The proline-derived N-sulfonylcarboxamide-catalyzed direct enantioselective alpha-oxidation of ketones and aldehydes with nitrosobenzene is presented. The reactions proceed smoothly furnishing the corresponding alpha-aminoxylated compounds in good yields with up to > 99% ee. The proline-derived N-sulfonylcarboxamides were also found to be excellent catalysts for the direct enantioselective nitroso Diels-Alder-type reaction between nitrosobenzene and of alpha,beta-unsaturated cyclic ketones yielding the corresponding bicyclic Diels-Alder adduct products with tip to > 99% ee. The proline-derived N-sulfonylcarboxamides represent a readily available and highly modular novel type of organic catalyst. (c) 2005 Elsevier Ltd. All rights reservesd.
Direct Amino Acid-Catalyzed Asymmetric Desymmetrization of <i>meso</i>-Compounds: Tandem Aminoxylation/O−N Bond Heterolysis Reactions
作者:Dhevalapally B. Ramachary、Carlos F. Barbas
DOI:10.1021/ol050246e
日期:2005.4.14
A practical organocatalytic process for the synthesis of optically active, highly substituted (x-hydroxy-ketones was achieved through asymmetric desymmetrization (ADS) of prochiral ketones. The ADS and O-N bond reduction reaction of prochiral ketone with nitrosobenzene in the presence of a catalytic amount of chiral amine or amino acid produced the tandem ADS/O-N bond reduced products as single diastereomers with good yields and excellent enantiomeric excesses.