title: Organocatalytic asymmetric conjugate addition of 3-monosubstituted oxindoles to (E)-1,4-diaryl-2-buten-1,4-diones: a strategy for the indirect enantioselective furanylation and pyrrolylation of 3-alkyloxindoles.
abstract: An asymmetric conjugate addition of 3-monosubstituted oxindoles to a range of (E)-1,4-diaryl-2-buten-1,4-diones, catalyzed by commercially available cinchonine, is described. This organocatalytic asymmetric reaction affords a broad range of 3,3'-disubstituted oxindoles that contain a 1,4-dicarbonyl moiety and vicinal quaternary and tertiary stereogenic centers in high-to-excellent yields (up to 98%), with excellent diastereomeric and moderate-to-high enantiomeric ratios (up to 99:1 and 95:5, respectively). Subsequently, cyclization of the 1,4-dicarbonyl moiety in the resultant Michael adducts under different Paal-Knorr conditions results in two new kinds of 3,3'-disubstituted oxindoles--3-furanyl- and 3-pyrrolyl-3-alkyl-oxindoles--in high yields and good enantioselectivities. Notably, the studies presented here sufficiently confirm that this two-step strategy of sequential conjugate addition/Paal-Knorr cyclization is not only an attractive method for the indirect enantioselective heteroarylation of 3-alkyloxindoles, but also opens up new avenues toward asymmetric synthesis of structurally diverse 3,3'-disubstituted oxindole derivatives.
authors.affiliation: National Engineering Research Center of Chiral Drugs, Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041, P.R. China.
authors.forename: Yu-Hua
authors.initials: YH
authors.lastname: Liao
authors.forename: Xiong-Li
authors.initials: XL
authors.lastname: Liu
authors.forename: Zhi-Jun
authors.initials: ZJ
authors.lastname: Wu
authors.forename: Xi-Lin
authors.initials: XL
authors.lastname: Du
authors.forename: Xiao-Mei
authors.initials: XM
authors.lastname: Zhang
authors.forename: Wei-Cheng
authors.initials: WC
authors.lastname: Yuan
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D002384:Catalysis; D002930:Cinchona Alkaloids / Q000737:chemistry*; D003500:Cyclization; D007211:Indoles / Q000737:chemistry*; D015394:Molecular Structure; D000078183:Oxindoles; D013237:Stereoisomerism
chemical_list: D000475:Alkenes; D002930:Cinchona Alkaloids; D007211:Indoles; D000078183:Oxindoles; C022960:2-oxindole; C558934:butylene; C010086:cinchonine