Oxidation of α,β-unsaturated methyl ketones with selenium dioxide leads to a cascade of reactions culminating in the formation of isotetronic acids.
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Ni(ii)-Catalyzed vinylic C-H functionalization of 2-acetamido-3-arylacrylates to access isotetronic acids.
Org Biomol Chem
May 2020
Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur-721302, India.
A ligand-free Ni(ii)-catalyzed cascade annulation reaction for the synthesis of 4-aryl-substituted isotetronic acids from 2-acetamido-3-arylacrylates via vinylic C-H functionalization is reported. The reaction proceeds through heteroatom guided electrophilic insertion of nickel to the vinylic double bond followed by annulation with dibromomethane. This unconventional route features cascade steps, sole product formation, multiple functional group tolerance, low cost of catalysts and reagents, and readily available starting materials.
View Article and Find Full Text PDFWater enables an asymmetric cross reaction of α-keto acids with α-keto esters for the synthesis of quaternary isotetronic acids.
Chem Commun (Camb)
November 2019
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, P. R. China.
A water promoted asymmetric aldol/lactonization/enolization cascade reaction of α-keto acids and α-keto esters was developed, affording the first general protocol for the construction of chiral quaternary isotetronic acids with excellent enantioselectivity. Theoretical results indicate that intramolecular ionized enamine intermediates stabilized by water generate zwitterionic transition states in a lower activation energy and higher face selectivity, resulting in high activity and chemo- and enantioselectivity.
View Article and Find Full Text PDFIsotetronic acids from an oxidative cyclization.
Chem Commun (Camb)
July 2015
Chemistry Department, University of Hawaii at Manoa, 2545 The Mall, Honolulu, HI 96822, USA.
Oxidation of α,β-unsaturated methyl ketones with selenium dioxide leads to a cascade of reactions culminating in the formation of isotetronic acids.
View Article and Find Full Text PDFFacile synthesis of chiral spirooxindole-based isotetronic acids and 5-1H-pyrrol-2-ones through cascade reactions with bifunctional organocatalysts.
Chemistry
July 2014
State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, 116023 (China).
Unprecedented organocatalyzed asymmetric cascade reactions have been developed for the facile synthesis of chiral spirooxindole-based isotetronic acids and 5-1H-pyrrol-2-ones.The asymmetric 1,2-addition reactions of α-ketoesters to isatins and imines by using an acid-base bifunctional 6'-OH cinchona alkaloid catalyst, followed by cyclization and enolization of the resulting adducts, gave chiral spiroisotetronic acids and 5-1H-pyrrol-2-ones, respectively, in excellent optical purities (up to 98 % ee). FT-IR analysis supported the existence of hydrogen-bonding interaction between the 6'-OH group of the cinchona catalyst and an isatin carbonyl group, an interaction that might be crucial for catalyst activity and stereocontrol.
View Article and Find Full Text PDFOrganocatalyzed aldol reaction between pyridine-2-carbaldehydes and α-ketoacids: a straightforward route towards indolizidines and isotetronic acids.
Chemistry
October 2013
Université de Bordeaux, Institut des Sciences Moléculaires, UMR-CNRS 5255, 351, cours de la liberation, 33405 Talence Cedex (France), Fax: (+33) 540006286.
Enantioselective aldol reactions between substituted pyridine carbaldehydes and α-ketoacids were shown to provide isotetronic acids or their corresponding pyridinium salts, depending on the nature of the substituents on the pyridine ring. The pyridinium salts were generated through nucleophilic attack of the pyridine nitrogen atom onto the reactive keto functional group. Moderate-to-good yields of both compounds were typically obtained and high levels of enantioselectivity were observed by using benzimidazole pyrrolidine I as a catalyst.
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