Asymmetric organocatalysis conjugate addition reactions

The Conjugate Addition Reaction a Very Convenient Platform for Asymmetric Organocatalysis... 

Carbons and Carbon Supported Catalysts in Hydroprocessing 2 Chiral Sulfur Ligands Asymmetric Catalysis 3 Recent Developments in Asymmetric Organocatalysis 4 Catalysis in the Refining of Fischer-Tropsch Syncrude 5 Organocatalytic Enantioselective Conjugate Addition Reactions A Powerful Tool for the Stereocontrolled Synthesis of Complex Molecules... 

A decade has now passed since the studies of my laboratory and those of David MacMillan s refocused the considerable attention of the conununity on the profound potential of small organic molecules to catalyze asymmetric reactions. In this time, the scope of organocatalysis has enlarged considerably with respect both to the type of reactions catalyzed (aldol, cycloaddition, redox, asymmetric assembly and domino reactions, conjugate addition reactions, etc.) and the mechanisms used... 

Michael-aldol reaction as an alternative to the Morita-Baylis-Hillman reaction 14 recent results in conjugate addition of nitroalkanes to electron-poor alkenes 15 asymmetric cyclopropanation of chiral (l-phosphoryl)vinyl sulfoxides 16 synthetic methodology using tertiary phosphines as nucleophilic catalysts in combination with allenoates or 2-alkynoates 17 recent advances in the transition metal-catalysed asymmetric hydrosilylation of ketones, imines, and electrophilic C=C bonds 18 Michael additions catalysed by transition metals and lanthanide species 19 recent progress in asymmetric organocatalysis, including the aldol reaction, Mannich reaction, Michael addition, cycloadditions, allylation, epoxidation, and phase-transfer catalysis 20 and nucleophilic phosphine organocatalysis.21... 

Lately, sulfones have become especially important substrates in organocatalysis [87]. First studies on the asymmetric conjugate addition of aldehydes to vinyl sulfones were carried out by Alexakis and Mossd employing as catalyst bipyrrolidine 30 (25 mol%) for the addition of linear and a-branched aldehydes to l,l-bis(benzenesulfonyl)ethylene [88], Large excess of aldehyde (10 equivalents) was required and moderate levels of enantioselection were obtained for linear aldehydes (53-80% ee), while reactions with a-branched nucleophiles led to racemic or very low selectivities (0-12% ee). With respect to the mechanism, the acyclic synclinal model proposed by Seebach and GoUnski [70] involving a trans enamine intermediate was postulated. 

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