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ABSTRACT: An efficient protocol for direct catalytic alkynylation of ketoimines is described. The simultaneous activation of a soft Lewis basic terminal alkyne and a ketoimine bearing a thiophosphinoyl group by soft Lewis acid Cu(I) is crucial for high conversion. The reaction can be rendered asymmetric with a chiral bisphosphine ligand (S,S)-Ph-BPE.
Organic Letters 01/2013; · 5.86 Impact Factor
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ABSTRACT: Catalytic asymmetric conjugate addition of nitroalkanes to α,β-unsaturated thioamides is promoted by a mesitylcopper/(R)-DTBM-Segphos precatalyst, affording γ-nitrothioamides in moderate to high syn-selectivity and excellent enantioselectivity. The intermediate Cu-thioamide enolate functions as a soft Lewis acid/hard Brønsted base cooperative catalyst to drive the catalytic cycle efficiently under proton transfer conditions.
Organic Letters 11/2011; 14(1):110-3. · 5.86 Impact Factor
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Chemistry - An Asian Journal 11/2010; 5(11):2351-4. · 4.50 Impact Factor
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ABSTRACT: A highly enantioselective catalytic asymmetric access to 3-aminooxindoles with a tetrasubstituted carbon stereocenter is described. 1-2 mol % of homobimetallic (R)-Ni(2)-Schiff base 1 catalyzed the asymmetric amination of 3-substituted oxindoles with azodicarboxylates to give (R)-products in 99-89% yield and 99-87% ee. Reversal of enantiofacial selectivity was observed between bimetallic and monometallic Schiff base complexes, and monometallic (R)-Ni-Schiff base 2c gave (S)-products in 98-80% ee. Transformation of the products into an optically active oxindole with a spiro-beta-lactam unit and a known key intermediate for AG-041R synthesis is also described.
Journal of the American Chemical Society 02/2010; 132(4):1255-7. · 9.91 Impact Factor
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ABSTRACT: A homodinuclear Ni(2)-Schiff base 1 complex (0.1-1 mol%) promoted the direct catalytic asymmetric aldol reaction of beta-keto esters with formaldehyde, giving hydroxymethylated adducts in 94-66% ee.
Chemical Communications 09/2009; · 6.17 Impact Factor