@article { ISI:000343847700007, title = {New organocatalyst derived from abietic acid and 4-hydroxy-L-proline for direct asymmetric aldol reactions in aqueous media}, journal = {Tetrahedron-Asymmetry}, volume = {25}, number = {18-19}, year = {2014}, month = {OCT}, pages = {1292-1297}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, type = {Article}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

Enantioselective direct aldol reactions were carried out in aqueous media with a new organocatalyst that was derived from 4-hydroxy-L-proline and abietic acid via a simple and convenient synthetic protocol with a high overall yield (75\%). The new organocatalyst was used for aldol reactions between substituted aromatic aldehydes and various ketones in the presence of several acid additives in aqueous media. The corresponding aldol products were obtained in high isolated yields (up to 99\%) and with high anti-diastereoselectivities (up to 94\%) and enantioselectivities (\>99.9\%). The catalyst loading can be efficiently reduced to only 1 mol \%. The aldol reactions were found to be extremely fast which is very unusual in organocatalyzed reactions in water. (C) 2014 Elsevier Ltd. All rights reserved.

}, issn = {0957-4166}, doi = {10.1016/j.tetasy.2014.07.012}, author = {Bhowmick, Sudipto and Kunte, Sunita S. and Bhowmick, Kartick C.} } @article { ISI:000338042500053, title = {Smallest organocatalyst in highly enantioselective direct aldol reaction in wet solvent-free conditions}, journal = {RSC Advances}, volume = {4}, number = {46}, year = {2014}, month = {MAY}, pages = {24311-24315}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

The catalytic efficacy of the smallest organocatalyst, L-proline hydrazide, prepared from a cheaply available natural amino acid, such as L-proline, was studied for the direct asymmetric aldol reaction of various ketones with aromatic aldehydes at room temperature in the presence of several acid additives. A loading of 10 mol\% of catalyst 1 and p-toluenesulphonic acid as an additive was employed in this reaction, and good yields (up to 99\%) with high anti/syn diastereoselectivities (up to 95 : 5) and enantioselectivities (up to \>99.9\%) were achieved in aqueous media.

}, issn = {2046-2069}, doi = {10.1039/c4ra02690j}, author = {Bhowmick, Sudipto and Kunte, Sunita S. and Bhowmick, Kartick C.} } @article { ISI:000348245000002, title = {Comprehensive study on the effect of acid additives in 1(R),2(R)-Bis[(S)-prolinamido]cyclohexane catalyzed direct asymmetric aldol reactions in aqueous media}, journal = {Indian Journal of Chemistry Section B-Organic Chemistry Including Medicinal Chemistry}, volume = {54}, number = {1}, year = {2015}, month = {JAN}, pages = {84-92}, publisher = {COUNCIL SCIENTIFIC \& INDUSTRIAL RES}, address = {ANUSANDHAN BHAWAN, 2 RAFI MARG, NEW DELHI, 110001, INDIA}, abstract = {

The catalytic efficacy of (1R,2R)-bis[(S)-prolinamido]cyclohexane 1, prepared from the readily available natural amino acid L-proline has been studied for the direct asymmetric aldol reaction of cyclohexanone with substituted benzaldehydes at room temperature in presence of various acid additives. A wide variety of acids e.g. aliphatic fatty acid, chiral acid, sulphonic acid, aromatic acid, etc. have been used as additive for the aldol reaction in aqueous media. A loading of 10 mol\% of catalyst 1 is employed in this reaction, and good yields (up to 98\% yield), diastereoselectivity (up to 96\% de) and enantioselectivities (up to 87\% ee) can be achieved in aqueous media within very short reaction time (1-4 hours).

}, keywords = {acid additives, aqueous media, Asymmetric synthesis, direct aldol reaction, organocatalysis}, issn = {0376-4699}, author = {Bhowmick, Sudipto and Kunte, Sunita S. and Bhowmick, Kartick C.} }