Asymmetric synthesis of 1-substituted-1-(pyridin-2-yl)methylamines by diastereoselective reduction of enantiopure N-p-toluenesulfinyl ketimines

Reduction of enantiopure N-p-toluenesulfinyl ketimines derived from 2-pyridyl ketones affords N-p-toluenesulfinyl amines with good yields and diastereoselectivities.     

CHIRAL VARIANTS OF ARYLALKYL SULFUR REAGENTS. (R)-CAMPHOR KETIMINES OF OGIOVANNA AMINOTHIOETHERS AND OXIDES

Abstract

Ketimines la-d derived from ortho-aminosubstituted phenylthioethers were prepared in order to determine the degree of chirality transfer from the chiral auxiliary to the sulfur atom in the formation of the sulfoxide or to the α-carbon atom in the reaction of the anion with alkyl halides or benzaldehyde. Oxidation to the sulfoxide occurred with little or no asymmetric induction. The crystalline benzyl sulfone 4c was deprotonated by alkyllithium or Grignard reagents and reacted with alkyl halides and benzaldehyde, in all cases with little to fair transfer of chirality. The major diastereoisomer from methylation of the anion of 4c with methyl iodide, was isolated, and afforded the enantiomerically pure amine 5 after removal of the chiral auxiliary. An X-ray structure determination of 4d allowed the assignment of the absolute configuration of the asymmetric carbon and revealed that the conformation of the ketimine in the crystal state is not homogeneous.     

Asymmetric phase-transfer catalysts bearing multiple hydrogen-bonding donors: Synthesis and application in nitro-Mannich reaction of isatin-derived N-Boc ketimines

A series of bifunctional asymmetric phase-transfer catalysts bearing multiple hydrogen-bonding donors derived from cinchona alkaloids are synthesized, and successfully applied to asymmetric nitro-Mannich of isatin-derived N-Boc ketimines. The products 3-substituted 3-amino-oxindoles were constructed in excellent yields (96–99%) and good enantioselectivities (up to 95% ee).     

Highly Diastereoselective Synthesis of α‐Difluoromethyl Amines from N‐tert‐Butylsulfinyl Ketimines and Difluoromethyl Phenyl Sulfone

The first highly efficient and stereoselective difluoromethylation of structurally diverse N‐tert‐butylsulfinyl ketimines has been achieved with an in situ generated PhSO₂CF₂^? anion, which provides a powerful synthetic method for the preparation of a variety of structurally diverse homochiral α‐difluoromethyl tertiary carbinamines, including α‐difluoromethyl allylic amines and α‐difluoromethyl propargylamines. The stereocontrol mode of the present diastereoselective difluoromethylation of ketimines was found to be different from that of other known fluoroalkylations of N‐tert‐butylsulfinyl aldimines, which suggests that a cyclic six‐membered transition state may be involved in the reaction.     

Synthesis and some properties of phosphorus-substituted azomethines

A series of phosphorus(iii)-substituted azomethines and enamines were synthesized by the reaction of lithium salts of aldimines and ketimines with derivatives of phosphorus(iii) acids. Some properties of the compounds synthesized were studied. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 339–346, February, 1998.     

Phosphine‐mediated Highly Enantioselective Spirocyclization with Ketimines as Substrates

Phosphine‐catalyzed enantioselective annulation reactions involving ketimines are a daunting synthetic challenge owing to the intrinsic low reactivity of ketimine substrates. A highly enantioselective [3+2] cycloaddition reaction that makes use of isatin‐derived ketimines as reaction partners was developed. Notably, both simple and γ‐substituted allenoates could be utilized, and various 3,2′‐pyrrolidinyl spirooxindoles with a tetrasubstituted stereocenter were obtained in excellent yields and with nearly perfect enantioselectivity (>98 % ee in all cases).     

Organocatalytic Enantioselective Synthesis of Pyrazoles Bearing a Quaternary Stereocenter

An efficient one‐pot asymmetric synthesis of pyrazoles bearing a chiral quaternary stereocenter has been developed. Quinine‐derived thiourea catalyzed the enantioselective addition of pyrazolones to isatin‐derived ketimines, providing the corresponding acetylated pyrazoles after in situ treatment with Ac₂O/Et₃N. The corresponding pyrazoles were afforded in high yields and excellent enantioselectivities.     

氨基膦氧类有机小分子催化剂的制备及其催化的对N-取代苯乙酮亚胺的不对称硅氢化还原

首次利用L-酒石酸和L-扁桃酸对吡咯烷/哌啶衍生的氨基膦氧化合物进行拆分制得高对映选择性的氨基膦氧类有机小分子催化剂。将其应用于N-取代苯乙酮亚胺的不对称硅氢化还原反应中,以中等收率和对映体选择性获得相应的N-取代苯基手性胺。