Diastereoselective Lithiation and Substitution of (S)-N-Benzylprolinol and rac-N-Benzylpiperidine-2-methanol via the Carbamate Esters: Kinetic Resolution by Means of (-)-Sparteine-Mediated Deprotonation
Diastereoselective Lithiation and Substitution of (S)-N-Benzylprolinol and rac-N-Benzylpiperidine-2-methanol via the Carbamate Esters: Kinetic Resolution by Means of (-)-Sparteine-Mediated Deprotonation
Enantioselective addition of dialkylzinc reagents to N-(diphenylphosphinoyl)imines catalyzed by β-aminoalcohols with the prolinol skeleton
作者:Raquel Almansa、David Guijarro、Miguel Yus
DOI:10.1016/j.tetasy.2007.11.006
日期:2007.11
Several beta-aminoalcohols with the prolinol framework are shown to be very efficient catalysts for the enantioselective addition of dialkylzinc reagents to N-(diphenylphosphinoyl)imines. The use of 0.5 equiv of the catalyst leads to the expected addition products in good yields and with ee up to 94% in a reaction time of only 4 It at room temperature. This ee is the highest value reported so far using 0.5 equiv of an aminoalcohol as a promoter. High enantioselectivities are obtained in the addition of dialkylzincs to both aromatic and aliphatic imines. The amount of the catalyst can be reduced to 0.25 equiv with a slight decrease in the ee. A very interesting effect of the addition rate and temperature on the enantioselectivity was also observed. (c) 2007 Elsevier Ltd. All rights reserved.
A Convenient Preparation of Difficultly Accessible sec-Alkylmethylphosphinates Using Sequential Pudovik/Abramov - Barton/McCombie Reactions
Diastereoselective Lithiation and Substitution of (S)-N-Benzylprolinol and rac-N-Benzylpiperidine-2-methanol via the Carbamate Esters: Kinetic Resolution by Means of (-)-Sparteine-Mediated Deprotonation