Vinylsulfone acceptors

Vinylsulfone acceptors A conjugate addition of aldehydes (203) to l,3-bis(sulfonyl) butadienes (202), catalysed by the Jprgensen-Hayashi prolinol derivative (123a), followed by cyclization, has been reported to produce cyclohexadiene derivatives (204) with <95% ee. The reaction is assumed to proceed via the usual enamine... 

Nevertheless, Michael acceptors such as phenyl vinylsulfone, ethyl cinna-mate, methyl acrylate, acrylonitrile and a, 3-unsaturated aldehydes failed to react in the reaction catalyzed by Yb(OTf)3 3H2O. 

Vinylsulfones have also been used as Michael acceptors suitable to be activated by H-bonding interactions with a cinchone-type catalyst. In particular. 

The stereoelectronic effects of alkyne additions are not limited to anions, as radicals react similarly. The sulfonyl radical adds regio- and stereoselectively to the terminal carbon, giving the E-bromo vinylsulfone. NBO analysis shows that the radical center can act as both a donor and acceptor in interactions with the antiperiplanar C-S bond. In the radical intermediate formed by addition of tosyl radical to 1-hexyne, the donor character dominates. The energy of the n- CT was larger than the (Tj, g n (-27 vs. 7 kcal/mol, for the sum of a and p-spins. Figure 7.47). ... 

Vinylsulfonates RCH=CHS03Ph, sulfonamides, and their congeners are another class of electrophilic acceptors, where / -arylation with ArB(OH)2 has been attained. Thus, the Rh complex with (522) as the chiral ligand, catalysed the reaction in aqueous dioxane with K3PO4 present at 60 C to give RArCH-CH2S03Ph with >95% ee ... 

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