69653-76-5Relevant 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.
Environmental degradation of the insect growth regulator methoprene (isopropyl (2E,4E) 11 methoxy 3,7,11 trimethyl 2,4 dodecadienoate). I. Metabolism by alfalfa and rice
Quistad,Staiger,Schooley
, p. 582 - 589 (2007/10/12)
The metabolic fate of isopropyl (2E, 4E) 11 methoxy 3,7,11 trimethyl 2,4 dodecadienoate, a new insect growth regulator (common name, methoprene; trademark Altosid), was studied in alfalfa and rice as a function of time. The major metabolic pathways involved ester hydrolysis, O demethylation, and oxidative scission of the 4 ene double bond. The principal nonpolar metabolite was 7 methoxycitronellal which was isolated from vapors evolved from the plants. Chromatographic evidence strongly suggests the incorporation of radiolabel from the extensively degraded (2E) [5 14C]methoprene molecule into carotenoids, chlorophylls, and other higher molecular weight plant constituents. Yields of primary metabolites were grossly inflated (10x too high) unless thin layer chromatography was accompanied by prior purification by gel permeation chromatography, because much radioactivity was attributed to coeluting natural products. Rapid metabolism of methoprene to biologically inocuous derivatives was characteristic of both rice and alfalfa.
