The first primary aminocatalytic direct cross-aldol reaction of acetaldehyde is presented. Among the various vicinal diamines screened, the L-tert-leucine derivative 1c in conjunction with (H4SiW12O40)0.25 was identified as the optimal catalyst; good catalytic activity (up to 99 % yield in 4 h), and high enantioselectivities (up to 92 % ee) were achieved for a range of donors, including aromatic aldehydes
Organocatalytic Direct Asymmetric Crossed-Aldol Reactions of Acetaldehyde in Aqueous Media
作者:Yupu Qiao、Qiankun Chen、Sirong Lin、Bukuo Ni、Allan D. Headley
DOI:10.1021/jo302442g
日期:2013.3.15
dioctylamino group in the presence of a newly developed ionic liquid supported (ILS) benzoic acid as cocatalyst, is shown to be an effective catalytic system for the asymmetricdirectcrossed-aldolreaction of acetaldehyde in aqueous media using brine. For the reactions studied, the catalyst loading could be reduced to 5 mol %; high yields (up to 97%) and high enantioselectivities (up to 92% ee) were also
Highly enantioselective tandem enzyme–organocatalyst crossed aldol reactions with acetaldehyde in deep-eutectic-solvents
作者:Christoph R. Müller、Isabell Meiners、Pablo Domínguez de María
DOI:10.1039/c4ra09307k
日期:——
have emerged as promising bio-based and cost-effective reaction media. Herein, the first concept of tandem catalysis of enzymes and organocatalysts in such environmentally-friendly DES is reported, focusing on enzymatic in situ acetaldehyde production combined with highly enantioselective crossed aldehyde–aldehyde C–C bond formation organocatalysis. This leads to an integrative concept with straightforward
Tandem Catalysis by Lipase in a Vinyl Acetate-Mediated Cross-Aldol Reaction
作者:Manjeet Kumar、Bhahwal A. Shah、Subhash C. Taneja
DOI:10.1002/adsc.201000980
日期:2011.5
The lipase Novozym435 (0.6% w/w) was used in tandem with organocatalysts in a first vinyl/isopropenyl acetate‐mediated aldol reaction. The reaction was facilitated through the lipase‐catalyzed in situ generation of acetaldehyde/acetone. The important features of the present methodology include the mild and facile reaction conditions, regenerability of the lipase, comparatively high yields and minimal
Synthesis of α,β-Unsaturated δ-Lactones by Vinyl Acetate Mediated Asymmetric Cross-Aldol Reaction of Acetaldehyde: Mechanistic Insights
作者:Manjeet Kumar、Arvind Kumar、Masood Rizvi、Manoj Mane、Kumar Vanka、Subhash C. Taneja、Bhahwal Ali Shah
DOI:10.1002/ejoc.201402551
日期:2014.8
using this methodology we have accessed α,β-unstaurated δ-lactones as well as isochromenones with high enantioselectivities from both asymmetric β-hydroxy aldehydes and ketones. Systemic density functional theory (DFT) studies were also performed to gain mechanisticinsights into the role of hydrogen bonding in the asymmetric cross-aldol reaction of acetaldehyde and in the key cis/trans isomerisation