predicted correctly by calculations and these results originate probably from C-H…F interaction in two transition states.展开更多
Novel Schiff bases of H4＇-NOBIN 5a and 5b were synthesized by condensation of 3 with aldehydes. Compound 5b was structurally characterized by single-crystal X-ray diffraction. The asymmetric hetero-Diels-Alder reacti...Novel Schiff bases of H4＇-NOBIN 5a and 5b were synthesized by condensation of 3 with aldehydes. Compound 5b was structurally characterized by single-crystal X-ray diffraction. The asymmetric hetero-Diels-Alder reactions were carried out with high yields and good enantioselectivities in the presence of Ti-（S）-5a complex as catalyst. Crystallographic data for 5b： C27H22BrNO, Mr = 456.37, triclinic, space group P1 with a = 9.1618（2）, b = 10.3836（2）, c = 12.7718（2） А,α=105.4860（10）,β= 94.6360（10）, γ= 108.4610（10）°, V= 1092.32（4）А^3, Z=2, Dc= 1.388 g/cm^3, μ= 1.900 mm^-1, F（000） = 468, R = 0.0476 and wR = 0.1248 for 3092 observed reflections （I〉 2σ（I））.展开更多
Aluminum chloride induced Diels-Alder reactions of 3-carboethoxy- and 3-carbonitrile-2-cyclohexen-1-one with cyclopentadiene, isoprene and (E)-piperylene were described. Thestereochemistry of the adducts were confirme...Aluminum chloride induced Diels-Alder reactions of 3-carboethoxy- and 3-carbonitrile-2-cyclohexen-1-one with cyclopentadiene, isoprene and (E)-piperylene were described. Thestereochemistry of the adducts were confirmed by 2D-NMR spectroscopy and isomerizationreactions.展开更多
文摘Four chiral 1,1?bis(oxazolinyl)ferrocenes(1a-1d) have been prepared and used as ligands in the copper catalyzed asymmetric cyclopropanation of styrene with ethyl diazoacetate (EDA) and the magnesium catalyzed Diels-Alder reaction between 3-acryloyl-2-oxazolidinone and cyclopentadiene. Enantioselectivities up to 24% and 41%, respectively, for cyclopropanation and Diels-Alder reaction were observed.
文摘The mechanism, catalytic effect and substituent effect of the hetero-Diels-Alder reactions between phosphonodithioformate and butadienes have been investigated theoretically using density functional theory at the B3LYP/6-31G（d） level. The results show that all of these reactions proceed in a concerted but asynchronous way. In some reactions the formation of C-S bond is prior to that of C-C and opposite result is found in other reactions. The BF3 catalyst and trimethylsilyloxy group may lower the activation barriers by changing the energies of FMOs for reactant molecules. With the BF3-catalyzed reactions, the complete regioselectivity observed experimentally has well been reproduced by theoretical calculation and these results originate probably from blue-shifting C-H...F hydrogen bond interaction in some transition states.
基金the grants from the National Natural Science Foundation of China.(No.20633050 and 20403007).
文摘The stereoselectivity of some Diels-Alder reactions was investigated by means of ABEEM-oTr model. Combined with local hard-soft and acid-base （HSAB） principle, we made reasonable explanation by calculating local softness of atom and bond regions for the stereoselectivity of four Diels-Alder reactions involving cyclopentadiene.
基金the financial support from National Natural Science Foundation of China(No.20972198).
文摘Quinazoline derivatives were synthesized fromα-iminoesters via a cascade imino-Diels-Alder and then oxidation reaction catalyzed with CuBr_2.This method provided a new strategy for preparing quinazoline derivatives which may be useful in the synthesis of heterocyclic intermediates.
文摘The authors have studied the Diels-Alder reactions between furan derivatives and maleimide derivatives in an ionic liquid and have found that higher reactivity can be obtained in a protic ionic liquid [Mim]Tf2N than in the conventional organic solvent. Furthermore, in the Diels-Alder reactions of 2- and 2,5-alkylfurans with N-alkylma- leimide, the reactivity increases by extending the alkyl chain length of N-alkylmaleimide. In addition, it was demon- strated that endo-selectivity increases when 2,5-disubstituted furans are used. These results will be explained by comparing the stability of the Diels-Alder adduct with that of the products obtained from the reactions of 2-substituted furans and 2,5-disubstituted furans.
基金Finacial support by the National Natural Science Foundation of China(No.2047211)the Science Foundation of China Agricultural University(No.2005058)is gratefully acknowledged.
文摘Four novel bisoxazoline ligands 8a-d were synthesized from （S）-amino alcohols and could be formed effective catalysts （up to 77% ee for endo isomer） with Cu（OTf）2 for enantioselective Diels-Alder addition. The facility of the reaction was dependent on the nature of the substituent R in the bisoxazoline ligand.
文摘Diels-Alder reaction of hedychenone 1 and maleic anhydride 2 gave several products 4 similar to 7, whose structures were identified by spectral methods. Effect of temperature on the reaction was disscussed.
文摘The mechanism, catalytic effect and solvent effect of the hetero-Diels-Alder reactions between 3-pyddinedithioesters and 1-phenylsulfanylbutadiene have been studied theoretically using density functional theory （DFT） at the B3LYP/6-31G（d） level. The results show that all of these reactions proceed in a concerted but asynchronous way. In some reactions the formation of C-S bond is prior to that of C-C bond and the opposite results are found in other reactions. The BF3 catalyst may lower the activation barriers by changing the energies of LUMO for 3-pyridinedithioester. THF solvent has trivial influence on the potential energy surface of these reactions. With the BF3-catalyzed reactions, regioselectivity and stereoselectivity observed experimentally were predicted correctly by calculations and these results originate probably from C-H…F interaction in two transition states.
基金supported by the Natural Science Foundation of Zhejiang Province (No. Y405013)
文摘Novel Schiff bases of H4＇-NOBIN 5a and 5b were synthesized by condensation of 3 with aldehydes. Compound 5b was structurally characterized by single-crystal X-ray diffraction. The asymmetric hetero-Diels-Alder reactions were carried out with high yields and good enantioselectivities in the presence of Ti-（S）-5a complex as catalyst. Crystallographic data for 5b： C27H22BrNO, Mr = 456.37, triclinic, space group P1 with a = 9.1618（2）, b = 10.3836（2）, c = 12.7718（2） А,α=105.4860（10）,β= 94.6360（10）, γ= 108.4610（10）°, V= 1092.32（4）А^3, Z=2, Dc= 1.388 g/cm^3, μ= 1.900 mm^-1, F（000） = 468, R = 0.0476 and wR = 0.1248 for 3092 observed reflections （I〉 2σ（I））.
文摘Aluminum chloride induced Diels-Alder reactions of 3-carboethoxy- and 3-carbonitrile-2-cyclohexen-1-one with cyclopentadiene, isoprene and (E)-piperylene were described. Thestereochemistry of the adducts were confirmed by 2D-NMR spectroscopy and isomerizationreactions.
