Oxa-Michael addition promoted by the aqueous sodium carbonate
摘要:
An efficient Michael addition of alcohols to activated alkenes promoted by sodium carbonate with water as reaction medium has been developed. The reaction provides a general, economical and environmentally friendly approach for the synthesis of beta-alkoxycarbonyl compounds. (C) 2014 Elsevier Ltd. All rights reserved.
N-silyl oxyketene imines are underused yet highly versatile reagents for catalytic asymmetric synthesis
作者:Scott E. Denmark、Tyler W. Wilson
DOI:10.1038/nchem.857
日期:2010.11
process, arguably the most characteristic reaction of d1 synthetic equivalents, finds no general solution for reactions involving aliphatic acyl anions. In this Article, we introduce a new class of stable, isolable silyl ketene imines derivedfrom protected cyanohydrins. These nucleophiles serve as acyl anion equivalents in Lewis base catalysed aldol addition reactions and allow for the preparation of cross-benzoin
Synthesis of Optically Active α-Hydroxy Carbonyl Compounds by the Catalytic, Enantioselective Oxidation of Silyl Enol Ethers and Ketene Acetals with (Salen)manganese(III) Complexes
作者:Waldemar Adam、Rainer T. Fell、Veit R. Stegmann、Chantu R. Saha-Möller
DOI:10.1021/ja9726668
日期:1998.2.1
A set of silyl enol ethers and ketene acetals 1a−h with α- and/or β-phenyl as well as alkyl substituents of different steric bulk has been submitted to the enantioselective catalytic oxidation by chiral (salen)MnIII complexes 3. Highest conversions and best enantioselectivities have been obtained with bleach rather than iodosobenzene as oxygen source for the active oxo−metal species. With regard to
Solid acid–chiral amine hybrids have been synthesized and explored as recyclable and reusable enamine-type asymmetriccatalysts. Simple chiralamine–polyoxometalate (CA–POM) hybrids were identified as the optimal catalysts to promote a range of enamine-based transformations with high activity and excellent stereoselectivity under either neat or aqueousconditions. A catalyst loading as low as 0.33 mol-%
The catalytic asymmetric synthesis of chiral 2‐hydroxy ketones by using different thiaminediphosphatedependent enzymes, namely benzaldehydelyase from Pseudomonas fluorescens (PfBAL), a variant of benzoylformate decarboxylase from Pseudomonas putida (PpBFD‐L461A), branched‐chain 2‐keto acid decarboxylase from Lactococcus lactis (LlKdcA) and a variant of pyruvate decarboxylase from Acetobacter pasteurianus
Cross-benzoin condensation catalyzed by NHC, prepared from chiral triazolium salts bearing a pyridine ring, afforded α-hydroxy ketones with reasonable chemical yields and enantioselectivities. A wide range of aliphatic and aromatic aldehydes were successfully used in the reaction.