title: Catalytic, enantioselective [4 + 2]-cycloadditions of ketene enolates and o-quinones: efficient entry to chiral, alpha-oxygenated carboxylic acid derivatives.
abstract: We report catalytic, enantioselective [4 + 2]-cycloadditions of o-quinones with ketene enolates (derived from readily available acid chlorides) using cinchona alkaloid derivatives as catalysts to produce products in high enantiomeric excess (ee) and good to excellent yields. The thermodynamic driving force for these reactions is due in part to the restoration of aromaticity to the products. The resulting chiral, bicycloadducts can be synthetically manipulated in a variety of useful ways, for example to provide a flexible synthesis of alpha-oxygenated carboxylic acid derivatives.
authors.affiliation: Department of Chemistry, New Chemistry Building, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA.
authors.forename: Tefsit
authors.initials: T
authors.lastname: Bekele
authors.forename: Meha H
authors.initials: MH
authors.lastname: Shah
authors.forename: Jamison
authors.initials: J
authors.lastname: Wolfer
authors.forename: Ciby J
authors.initials: CJ
authors.lastname: Abraham
authors.forename: Anthony
authors.initials: A
authors.lastname: Weatherwax
authors.forename: Thomas
authors.initials: T
authors.lastname: Lectka
mesh_terms: D002264:Carboxylic Acids / Q000138:chemical synthesis*; D002384:Catalysis; D002703:Chloranil / Q000031:analogs & derivatives / Q000737:chemistry; D003500:Cyclization; D005030:Ethylenes / Q000737:chemistry*; D007659:Ketones / Q000737:chemistry*; D010084:Oxidation-Reduction; D011809:Quinones / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D002264:Carboxylic Acids; D005030:Ethylenes; D007659:Ketones; D011809:Quinones; D002703:Chloranil; C008223:ketene