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ABSTRACT: Amine-catalyzed [2 + 2 + 2] and [2 + 4] annulations of Morita-Baylis-Hillman (MBH) acetates with cyano activated alkenes and 1,3-azadienes have been developed to provide cyclohexanes and tetrahydropyridines. In the annulations, MBH acetates serve as a novel C2 component with an inactive homoallylic methyl involved in the bond formation.
Chemical Communications 03/2013; · 6.17 Impact Factor
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ABSTRACT: An amine-catalyzed [4 + 2] annulation of Morita-Baylis-Hillman allylic acetates 2 with electron-deficient alkenes or diazenes has been developed for efficient syntheses of highly functionalized cyclohexenes, tetrahydropyridazines, and important spirocycles. This reaction unveils a new reactivity pattern of the intensely studied allylic compounds 2 acting as a C(4) synthon in Lewis base catalyzed annulation reactions and also showcases divergent catalysis between tertiary amines and phosphines.
Organic Letters 02/2012; 14(4):996-9. · 5.86 Impact Factor
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ABSTRACT: A highly stereoselective PBu(3)-mediated vinylogous Wittig olefination between α-methyl allenoates and a variety of aldehydes is presented as the first example of a practical and synthetically useful vinylogous Wittig reaction. Mechanistic experiments including deuterium-labeling, intermediate entrapment, and NMR monitoring have been deliberately conducted. On the basis of mechanistic investigations, a reliable mechanism for the vinylogous Wittig reaction is proposed, which features a water/phosphine-coassisted allylic phosphorus ylide 1,3-rearrangement pathway, rather than previous retro-Diels-Alder ones. It is noteworthy that mechanistic findings in this work also provide supportive evidence for typical mechanisms of important phosphine-mediated reactions of allenoates.
The Journal of Organic Chemistry 08/2011; 76(18):7528-38. · 4.45 Impact Factor
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ABSTRACT: Phosphine-mediated olefination between alpha-substituted allenoates and aldehydes to form 1,2,3,4-tetrasubstituted 1,3-dienes is presented. High levels of chemo- and diastereoselectivity and yield are obtained for a wide scope of substrates with the choice of appropriate phosphines. This reaction evidences the capacity of phosphines in the control of reaction pathways and provides a highly efficient synthetic method for tetrasubstituted conjugated dienes.
Organic Letters 08/2010; 12(15):3556-9. · 5.86 Impact Factor
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ABSTRACT: A novel phosphine-mediated reductive cyclopropanation between alpha-substituted allenoates 2 and aldehydes 1 is described. It represents a new member of the allene-based annulations, which provides facile and efficient access to highly functionalized cyclopropanes 3 from simple and readily available starting materials. It also unveils an unprecedented reactivity pattern of allenoates with aldehydes.
Organic Letters 02/2010; 12(3):544-7. · 5.86 Impact Factor
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Chemistry 09/2009; 15(35):8698-702. · 5.93 Impact Factor
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ABSTRACT: The phosphine-mediated olefination of aldehydes with electron-deficient allenes to afford trisubstituted conjugated dienes in fair to excellent yields with high E-selectivity is described. The reaction represents a new reactivity pattern of allenes with aldehydes and also provides a highly stereoselective synthetic method for preparing conjugated dienes. In the reaction, the phosphine acts as a nucleophilic promoter to generate in situ an active phosphorus ylide which mediates the intermolecular olefination.
Organic Letters 08/2009; 11(15):3498-501. · 5.86 Impact Factor
