Michael additions trifluoromethanesulfonate

Keywords ethyl 2-oxo-cyclohexanecarboxylate, ethyl acrylate, Michael addition, trifluoromethanesulfonic acid... 

High enantioselectivities may be reached using the kinetic controlled Michael addition of achiral tin enolates, prepared in situ, to a,/i-unsaturated carbonyl compounds catalyzed by a chiral amine. The presence of trimethylsilyl trifluoromethanesulfonate as an activator is required in these reactions236. Some typical results, using stoichiometric amounts of chiral amine and various enolates are given below. In the case of the l-(melhylthio)-l-[(trimethylsilyl)thio]ethene it is proposed that metal exchange between the tin(II) trifluoromethanesulfonate and the ketene acetal occurs prior to the 1,4-addition237,395. 

Trifluoromethanesulfonic acid in the presence of anisole cleaves a number of protecting groups currently used in peptide chemistry without significant side reactions Tetraalkylammonium cyanides, which are soluble in organic solvents, catalyze Michael additions and other base-catalyzed reactions. As nucleophiles they are more powerful than NaCN . 

Catalytic amounts (5 mol%) of trityl chloride and tin(II) chloride, or antimony(V) chloride and tin(II) triflate, have also been used to promote the Michael additions, with stereoselectivity in favor of the anti isomers and slightly reduced ratios in comparison with the above results. No stereoselectivity was observed with catalytic amounts (10 mol %) of ytterbium(III) trifluoromethanesulfonate. ... 

Aluminum trifluoromethanesulfonate has proved to act as a mild catalyst for the Michael addition of 0-silylated ketene acetals with a./S-unsaturated esters (eq 14). A few glutarates were obtained in good yields using this method. ... 

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