01565nas a2200169 4500008004100000022001400041245012800055210006900183260010600252300001400358490000700372520081800379100002201197700002201219700002601241856012801267 2014 eng d a0957-416600aNew organocatalyst derived from abietic acid and 4-hydroxy-L-proline for direct asymmetric aldol reactions in aqueous media0 aNew organocatalyst derived from abietic acid and 4hydroxyLprolin aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLANDbPERGAMON-ELSEVIER SCIENCE LTDcOCT a1292-12970 v253 a

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.

1 aBhowmick, Sudipto1 aKunte, Sunita, S.1 aBhowmick, Kartick, C. uhttp://library.ncl.res.in/content/new-organocatalyst-derived-abietic-acid-and-4-hydroxy-l-proline-direct-asymmetric-aldol-001319nas a2200169 4500008004100000022001400041245010800055210006900163260011000232300001600342490000600358520058800364100002200952700002200974700002600996856012701022 2014 eng d a2046-206900aSmallest organocatalyst in highly enantioselective direct aldol reaction in wet solvent-free conditions0 aSmallest organocatalyst in highly enantioselective direct aldol  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcMAY a24311-243150 v43 a

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.

1 aBhowmick, Sudipto1 aKunte, Sunita, S.1 aBhowmick, Kartick, C. uhttp://library.ncl.res.in/content/smallest-organocatalyst-highly-enantioselective-direct-aldol-reaction-wet-solvent-free-001671nas a2200229 4500008004100000022001400041245016200055210006900217260010300286300001000389490000700399520073200406653001901138653001801157653002501175653002601200653002001226100002201246700002201268700002601290856012501316 2015 eng d a0376-469900aComprehensive study on the effect of acid additives in 1(R),2(R)-Bis[(S)-prolinamido]cyclohexane catalyzed direct asymmetric aldol reactions in aqueous media0 aComprehensive study on the effect of acid additives in 1R2RBisSp aANUSANDHAN BHAWAN, 2 RAFI MARG, NEW DELHI, 110001, INDIAbCOUNCIL SCIENTIFIC & INDUSTRIAL REScJAN a84-920 v543 a

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).

10aacid additives10aaqueous media10aAsymmetric synthesis10adirect aldol reaction10aorganocatalysis1 aBhowmick, Sudipto1 aKunte, Sunita, S.1 aBhowmick, Kartick, C. uhttp://library.ncl.res.in/content/comprehensive-study-effect-acid-additives-1r2r-biss-prolinamidocyclohexane-catalyzed-0