A new C 2 symmetric chiral Schiff base compound A with relatively flexible chiral environment was synthesized from L (+) tartaric acid. Its structure was determined by NMR, IR, MS etc, and its preponderant conformatio...A new C 2 symmetric chiral Schiff base compound A with relatively flexible chiral environment was synthesized from L (+) tartaric acid. Its structure was determined by NMR, IR, MS etc, and its preponderant conformation was modeled by CS Chem 3D Program. The results showed that its structure is not in a plane and has a big chiral cavity. It was showed that the complex B has different catalytic performance in asymmetric cyclopropanation of styrene and DMHD (2,5 dimethyl 2,4 hexadiene) with diazoacetate. The catalytic mechanism was also discussed.展开更多
Four stereoisomers of a copper-(Schiff-base) complex with double chiral centers were applied to catalyze the asymmetric cyclopropanation. Two of the stereoisomers were also efficient catalysts affording high enantiom...Four stereoisomers of a copper-(Schiff-base) complex with double chiral centers were applied to catalyze the asymmetric cyclopropanation. Two of the stereoisomers were also efficient catalysts affording high enantiomeric excess of up to 91.8%. A mechanism that predicts the observed results accurately was proposed.展开更多
A new chiral β-diketone Cu (Ⅱ) catalyst was synthesized and used for the asymmetric cyclopropanation of styrene with diazoester. A high optical yield (~90%) was achieved. The effect of the structure of substrate on ...A new chiral β-diketone Cu (Ⅱ) catalyst was synthesized and used for the asymmetric cyclopropanation of styrene with diazoester. A high optical yield (~90%) was achieved. The effect of the structure of substrate on the enantioselectivity was studied. Both chendcal yield and optical yield being reduced when the steric bulky substrate was employed. The reaction mechanism and the chiral model of the transition state are under fufther investigation.展开更多
文摘A new C 2 symmetric chiral Schiff base compound A with relatively flexible chiral environment was synthesized from L (+) tartaric acid. Its structure was determined by NMR, IR, MS etc, and its preponderant conformation was modeled by CS Chem 3D Program. The results showed that its structure is not in a plane and has a big chiral cavity. It was showed that the complex B has different catalytic performance in asymmetric cyclopropanation of styrene and DMHD (2,5 dimethyl 2,4 hexadiene) with diazoacetate. The catalytic mechanism was also discussed.
文摘Four stereoisomers of a copper-(Schiff-base) complex with double chiral centers were applied to catalyze the asymmetric cyclopropanation. Two of the stereoisomers were also efficient catalysts affording high enantiomeric excess of up to 91.8%. A mechanism that predicts the observed results accurately was proposed.
文摘A new chiral β-diketone Cu (Ⅱ) catalyst was synthesized and used for the asymmetric cyclopropanation of styrene with diazoester. A high optical yield (~90%) was achieved. The effect of the structure of substrate on the enantioselectivity was studied. Both chendcal yield and optical yield being reduced when the steric bulky substrate was employed. The reaction mechanism and the chiral model of the transition state are under fufther investigation.
