1383986-87-5Relevant academic research and scientific papers
Synthesis of chiral β-amino acid derivatives by asymmetric hydrosilylation with an imidazole derived organocatalyst
Jones, Simon,Li, Xianfu
experimental part, p. 5522 - 5532 (2012/09/21)
The organocatalysed asymmetric hydrosilylation of a number of N-aryl and alkyl β-substituted enamino esters proceeds in generally good yield and enantioselectivity. Crucial to obtaining high yield and selectivity was the addition of benzoic acid as an additive and under these conditions, both N-alkyl and N-aryl substituents were well tolerated. β-Aryl and alkyl substituents were evaluated and a model proposed to account for the experimental observations based upon enamine tautomerisation and conformational preferences of the reactive ketimine intermediate.
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
supporting information; 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.
Dynamic kinetic resolution in the asymmetrie synthesis of β-amino acids by organocatalytic reduction of enamines with trichlorosilane
Malkov, Andrei V.,Stoncius, Sigitas,Vrankova, Kvetoslava,Arndt, Matthias,Kocovsky, Pavel
supporting information; experimental part, p. 8082 - 8085 (2009/09/29)
A new methodology based on the organocatalytic asymmetric hydrosilylation of enamines that allows a direct access to a range of β3 and β2.3-amino acid derivatives was presented. The results show a successful reduction of aromatic substrates, a sterically more hindered ortho-substituted derivatives, and the thiophenyl analogue exhibiting lower reactivity. Fast enamine-imine equilibration is crucial as imines are chiral but racemic, while α-alkyl β-amino acids can be accessed by the symmetrical Mannich reaction. The α-alkyl derivatives have relative and absolute configuration due to their reduction with LiAlH4 into a known amino alcohols. Predominant formation of the anti isomer in 3o is consistent with conformation of the imine intermediate in the catalytic reduction.
