2983-37-1Relevant articles and documents
N-Heterocyclic Carbene/Carboxylic Acid Co-Catalysis Enables Oxidative Esterification of Demanding Aldehydes/Enals, at Low Catalyst Loading
Berkessel, Albrecht,Biswas, Animesh,Harnying, Wacharee,Sudkaow, Panyapon
supporting information, p. 19631 - 19636 (2021/08/09)
We report the discovery that simple carboxylic acids, such as benzoic acid, boost the activity of N-heterocyclic carbene (NHC) catalysts in the oxidative esterification of aldehydes. A simple and efficient protocol for the transformation of a wide range of sterically hindered α- and β-substituted aliphatic aldehydes/enals, catalyzed by a novel and readily accessible N-Mes-/N-2,4,6-trichlorophenyl 1,2,4-triazolium salt, and benzoic acid as co-catalyst, was developed. A whole series of α/β-substituted aliphatic aldehydes/enals hitherto not amenable to NHC-catalyzed esterification could be reacted at typical catalyst loadings of 0.02–1.0 mol %. For benzaldehyde, even 0.005 mol % of NHC catalyst proved sufficient: the lowest value ever achieved in NHC catalysis. Preliminary studies point to carboxylic acid-induced acceleration of acyl transfer from azolium enolate intermediates as the mechanistic basis of the observed effect.
Catalytic decomposition of cumene hydroperoxide
Nurullina,Batyrshin,Kharlampidi
, p. 441 - 444 (2007/10/03)
Cumene hydroperoxide degradation in chlorobenzene in the presence of zinc, cadmium, and mercury 2-ethylhexanoates was studied. The kinetic and thermodynamic parameters of the reaction were determined. It was assumed that the change in the catalytic activity of Group IIB metal compounds is due to the polarizing action of metal ions.
α-ALKYLATION AND α-ALKYLIDENATION OF CARBONYL COMPOUNDS BY O-SILYLATED ENOLATE PHENYLTHIOALKYLATION
Paterson, Ian
, p. 4207 - 4220 (2007/10/02)
For many reactions next to a carbonyl group, the use of O-silylated enolate chemistry offers improvements in yield and selectivity over the corresponding reactions of Group I metal enolates.In the case of α-alkylation of carbonyl compounds, Lewis acid (TiCl4 or ZnBr2) promoted phenylthioalkylation of O-silylated enolates 3 by α-chlorosulphides 4 (R3=H, Me, Prn, Pri, Bui, and Me3Si), followed by reductive sulphur removal by Raney nickel, 5->6, is found to be a reliable method for this synthetically important C-C bond forming step.An alternative sulphur elimination pathway via the sulphoxide, 5->7, allows the regio- and stereocontrolled α-alkylidenation of carbonyl compounds.The phenylthioalkylation reaction is applicable to ketones, aldehydes, esters, and lactones.
