The selectivities, including peri-, regio-, and diastereoselectivities, in the Staudinger reaction involving vicinal diimines and ketenes were investigated theoretically via the density functional theory (DFT) calcu...The selectivities, including peri-, regio-, and diastereoselectivities, in the Staudinger reaction involving vicinal diimines and ketenes were investigated theoretically via the density functional theory (DFT) calculation. The results indicate that vicinal diimines prefer stepwise [2+2] cycloaddition rather than [2+4] cycloaddition to generate cis-4-imino-β-lactams. The diimines attack the less sterically hindered exo-side of ketenes to generate zwitterionic intermediates, which directly undergo a conrota- tory ring closure to produce cis-4-imino-β-lactams whatever diimines with less or more bulky N-substituents. For unsymmetric vicinal ketoaldehyde-derived diimines, their ketimines attack the exo-side of ketenes and undergo a conrotatory ring closure to produce cis-4-aldimino-β-lactams due to less steric effect. The current theoretical studies provide very important information for in-depth understanding of the selective formation of mono-cis-β-lactams from vicinal diimines and ketenes.展开更多
A series of trans-3-chloro-β-lactams was synthesized stereospecifically from imines and chloroacetyl chloride or a mixture of chloroacetyl chloride and nitroacetyl chloride, prepared from vinylidene chloride and a mi...A series of trans-3-chloro-β-lactams was synthesized stereospecifically from imines and chloroacetyl chloride or a mixture of chloroacetyl chloride and nitroacetyl chloride, prepared from vinylidene chloride and a mixture of concentrated nitric acid and sulfuric acid, in the presence of triethylamine. The reaction of vinylidene chloride and the mixed acid was investigated. The formation mechanism of chloroacetyl chloride and nitroacetyl chloride and their reaction process with imines were proposed.展开更多
Syntheses of 4 novel chiral azetidin 2 one derivatives, which were characterized by 1H NMR, IR, specific rotation and elemental analysis, through Staudinger cycloaddition reaction of Schiff base of benzaldehyd...Syntheses of 4 novel chiral azetidin 2 one derivatives, which were characterized by 1H NMR, IR, specific rotation and elemental analysis, through Staudinger cycloaddition reaction of Schiff base of benzaldehyde with chlorine substitution at different position in benzene ring, were described. For the first time, this type of 3 S ,4 R configuration azetidin 2 one mono^crystals with many chiral centers [(3 S ,4 R ) 3 hydroxy N [( S ) (1 phenyl)ethyl ] 4 (2′ chlorophenyl) azetidin 2 one mono^crystal] were obtained, the structures of which were determined by X ray dif fraction analysis. The effects of Schiff base of benzaldehyde with chlorine subs titu tion at different position in benzene ring on stereoselectivity of Staudinger cy cloaddition reaction products were discussed and the results are showed as below : 2 chlorophenyl Schiff base favored to yield 3 S ,4 R configuration prod uct, but 4 chlorophenyl Schiff base favored to yield 3 R ,4 S configuration produc t. The re action orientation of 2,4 dichlorophenyl Schiff base was determined by corporat e effect of 2 and 4 chlorine, and that of the 4 chlorine was more obvious. In co ntrast to 4 chlorophenyl, although the main product was 3 R ,4 S configur ation, 3 chlorophenyl owned lower selectivity.展开更多
文摘The selectivities, including peri-, regio-, and diastereoselectivities, in the Staudinger reaction involving vicinal diimines and ketenes were investigated theoretically via the density functional theory (DFT) calculation. The results indicate that vicinal diimines prefer stepwise [2+2] cycloaddition rather than [2+4] cycloaddition to generate cis-4-imino-β-lactams. The diimines attack the less sterically hindered exo-side of ketenes to generate zwitterionic intermediates, which directly undergo a conrota- tory ring closure to produce cis-4-imino-β-lactams whatever diimines with less or more bulky N-substituents. For unsymmetric vicinal ketoaldehyde-derived diimines, their ketimines attack the exo-side of ketenes and undergo a conrotatory ring closure to produce cis-4-aldimino-β-lactams due to less steric effect. The current theoretical studies provide very important information for in-depth understanding of the selective formation of mono-cis-β-lactams from vicinal diimines and ketenes.
基金Supported by the National Natural Science Foundation of China(Nos.20772005,20972013)the Beijing Natural Science Foundation,China(No.2092022)the Specialized Research Fund for the Doctoral Program of Higher Education,Ministry of Education of China
文摘A series of trans-3-chloro-β-lactams was synthesized stereospecifically from imines and chloroacetyl chloride or a mixture of chloroacetyl chloride and nitroacetyl chloride, prepared from vinylidene chloride and a mixture of concentrated nitric acid and sulfuric acid, in the presence of triethylamine. The reaction of vinylidene chloride and the mixed acid was investigated. The formation mechanism of chloroacetyl chloride and nitroacetyl chloride and their reaction process with imines were proposed.
基金ProjectsupportedbytheNationalNaturalScienceofChina (No .2 0 1710 0 8)
文摘Syntheses of 4 novel chiral azetidin 2 one derivatives, which were characterized by 1H NMR, IR, specific rotation and elemental analysis, through Staudinger cycloaddition reaction of Schiff base of benzaldehyde with chlorine substitution at different position in benzene ring, were described. For the first time, this type of 3 S ,4 R configuration azetidin 2 one mono^crystals with many chiral centers [(3 S ,4 R ) 3 hydroxy N [( S ) (1 phenyl)ethyl ] 4 (2′ chlorophenyl) azetidin 2 one mono^crystal] were obtained, the structures of which were determined by X ray dif fraction analysis. The effects of Schiff base of benzaldehyde with chlorine subs titu tion at different position in benzene ring on stereoselectivity of Staudinger cy cloaddition reaction products were discussed and the results are showed as below : 2 chlorophenyl Schiff base favored to yield 3 S ,4 R configuration prod uct, but 4 chlorophenyl Schiff base favored to yield 3 R ,4 S configuration produc t. The re action orientation of 2,4 dichlorophenyl Schiff base was determined by corporat e effect of 2 and 4 chlorine, and that of the 4 chlorine was more obvious. In co ntrast to 4 chlorophenyl, although the main product was 3 R ,4 S configur ation, 3 chlorophenyl owned lower selectivity.