326894-40-0Relevant articles and documents
Asymmetric reduction of imines with trichlorosilane, catalyzed by sigamide, an amino acid-derived formamide: Scope and limitations
Malkov, Andrei V.,Vrankova, Kvetoslava,Stoncius, Sigitas,Kocovsky, Pavel
experimental part, p. 5839 - 5849 (2009/12/26)
(Chemical Equation Presented) Enantioselective reduction of ketimines 6-10 with trichlorosilane can be catalyzed by the N-methyl valine-derived Lewis-basic formamide (S)-23 (Sigamide) with high enantioselectivity (≤97% ee) and low catalyst loading (1-5 mol %) at room temperature in toluene. The reaction is efficient with ketimines derived from aromatic amines (aniline and anisidine) and aromatic, heteroaromatic, conjugated, and even nonaromatic ketones 1-5, in which the steric difference between the alkyl groups R1 and R 2 is sufficient. Simple nitrogen heteroaromatics (8a,b,d) exhibit low enantioselectivities due to the competing coordination of the reagent but increased steric hindrance in the vicinity of the nitrogen (8c,e) results in a considerable improvement. Cyclic imines 32d-d exhibited low to modest enantioselectivities.
Facile asymmetric synthesis of α-amino acids employing chiral ligand-mediated asymmetric addition reactions of phenyllithium with imines
Hasegawa, Masayoshi,Taniyama, Daisuke,Tomioka, Kiyoshi
, p. 10153 - 10158 (2007/10/03)
A three-step methodology involving an external chiral ligand-mediated asymmetric addition of phenyllithium to an anisidine imine, oxidative removal of N-PMP group, and finally oxidative conversion of the phenyl group to a carboxyl group provides a facile synthesis of optically pure α-amino acid derivatives beating a bulky α-substituent. (C) 2000 Elsevier Science Ltd.
