Chemoenzymatic synthesis of chiral unsymmetrical benzoin esters
作者:Pilar Hoyos、Vittorio Pace、José V. Sinisterra、Andrés R. Alcántara
DOI:10.1016/j.tet.2011.07.030
日期:2011.9
chemoenzymatic Dynamic Kinetic Resolution (DKR) of unsymmetrical benzoins (Ar1≠Ar2) has been carried out, by using Pseudomonas stutzeri lipase stereorecognition pattern. After studying this lipase behaviour, a high preference towards acylation of those benzoins containing substituents in the phenyl ring rather than in the benzoyl moiety was observed. This fact allowed the development of the DKR process of this
A Family of Thiazolium Salt Derived N-Heterocyclic Carbenes (NHCs) for Organocatalysis: Synthesis, Investigation and Application in Cross-Benzoin Condensation
作者:Isabel Piel、Marius D. Pawelczyk、Keiichi Hirano、Roland Fröhlich、Frank Glorius
DOI:10.1002/ejoc.201100870
日期:2011.10
A family of thiazolium salt derived N-heterocycliccarbenes (NHCs) bearing sterically demanding aryl substituents on the nitrogen and with varying backbone substitution patterns have been synthesized. Investigation of the catalytic activity of these NHCs in a number of benzoin-type coupling reactions revealed markedly different levels of reactivity and selectivity. To elucidate the underlying factors
For the first time, the combination of chlorotrimethylsilane with NaI is used as a selective reducting system toward 1,2-diketones. This combination is successfully evaluated with several unsymmetrically benzil derivatives, which are reduced in good yields and with a total α-regioselectivity at room temperature. Identification of benzoin intermediates is achieved, and a mechanistic radical process
Rate and Equilibrium Constants for the Addition of N-Heterocyclic Carbenes into Benzaldehydes: A Remarkable 2-Substituent Effect
作者:Christopher J. Collett、Richard S. Massey、James E. Taylor、Oliver R. Maguire、AnnMarie C. O'Donoghue、Andrew D. Smith
DOI:10.1002/anie.201501840
日期:2015.6.1
Rate and equilibriumconstants for the reaction between N‐aryl triazolium N‐heterocyclic carbene (NHC) precatalysts and substituted benzaldehyde derivatives to form 3‐(hydroxybenzyl)azolium adducts under both catalytic and stoichiometric conditions have been measured. Kinetic analysis and reaction profile fitting of both the forward and reverse reactions, plus onwards reaction to the Breslow intermediate
Lewis Acid-Promoted Friedel−Crafts Alkylation Reactions with α-Ketophosphate Electrophiles
作者:Austin G. Smith、Jeffrey S. Johnson
DOI:10.1021/ol100410k
日期:2010.4.16
The BF3·OEt2-promoted nucleophilicsubstitution of α-aryl-α-ketophosphates to afford α,α-diaryl ketone products is described. Electron-rich α-ketophosphates perform best, with electron-neutral and electron-poor substrates also tolerated. The reaction is tolerant of a range of aromatic, heteroaromatic, and nonaromatic nucleophiles, with yields ranging from 44% to 84%. Enantioenriched starting material
描述了BF 3 ·OEt 2促进的α-芳基-α-酮磷酸盐的亲核取代,以提供α,α-二芳基酮产物。富含电子的α-酮磷酸酯的性能最佳,同时还可以耐受电子中性和贫电子的底物。该反应可耐受多种芳族,杂芳族和非芳族亲核试剂,收率范围为44%至84%。富含对映体的原料产生外消旋产物,表明通过酰基carb离子的S N 1途径。