Showing papers by "Vinod K. Singh published in 2009"
TL;DR: This feature article has described reactions promoted by organocatalysts in a large excess of water, without any organic solvent or excess of any reactant.
268 citations
TL;DR: The results demonstrate that the structural features of organocatalysts play a crucial role in obtaining high optical purity of aldol adducts in an aqueous medium and the role of water in increasing the rate and enantioselectivity of the reaction has been illustrated.
Abstract: A series of highly efficient organocatalysts have been derived from naturally available amino acids for carrying out enantioselective direct aldol reaction in both organic and aqueous medium. The aldol products were obtained in high diastereoselectivities (up to 99:1) and enantioselectivities (up to >99% ee) for a broader range of substrates using 1 mol % of a catalyst. The results demonstrate that the structural features of organocatalysts play a crucial role in obtaining high optical purity of aldol adducts in an aqueous medium. Further, the role of water in increasing the rate and enantioselectivity of the reaction has been illustrated. Moreover, the aldol products have been employed in the synthesis of chiral amino alcohols which act as useful intermediates for building up complex natural products.
122 citations
TL;DR: A copper(II) complex of C2-symmetric diamine has been proved to be an efficient catalyst for the enantioselective Henry reaction between nitroalkanes and various aldehydes as discussed by the authors.
Abstract: A copper(II) complex of C2-symmetric diamine has been proved to be an efficient catalyst for the enantioselective Henry reaction between nitroalkanes and various aldehydes to provide β-hydroxy nitroalkanes in high yields (up to 97%), moderate diastereoselectivities (up to 71:29) and excellent enantiomeric excesses (up to 96%). The chiral nitroaldol adduct obtained has been further converted into chiral aziridine in few steps.
67 citations
TL;DR: In this article, a general synthetic approach was developed for the asymmetric synthesis of chiral δ-lactones and verbalactone using d -glucose. The key intermediate used in this approach was α-diazoketone.
15 citations
TL;DR: A copper(II) complex of C2-symmetric diamine has been proved to be an efficient catalyst for the enantioselective Henry reaction between nitroalkanes and various aldehydes as discussed by the authors.
Abstract: A copper(II) complex of C2-symmetric diamine has been proved to be an efficient catalyst for the enantioselective Henry reaction between nitroalkanes and various aldehydes to provide β-hydroxy nitroalkanes in high yields (up to 97%), moderate diastereoselectivities (up to 71:29) and excellent enantiomeric excesses (up to 96%). The chiral nitroaldol adduct obtained has been further converted into chiral aziridine in few steps.
1 citations
TL;DR: In this article, the catalytic enantioselective Friedel-Crafts reaction of indoles with 2-enoylpyridine 1-oxides has been studied in the presence of chiral pyridine 2,6-bis(5',5'-diphenyloxazoline)-Cu(II) complexes.
Abstract: The catalytic enantioselective Friedel-Crafts reaction of indoles with 2-enoylpyridine 1-oxides has been studied in the presence of chiral pyridine 2,6-bis(5',5'-diphenyloxazoline)-Cu(II) complexes. The reaction furnished alkylated indoles in excellent yields (up to 97%) and enantioselectivities (up to 99% ee).
TL;DR: In this article, a series of highly efficient organocatalysts have been derived from naturally available amino acids for carrying out enantioselective direct aldol reaction in both organic and aqueous medium.
Abstract: A series of highly efficient organocatalysts have been derived from naturally available amino acids for carrying out enantioselective direct aldol reaction in both organic and aqueous medium. The aldol products were obtained in high diastereoselectivities (up to 99:1) and enantioselectivities (up to >99% ee) for a broader range of substrates using 1 mol % of a catalyst. The results demonstrate that the structural features of organocatalysts play a crucial role in obtaining high optical purity of aldol adducts in an aqueous medium. Further, the role of water in increasing the rate and enantioselectivity of the reaction has been illustrated. Moreover, the aldol products have been employed in the synthesis of chiral amino alcohols which act as useful intermediates for building up complex natural products.