title: Catalytic conjugate additions of carbonyl anions under neutral aqueous conditions.
abstract: The conjugate addition of carbonyl anions catalyzed by thiazolium salts that is fully operative under neutral aqueous conditions has been accomplished. The combination of alpha-keto carboxylates and thiazolium-derived zwitterions produces reactive carbonyl anions in a buffered protic environment that readily undergo conjugate additions to substituted alpha,beta-unsaturated 2-acyl imidazoles. The scope of the reaction has been examined and found to accommodate various alpha-keto carboxylates and beta-aryl substituted unsaturated 2-acyl imidazoles. The optimal precatalyst for this process is the commercially available thiazolium salt 5, a simple analogue of thiamin diphosphate. In this process, no benzoin products from carbonyl anion dimerization are observed. The corresponding 1,4-dicarbonyl compounds can be efficiently converted into esters and amides by way of activation of the N-methylimidazole ring via alkylation.
authors.affiliation: Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Myers
authors.forename: Ashwin R
authors.initials: AR
authors.lastname: Bharadwaj
authors.forename: Benjamin C
authors.initials: BC
authors.lastname: Milgram
authors.forename: Karl A
authors.initials: KA
authors.lastname: Scheidt
mesh_terms: D000478:Alkylation; D000838:Anions / Q000737:chemistry; D002264:Carboxylic Acids / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D015394:Molecular Structure; D010084:Oxidation-Reduction; D013844:Thiazoles / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D000838:Anions; D002264:Carboxylic Acids; D013844:Thiazoles; D014867:Water