136983-95-4Relevant articles and documents
Preparation of chitosan-supported urea materials and their application in some organocatalytic procedures
de Gonzalo, Gonzalo,Franconetti, Antonio,Fernández, Rosario,Lassaletta, José M.,Cabrera-Escribano, Francisca
, p. 365 - 374 (2018/07/25)
An efficient and mild procedure was developed for the preparation of three chitosan-supported ureas containing electron-withdrawing groups. These catalysts were characterized and employed as organocatalysts in different transformations, including the enan
Dual Lewis Acid/Lewis Base Catalyzed Acylcyanation of Aldehydes: A Mechanistic Study
Laurell Nash, Anna,Hertzberg, Robin,Wen, Ye-Qian,Dahlgren, Bj?rn,Brinck, Tore,Moberg, Christina
, p. 3821 - 3829 (2016/03/08)
A mechanistic investigation, which included a Hammett correlation analysis, evaluation of the effect of variation of catalyst composition, and low-temperature NMR spectroscopy studies, of the Lewis acid-Lewis base catalyzed addition of acetyl cyanide to prochiral aldehydes provides support for a reaction route that involves Lewis base activation of the acyl cyanide with formation of a potent acylating agent and cyanide ion. The cyanide ion adds to the carbonyl group of the Lewis acid activated aldehyde. O-Acylation by the acylated Lewis base to form the final cyanohydrin ester occurs prior to decomplexation from titanium. For less reactive aldehydes, the addition of cyanide is the rate-determining step, whereas, for more reactive, electron-deficient aldehydes, cyanide addition is rapid and reversible and is followed by rate-limiting acylation. The resting state of the catalyst lies outside the catalytic cycle and is believed to be a monomeric titanium complex with two alcoholate ligands, which only slowly converts into the product.
Fast microwave-assisted resolution of (±)-cyanohydrins promoted by lipase from Candida antarctica
Ribeiro, Sandra S.,Ferreira, Irlon M.,Lima, Jo?o P. F.,De Sousa, Bruno A.,Carmona, Rafaela C.,Santos, Alcindo A. Dos,Porto, André L. M.
, p. 1344 - 1350 (2015/07/15)
Enzymatic kinetic resolution (EKR) of (±)-cyanohydrins was performed by using immobilized lipase from Candida antarctica (CALB) under conventional ordinary conditions (orbital shaking) and under microwave radiation (MW). The use of microwave radiation contributed very expressively on the reduction of the reaction time from 24 to 2 h. Most importantly, high selectivity (up to 92percent eep) as well as conversion was achieved under MW radiation (50-56percent).
A homochiral metal-organic framework as an effective asymmetric catalyst for cyanohydrin synthesis
Mo, Ke,Yang, Yuhua,Cui, Yong
supporting information, p. 1746 - 1749 (2014/03/21)
A homochiral metal-organic framework (MOF) of an enantiopure 2,2′-dihydroxy-1,1′-biphenyl ligand was constructed. After exchanging one proton of the dihydroxyl group for Li(I) ions, the framework is shown to be a highly efficient and recyclable heterogene
A simple separation method for (S)-hydroxynitrile lyase from cassava and its application in asymmetric cyanohydrination
Zheng, Zubiao,Zi, Yan,Li, Zhongzhou,Zou, Xinzhuo
, p. 434 - 439 (2013/06/27)
Using an acetone precipitation method, crude (S)-hydroxynitrile lyase [(S)-MeHNL] was separated from Munihot esculenta (cassava) leaves, and used directly as biocatalyst to catalyze asymmetric cyanohydrination and produce cyanohydrins with enantiomeric purities (≥90% ee) significantly greater than those previously reported. The use of a water/i-Pr2O system with an enzyme, NaCN, and appropriate amounts of acetic acid is crucial in improving the stereoselectivity of cyanohydrin formation by minimizing the non-enzymatic reaction and the racemization of the chiral products. The proposed isolation method for crude (S)-MeHNL has a high value because of its simplicity, and low cost as well as the high activity of the crude (S)-MeHNL.
Asymmetric cyanohydrin synthesis using an aluminium(salan) complex
North, Michael,Stewart, Emma L.,Young, Carl
, p. 1218 - 1225,8 (2020/09/09)
The asymmetric addition of trimethylsilyl cyanide to aldehydes catalysed by chiral metal(salan) complexes has been investigated. Salan complexes of titanium and vanadium displayed only low catalytic activity, but a bimetallic aluminium(salan) complex gave
Enantioselective O-acetylcyanation/cyanoformylation of aldehydes using catalysts with built-in crown ether-like motif in chiral macrocyclic V(V) salen complexes
Khan, Noor-Ul H.,Sadhukhan, Arghya,Maity, Nabin C.,Kureshy, Rukhsana I.,Abdi, Sayed H.R.,Saravanan,Bajaj, Hari C.
experimental part, p. 7073 - 7080 (2011/10/07)
Chiral macrocyclic V(V) salen complexes 1a-f derived from macrocyclic ligands obtained by the reaction of 1R,2R-(-) diaminocyclohexane/(1R,2R)-(+)-1, 2-diphenylethylenediamine with bis-aldehydes 2 and 3 were synthesized and used as efficient catalysts in asymmetric cyanation reactions. The V(V) catalysts demonstrated excellent performance (product yields and ees up to 99%) with potassium cyanide (KCN) and sodium cyanide (NaCN). The catalytic system also performed very well with a safer source of cyanide-ethyl cyanoformate to give cyanohydrin carbonates in excellent yield and ee (up to 97%). The V(V) macrocyclic salen complex 1b retained its performance at multi-gram level and was conveniently recycled for a number of times.
Investigation of lewis acid versus lewis base catalysis in asymmetric cyanohydrin synthesis
North, Michael,Omedes-Pujol, Marta,Williamson, Courtney
experimental part, p. 11367 - 11375 (2010/11/17)
The asymmetric addition of trimethylsilyl cyanide to aldehydes can be catalysed by Lewis acids and/or Lewis bases, which activate the aldehyde and trimethylsilyl cyanide, respectively. It is not always apparent from the structure of the catalyst whether Lewis acid or Lewis base catalysis predominates. To investigate this in the context of using salen complexes of titanium, vanadium and aluminium as catalysts, a Hammett analysis of asymmetric cyanohydrin synthesis was undertaken. When Lewis acid catalysis is dominant, a significantly positive reaction constant is observed, whereas reactions dominated by Lewis base catalysis give much smaller reaction constants. [{Ti(salen)O}2] was found to show the highest degree of Lewis acid catalysis, whereas two [VO(salen)X] (X = EtOSO3 or NCS) complexes both displayed lower degrees of Lewis acid catalysis. In the case of reactions catalysed by [{Al(salen)}2O] and triphenyl- phosphine oxide, a non-linear Ham- mett plot was observed, which is indicative of a change in mechanism with increasing Lewis base catalysis as the carbonyl compound becomes more electron-deficient. These results suggested that the aluminium complex/tri- phenylphosphine oxide catalyst system should also catalyse the asymmetric addition of trimethylsilyl cyanide to ke- tones and this was found to be the case.
Kinetics and mechanism of vanadium catalysed asymmetric cyanohydrin synthesis in propylene carbonate
North, Michael,Omedes-Pujol, Marta
experimental part, p. 1043 - 1055 (2011/03/22)
Propylene carbonate can be used as a green solvent for the asymmetric synthesis of cyanohydrin trimethylsilyl ethers from aldehydes and trimethylsilyl cyanide catalysed by VO(salen)NCS, though reactions are slower in this solvent than the corresponding re
Enzymatic kinetic resolution of racemic cyanohydrins via enantioselective acylation
Xu, Qing,Xie, Yongli,Geng, Xiaohong,Chen, Peiran
experimental part, p. 624 - 630 (2010/09/07)
Enzymatic kinetic resolution of a series of aromatic and aliphatic cyanohydrins in organic media has been investigated. The behavior of potential lipases, molecular sieves, acyl reagent, reaction temperature, and organic solvents on the kinetic resolution was studied. The influence of substrate structure, steric, and electronic nature and position of the aryl substituent on the enantioselectivity was discussed. Under the optimized reaction conditions, good enantioselectivity could be achieved for most of the investigated compounds. Specifically, substrates 1a, 1c, 1d, 1f, 1u could be resolved with the kinetic enantiomer ratio (E) higher than 200.
