Straightforward access to oxazaborines, diazaborinones and triazaborines by reactions of β-enaminoamides with 4-methylbenzenediazonium tetraphenylborate
The reaction of substituted beta-enaminoamides with 4-methylbenzenediazonium tetraphenylborate in dichloromethane produces besides the primary products of azo coupling reaction at the alpha-carbon atom of beta-enaminoamides, also mixtures of heterocyclic compounds of boron: 1,3,2 lambda(4)-oxazaborines, 1H-1,3,2 lambda(4)-diazaborine-4-ones and 4H-1,2,4,3 lambda(4)-triazaborines. Proportions of the products change depending on the reaction conditions, particularly depending on the presence or absence of base (sodium acetate) in the reaction mixture. The heterocyclic compounds were separated chromatographically and identified by means of X-ray, H-1, B-11, C-13 and N-15 NMR spectra and elemental analyses. (C) 2008 Elsevier B.V. All rights reserved.
Detection and Elimination of Product Inhibition from the Asymmetric Catalytic Hydrogenation of Enamines
作者:Karl B. Hansen、Thorsten Rosner、Michele Kubryk、Peter G. Dormer、Joseph D. Armstrong
DOI:10.1021/ol051862d
日期:2005.10.1
text] The catalytic asymmetric hydrogenation of enamine amides and esters with catalyst Rh-1a, prepared from ferrocenyl based ligand 1a or 1b and [(COD)RhCl](2), has been shown through kinetic studies to suffer fromproduct inhibition. Enamine ester substrates have also been shown to be incompatible with the amine products of the reaction in methanol. In situ protection of the amine products with di-tert-butyl
Highly Efficient Synthesis of β-Amino Acid Derivatives via Asymmetric Hydrogenation of Unprotected Enamines
作者:Yi Hsiao、Nelo R. Rivera、Thorsten Rosner、Shane W. Krska、Eugenia Njolito、Fang Wang、Yongkui Sun、Joseph D. Armstrong、Edward J. J. Grabowski、Richard D. Tillyer、Felix Spindler、Christophe Malan
DOI:10.1021/ja047901i
日期:2004.8.1
A direct asymmetrichydrogenation of unprotected enamino esters and amides is described. Catalyzed by Rh complexes with Josiphos-type chiral ligands, this method gives beta-amino esters and amides in high yield and high ee (93-97% ee). No acyl protection/deprotection is required.
描述了未保护的烯氨基酯和酰胺的直接不对称氢化。该方法由具有 Josiphos 型手性配体的 Rh 络合物催化,以高产率和高 ee (93-97% ee) 得到 β-氨基酯和酰胺。不需要酰基保护/脱保护。