35190-16-0Relevant academic research and scientific papers
Selective Synthesis of Acylated Cross-Benzoins from Acylals and Aldehydes via N-Heterocyclic Carbene Catalysis
Onodera, Kou,Suzuki, Yumiko,Takashima, Ryo
supporting information, p. 4197 - 4202 (2021/06/27)
The utility of acylals as building blocks for selective cross-benzoin synthesis was explored in this study. The synthesis of α-acetoxyketones (O-acyl cross-benzoins) was achieved via selective N-heterocyclic carbene-catalyzed cross-benzoin reactions using acylals as aldehyde equivalents. Thus, the combination of ortho-substituted phenyl acylals and aromatic/aliphatic aldehydes as coupling substrates using bicyclic triazolium salts as precatalysts and potassium carbonate as a base in THF at reflux temperature selectively yielded O-acyl cross-benzoins.
Enantioselective N-heterocyclic carbene-catalysed intermolecular crossed benzoin condensations: Improved catalyst design and the role of in situ racemisation
Delany, Eoghan G.,Connon, Stephen J.
supporting information, p. 248 - 258 (2021/01/14)
The enantioselective intermolecular crossed-benzoin condensation mediated by novel chiral N-heterocyclic carbenes derived from pyroglutamic acid has been investigated. A small library of chiral triazolium ions were synthesised. Each possessed a tertiary alcohol H-bond donor and a variable N-aryl substituent. It was found that increasing both the steric requirement and the electron-withdrawing characteristics of the N-aryl ring led to more chemoselective, efficient and enantioselective chemistry, however both quenching the reaction at different times and deuterium incorporation experiments involving the product revealed that this is complicated by product racemisation in situ (except in the case of benzoin itself), which explains the dependence of enantioselectivity on the electrophilicity of the reacting aldehydes common in the literature. Subsequent protocol optimisation, where one reacting partner was an o-substituted benzaldehyde, allowed a range of crossed-benzoins to be synthesised in moderate-good yields with moderate to excellent enantioselectivity.
NaBrO3/bmim[HSO4]: a versatile system for the selective oxidation of 1,2-diols, α-hydroxyketones, and alcohols
Khurana, Jitender M.,Lumb, Anshika,Chaudhary, Ankita
, p. 381 - 386 (2017/02/10)
Abstract: Sodium bromate with bmim[HSO4] has been found to be an excellent oxidizing agent in aqueous medium. NaBrO3:bmim[HSO4] oxidized 1,2-diols, α-hydroxyketones, and alcohols to the corresponding carbonyl compounds in excellent yields. This method offers advantages such as low cost reagents, aqueous reaction conditions, moderate temperatures and short reaction times and hence environmentally benign reaction. Moreover, the ionic liquid bmim[HSO4] could be recycled for at least three times without loss of significant activity. Graphical abstract: [Figure not available: see fulltext.]
Highly chemoselective direct crossed aliphatic-aromatic acyloin condensations with triazolium-derived carbene catalysts
O'Toole, Sarah E.,Rose, Christopher A.,Gundala, Sivaji,Zeitler, Kirsten,Connon, Stephen J.
supporting information; experimental part, p. 347 - 357 (2011/04/17)
It has been shown for the first time that triazolium precatalysts promote (in the presence of base) highly chemoselective crossed acyloin condensation reactions between aliphatic and ortho-substituted aromatic aldehydes. An o-bromine atom can serve as a temporary directing group to ensure high chemoselectivity (regardless of the nature of the other substituents on the aromatic ring) which then can be conveniently removed. The process is of broad scope and is operationally simple as it does not require the preactivation of any of the coupling partners to ensure selectivtiy. Preliminary data indicate that highly enantioselective variants of the reaction are feasible using chiral precatalysts.
α,β-unsaturated aldehydes as substrates for asymmetric C-C bond forming reactions with thiamin diphosphate (ThDP)-dependent enzymes
Cosp, Anabel,Dresen, Carola,Pohl, Martina,Walter, Lydia,Roehr, Caroline,Mueller, Michael
experimental part, p. 759 - 771 (2009/04/10)
The enzymes benzaldehyde lyase (BAL) from Pseudomonas fluorescens, benzoylformate decarboxylase (BFD) from Pseudomonas putida and pyruvate decarboxylase (PDC) from Saccharomyces cerevisiae provide different C-C bond forming possibilities of α,β-unsaturated aldehydes with aliphatic and aromatic aldehydes. Structure elucidation and determination of the absolute configuration of the products, which were obtained with high regio- and stereoselectivity were carried out. Selective 1,2-reactivity with yields of 75% and >98% ee, for one single isomer (A) were obtained, by choosing the suitable enzyme in combination with the appropriate substrates. By varying enzymes or substrates the regioisomeric hydroxy ketones C, with up to >99% ee, can be obtained. The application of these new chiral building blocks in the synthesis of natural products or biological active substances is considerably facilitated by applying the different ThDP-dependent enzymes as catalysts.
One-step assembly of functionalized γ-butyrolactones from benzoins or benzaldehydes via an N-heterocyclic carbene-mediated tandem reaction
Ye, Wei,Cai, Guanliang,Zhuang, Zeyang,Jia, Xueshun,Zhai, Hongbin
, p. 3769 - 3771 (2007/10/03)
(Chemical Equation Presented) We describe here a direct, efficient, one-step construction of γ,γ-difunctionalized γ-butyrolactones from benzoins or benzaldehydes via a tandem reaction promoted by 1,3-dimethyl imidazolin-2-ylidene, an N-heterocyclic carbene (NHC).
THE REDUCTION OF AROMATIC ALDEHYDES AND BENZILS BY SODIUM FORMALDEHYDE SULPHOXYLATE
Harris, Alan R.,Mason, Timothy J.
, p. 529 - 536 (2007/10/02)
Sodium formaldehyde sulphoxylate is shown to be an effective reagent for the reduction of some aromatic aldehydes to alcohols.Benzils are also reduced under neutral or basic conditions to give mainly benzoins.Ketones are reduced only slowly.
