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ABSTRACT: The first organocatalytic asymmetric Michael addition of 5H-oxazol-4-ones to nitroolefins has been developed. In the presence of easily prepared l-tert-leucine-derived tertiary amine/thiourea catalyst, the Michael addition of 5H-oxazol-4-ones to nitroolefins proceeded in an excellent diastereo- and enantioselective manner (up to 99% ee and >19:1 dr). The Michael adducts obtained are valuable precursors for the synthesis of chiral α-alkyl-α-hydroxy carboxylic acid derivatives, which represent a series of versatile building blocks in many biologically active compounds.
Organic Letters 05/2013; · 5.86 Impact Factor
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ABSTRACT: The asymmetric allylic alkylation of Morita-Baylis-Hillman (MBH) carbonates with allyl ketones has been developed. The alpha-regioselective alkylation adducts, containing a hexa-1,5-diene framework with important synthetic value, were achieved in up to 83% yield, >99% ee and 50:1 dr by using a commercially available Cinchona alkaloid as the catalyst. From the allylic alkylation adduct, cyclohexenes bearing two adjacent chiral centers were readily obtained.
The Journal of Organic Chemistry 04/2013; · 4.45 Impact Factor
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ABSTRACT: The γ-butenolide structural motif is a prominent feature in many bioactive natural products and drugs. This short review summarizes catalytic asymmetric synthesis of γ-butenolides through direct vinylogous reactions by metal complexes and organocatalysts. In light of building chiral γ-tertiary and quaternary carbon centers of butenolides, three synthetic strategies are included: 1) the reactions with furanone derivatives as nucleophiles, 2) olefination of γ,γ-disubstituted butenolides and 3) the reactions by using γ,γ-disubstituted butenolides as nucleophiles.
Mini Reviews in Medicinal Chemistry 04/2013; · 2.53 Impact Factor
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ABSTRACT: An organocatalytic asymmetric sulfenylation of 3-aryloxindoles with N-(sulfanyl)succinimides has been developed by using commercially available (DHQD)(2)PHAL as catalyst. Various chiral 3-benzylthio-, alkylthio-, and arylthio-substituted oxindoles, containing 3,3-disubstituted quarternary carbon stereocenters, could be obtained in high enantioselectivities (85-97% ee). Furthermore, the opposite enantiomers of the sulfenylated products were readily accessible with equal excellent enantioselectivities (86-95% ee) by replacing the catalyst with (DHQ)(2)PHAL.
Organic Letters 08/2012; 14(17):4670-3. · 5.86 Impact Factor
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ABSTRACT: The asymmetric allylic alkenylation of Morita-Baylis-Hillman (MBH) carbonates with N-itaconimides as nucleophiles has been developed using a commercially available Cinchona alkaloid catalyst. A variety of multifunctional chiral α-methylene-β-maleimide esters were attained in moderate to excellent yields (up to 99%) and good to excellent enantioselectivities (up to 91% ee). The origin of the regio- and stereoselectivity was verified by DFT methods. Calculated geometries and relative energies of various transition states strongly support the observed regio- and enantioselectivity.
The Journal of Organic Chemistry 07/2012; 77(15):6600-7. · 4.45 Impact Factor
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ABSTRACT: A Lewis base catalyzed allylic hydroxylation of Morita-Baylis-Hillman (MBH) carbonates has been developed. Various chiral MBH alcohols can be synthesized in high yields (up to 99%) and excellent enantioselectivities (up to 94% ee). This is the first report using water as a nucleophile in asymmetric organocatalysis. The nucleophilic role of water has been verified using (18)O-labeling experiments.
The Journal of Organic Chemistry 08/2011; 76(16):6894-900. · 4.45 Impact Factor
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ABSTRACT: Enanatiopure β-methyl-γ-monofluoromethyl alcohols were prepared from the allylic alkylation between fluorobis(phenylsulfonyl)methane with Morita-Baylis-Hillman carbonates. The reaction was catalyzed by using the Cinchona alkaloid derivative, (DHQD)(2)AQN. The origin of the stereoselectivity was verified by DFT methods. Calculated geometries and relative energies of various transition states strongly support the observed stereoselectivity.
Chemistry 06/2011; 17(29):8066-70. · 5.93 Impact Factor
