Efficient Transamination under Mild Conditions: Preparation of Primary Amine Derivatives from Carbonyl Compounds via Imine Isomerization with Catalytic Amounts of Potassium tert-Butoxide
摘要:
1,3-Prototropic rearrangement of N-diphenylmethanimines was successfully performed with a catalytic amount of potassium tert-butoxide. This procedure can also be used with aliphatic and aromatic aldimines and was extended to the isomerization of (1R)-camphorquinone monoimine and N-(4-methoxyphenyl)-4-phenyl-3-iminoazetidin-2-one. The isomerized imines were easily hydrolyzed and isolated as Cbz derivatives.
Described herein are compounds of formula (I), related compositions, and their use, for example in the formation of α-amino acids or a precursor thereof such as an α-aminonitrile.
An Efficient Synthesis of (−)-Chloramphenicol via Asymmetric Catalytic Aziridination: A Comparison of Catalysts Prepared from Triphenylborate and Various Linear and Vaulted Biaryls
作者:Catherine Loncaric、William D. Wulff
DOI:10.1021/ol010180x
日期:2001.11.1
[GRAPHICS]The antibiotic (-)-choramphenicol has been synthesized in only four steps from p-nitro-benzaldehyde in optically pure form from an asymmetric catalytic aziridination reaction with a chiral catalyst prepared from triphenylborate and the (R)-VAPOL ligand. Catalysts generated from the VAPOL and VANOL ligands give much higher asymmetric induction than do catalysts prepared from 6,6'-diphenylVAPOL, BINOL, and BANOL ligands.
Catalytic Asymmetric Synthesis of .alpha.-Amino Phosphonates Using Lanthanoid-Potassium-BINOL Complexes
Regulation of Orthogonal Functions in a Dual Catalyst System. Subservient Role of a Nonchiral Lewis Acid in an Asymmetric Catalytic Heteroatom Diels−Alder Reaction
作者:Cory A. Newman、Jon C. Antilla、Pei Chen、Alexander V. Predeus、Lee Fielding、William D. Wulff
DOI:10.1021/ja069019d
日期:2007.6.13
A catalytic asymmetric heteroatom Diels-Alder reaction of unactivated imines with Danishefsky's diene is described which gives high asymmetric induction for N-benzhydryl imines derived from a variety of aldehydes. The catalyst is derived from B(OPh)(3) and the VAPOL ligand and gives good induction, but the reaction stalls and does not give high conversion (similar to 50%). It was found that in the presence of both the chiral catalyst and excess amounts of B(OPh)(3) the reaction proceeds to completion and gives high yields of the dihydropiperidinone product. Despite the presence of large quantities of the nonchiral Lewis acid B(OPh)(3), the asymmetric induction of the product remains constant (90% ee) as the amount of B(OPh)(3) is steadily increased and does not drop off until the ratio of B(OPh)(3) to VAPOL is 100:1 (82% ee). These observations are interpreted as involving highly separated and different activities for the chiral and nonchiral Lewis acids present in the reaction. Specifically, the excess B(OPh)(3) serves to bind to the product and release the chiral catalyst to turnover more starting material. The B(OPh)(3) does not compete in turning over the starting material, and a series of binding studies reveal that this is likely due to a combination of two factors. The binding studies reveal that the chiral catalyst binds to the starting imine 7 times more strongly than does B(OPh)(3). However, in order to explain the constant asymmetric induction observed despite the addition of increasing amounts of B(OPh)(3), the rate of the reaction of the imine complexed with the chiral catalyst must be at least 10 times faster than the reaction of the imine complexed with B(OPh)(3). Finally, a catalyst generated from BINOL and B(OPh)(3) does not show this phenomenon.