New chiral C_2-symmetrical bis(oxazoline) compounds bearing one isobutyl-, secbutyl-, benzyl- or isopropyl-substituent at the 4-position have been prepared and characterized.
The synthesis of bis(oxazoline) dicarboxylate derivatives was investigated. Diethyl-aminosulfur trifluoride (DAST) was used as a convenient cyclization reagent in the synthesis of bis(oxazoline) dicarboxylate derivati...The synthesis of bis(oxazoline) dicarboxylate derivatives was investigated. Diethyl-aminosulfur trifluoride (DAST) was used as a convenient cyclization reagent in the synthesis of bis(oxazoline) dicarboxylate derivatives, which can not be obtained by the general method using MsCl and Et3N as dehydrating cyclization reagent.展开更多
The electronic effect of diphenylamine-linked bis(oxazoline) ligands was tuned through introduction of electron-withdrawing bromo and nitro substituents onto the 4 and 4′ position. The variation of the NH bond acidit...The electronic effect of diphenylamine-linked bis(oxazoline) ligands was tuned through introduction of electron-withdrawing bromo and nitro substituents onto the 4 and 4′ position. The variation of the NH bond acidity was determined by the different chemical shifts of NH. The catalytic activity and enantioselectivity of the modified ligands were tested in the asymmetric Friedel-Crafts alkylation of indole with β-nitrostyrene. The effect of ligand skeleton rigidity was also investigated through the synthesis of iminodibenzyl-linked bis(oxazoline) ligands and evaluation of their catalytic activity in Friedel-Crafts alkylation.展开更多
A series of novel chiral C 2 symmetric bis(oxazoline) ligands have been synthesized. The copper and magnesium complexes, prepared in situ from copper(II) triflate or magnesium triflate with the new enantiop...A series of novel chiral C 2 symmetric bis(oxazoline) ligands have been synthesized. The copper and magnesium complexes, prepared in situ from copper(II) triflate or magnesium triflate with the new enantiopure oxazoline ligands, were evaluated as chiral catalysts in the enantioselective Diels Alder reaction of cyclopentadiene with N crotenoyl oxazolidin 2 one. Primary results showed that diastereoselectivity up to 94% and enantioselectivity up to 68% ee for endo products were observed respectively with these ligands.展开更多
The mass spectrometric fragmentation of 1,8-bis [ 4-substituted （oxazolin-2-yl） ] anthracenes （AnBOXes） was investigated by using mass-analyzed ion kinetic energy spectrometry under electron-impact ionization cond...The mass spectrometric fragmentation of 1,8-bis [ 4-substituted （oxazolin-2-yl） ] anthracenes （AnBOXes） was investigated by using mass-analyzed ion kinetic energy spectrometry under electron-impact ionization conditions. All the compounds could undergo a ring contraction by the loss of an RCH = CH2 molecule to form 1-oxazirinyl-8-（oxazolin- 2-yl） anthracene ions, which could further lose an R radical, followed by the loss of oxazoline. These ions could also eliminate an R radical and subsequently undergo ring-contraction rearrangements to lose a CHCH2O fragraent and an epoxide molecule, respectively. The ions that are formed could further lose CHCH2O and CH2 = CH fragments. Several ring-contraction rearrangements of the oxazoline ring were observed under electron-impact ionization conditions.展开更多
The condensation of 4-bromobenzaldehyde with 2-ethoxycarbonyl-3,4-dimethylpyrrole gave Compound 3,which after hydrolyzation,was converted to the corresponding diacid 4.Six bis(oxazoline)compounds were synthesized dire...The condensation of 4-bromobenzaldehyde with 2-ethoxycarbonyl-3,4-dimethylpyrrole gave Compound 3,which after hydrolyzation,was converted to the corresponding diacid 4.Six bis(oxazoline)compounds were synthesized directly by the diacid reacting with chiral aminoalcohols.展开更多
基金the Foundation for Academic Leader by the Education Department of Hunan province.
文摘New chiral C_2-symmetrical bis(oxazoline) compounds bearing one isobutyl-, secbutyl-, benzyl- or isopropyl-substituent at the 4-position have been prepared and characterized.
文摘The synthesis of bis(oxazoline) dicarboxylate derivatives was investigated. Diethyl-aminosulfur trifluoride (DAST) was used as a convenient cyclization reagent in the synthesis of bis(oxazoline) dicarboxylate derivatives, which can not be obtained by the general method using MsCl and Et3N as dehydrating cyclization reagent.
基金Supported by the National Natural Science Foundation of China (Grant No. 20772006)the Program for New Century Excellent Talents in University (Grant No. NCET-07-0011)the Development Program for Distinguished Mid-Youth Teachers of Beijing Institute of Technology
文摘The electronic effect of diphenylamine-linked bis(oxazoline) ligands was tuned through introduction of electron-withdrawing bromo and nitro substituents onto the 4 and 4′ position. The variation of the NH bond acidity was determined by the different chemical shifts of NH. The catalytic activity and enantioselectivity of the modified ligands were tested in the asymmetric Friedel-Crafts alkylation of indole with β-nitrostyrene. The effect of ligand skeleton rigidity was also investigated through the synthesis of iminodibenzyl-linked bis(oxazoline) ligands and evaluation of their catalytic activity in Friedel-Crafts alkylation.
文摘A series of novel chiral C 2 symmetric bis(oxazoline) ligands have been synthesized. The copper and magnesium complexes, prepared in situ from copper(II) triflate or magnesium triflate with the new enantiopure oxazoline ligands, were evaluated as chiral catalysts in the enantioselective Diels Alder reaction of cyclopentadiene with N crotenoyl oxazolidin 2 one. Primary results showed that diastereoselectivity up to 94% and enantioselectivity up to 68% ee for endo products were observed respectively with these ligands.
基金Supported by the National Natural Science Foundation of China(No. 20272002).
文摘The mass spectrometric fragmentation of 1,8-bis [ 4-substituted （oxazolin-2-yl） ] anthracenes （AnBOXes） was investigated by using mass-analyzed ion kinetic energy spectrometry under electron-impact ionization conditions. All the compounds could undergo a ring contraction by the loss of an RCH = CH2 molecule to form 1-oxazirinyl-8-（oxazolin- 2-yl） anthracene ions, which could further lose an R radical, followed by the loss of oxazoline. These ions could also eliminate an R radical and subsequently undergo ring-contraction rearrangements to lose a CHCH2O fragraent and an epoxide molecule, respectively. The ions that are formed could further lose CHCH2O and CH2 = CH fragments. Several ring-contraction rearrangements of the oxazoline ring were observed under electron-impact ionization conditions.
文摘The condensation of 4-bromobenzaldehyde with 2-ethoxycarbonyl-3,4-dimethylpyrrole gave Compound 3,which after hydrolyzation,was converted to the corresponding diacid 4.Six bis(oxazoline)compounds were synthesized directly by the diacid reacting with chiral aminoalcohols.
