00938nas a2200169 4500008004100000022001400041245008100055210006900136260010600205300001200311490000700323520027200330100002000602700002300622700001900645856010400664 2010 eng d a0040-403900aPivaloyl chloride/DMF: a new reagent for conversion of alcohols to chlorides0 aPivaloyl chlorideDMF a new reagent for conversion of alcohols to aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLANDbPERGAMON-ELSEVIER SCIENCE LTDcJAN a744-7460 v513 a

An efficient procedure for conversion of alcohols into the corresponding chlorides is described. Pivaloyl chloride/DMF complex is employed as a mild and inexpensive reagent. A possible reaction mechanism is proposed. (C) 2009 Elsevier Ltd. All rights reserved.

1 aDubey, Abhishek1 aUpadhyay, Arun, K.1 aKumar, Pradeep uhttps://library.ncl.res.in/content/pivaloyl-chloridedmf-new-reagent-conversion-alcohols-chlorides-003350nas a2200157 4500008004100000022001400041245010100055210006900156260007100225300001200296490000700308520270900315100001903024700002103043856012803064 2013 eng d a0001-484200aProline catalyzed alpha-aminoxylation reaction in the synthesis of biologically active compounds0 aProline catalyzed alphaaminoxylation reaction in the synthesis o a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcFEB a289-2990 v463 a

The search for new and efficient ways to synthesize optically pure compounds is an active area of research in organic synthesis. Asymmetric catalysis provides a practical, cost-effective, and efficient method to create a variety of complex natural products containing multiple stereocenters. In recent years, chemists have become more interested in using small organic molecules to catalyze organic reactions. As a result, organocatalysis has emerged both as a promising strategy and as an alternative to catalysis with expensive proteins or toxic metals. One of the most successful and widely studied secondary amine-based organocatalysts is proline. This small molecule can catalyze numerous reactions such as the aldol, Mannich, Michael addition, Robinson annulation, Diels-Alder, alpha-functionalization, alpha-amination, and alpha-aminoxylation reactions. Catalytic and enantioselective alpha-oxygenation of carbonyl compounds is an important reaction to access a variety of useful building blocks for bioactive molecules. Proline catalyzed alpha-aminoxylation using nitrosobenzene as oxygen source, followed by in situ reduction, gives enantiomerically pure 1,2-diol. This molecule can then undergo a variety of organic reactions. In addition, proline organocatalysis provides access to an assortment of biologically active natural products including mevinoline (a cholesterol lowering drug), tetrahydrolipstatin (an antiobesity drug), R(+)-alpha-lipoic acid, and bovidic acid. In this Account, we present an iterative organocatalytic approach to synthesize both syn- and anti-1,3-polyols, both enantio- and stereoselectively. This method is primarily based on proline-catalyzed sequential alpha-aminoxylation and Horner-Wadsworth-Emmons (HWE) olefination of aldehyde to give a gamma-hydroxy ester. In addition, we briefly illustrate the broad application of our recently developed strategy for 1,3-polyols, which serve as valuable, enantiopure building blocks for polyketides and other structurally diverse and complex natural products. Other research groups have also applied similar strategies to prepare such bioactive molecules as littoralisone, brasoside and (+)-cytotrienin A. Among the various synthetic approaches reported for 1,3-polyols, our organocatalytic iterative approach appears to be very promising and robust. This method combines the merit of organocatalytic reaction with an easy access to both enantiomerically pure forms of proline, mild reaction conditions, and tolerance to both air and moisture. In this Account, we present the latest applications of organocatalysis and how organic chemists can use this new tool for the total synthesis of complex natural products

1 aKumar, Pradeep1 aDwivedi, Namrata uhttps://library.ncl.res.in/content/proline-catalyzed-alpha-aminoxylation-reaction-synthesis-biologically-active-compounds-000956nas a2200169 4500008004100000022001400041245007300055210006800128260007100196300001600267490000700283520032800290100001900618700002000637700002400657856010500681 2013 eng d a0022-326300aProline-catalyzed asymmetric synthesis of syn- and anti-1,3-diamines0 aProlinecatalyzed asymmetric synthesis of syn and anti13diamines a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcDEC a11756-117640 v783 a

A general organocatalytic strategy for asymmetric synthesis of both syn/anti-1,3-diamines has been developed. The strategy employs proline-catalyzed sequential alpha-amination and Horner-Wadsworth-Emmons (HWE) olefination of aldehydes as the key step where syn-1,3-diamine was obtained as the most favorable product.

1 aKumar, Pradeep1 aJha, Vishwajeet1 aGonnade, Rajesh, G. uhttps://library.ncl.res.in/content/proline-catalyzed-asymmetric-synthesis-syn-and-anti-13-diamines-001964nas a2200145 4500008004100000245008400041210006900125260000800194300001400202490000700216520144400223100001901667700002401686856010801710 2018 eng d00aProline-catalyzed asymmetric -amination in the synthesis of bioactive molecules0 aProlinecatalyzed asymmetric amination in the synthesis of bioact cJUN a1944-19560 v293 aThe direct -amination of carbonyl compounds using organocatalysts represents a powerful and atom-economical tool for asymmetric C-N bond formation. We describe a complete account of -functionalization of carbonyl compounds, through iterative sequential -aminoxylation/amination using electrophilic O and N sources, as well as sequential -amination/HWE reaction for enantio- and diastereoselective synthesis of both syn - and anti -1,3-aminoalcohols and 1,3-diamines. Additionally this protocol is further extended for the easy construction of alkaloids such as indolizidine, pyrrolizidine, and quinolizidine fused-ring systems just by tuning the chain length of the aldehyde used as a starting material. This methodology provides further scope to extrapolate it for a variety of naturally occurring hydroxylated monocyclic and fused bicyclic pyrrolidine and piperidine based alkaloids such as lentiginosine, epi -lentiginosine, dihydroxypyrrolizidine, (+)-deoxoprosophylline and (-)-deoxoprosopinine alkaloids. Furthermore, we have also uncovered proline-catalyzed anti -selectivity for the synthesis of 1,2-amino alcohols in -amination of aldehyde and one-pot indium-mediated Barbier type allylation of -hydrazino aldehydes to accomplish the total synthesis of clavaminols, sphinganine and spisulosine with reduced number of steps and with high overall yields. 1 Introduction 2 Application in the Total Synthesis of Alkaloids 3 Conclusion1 aKumar, Pradeep1 aSharma, Brijesh, M. uhttps://library.ncl.res.in/content/proline-catalyzed-asymmetric-amination-synthesis-bioactive-molecules