DEVELOPMENT AND SYNTHETIC APPLICATION FOR STEREOSELECTIVE MICHAEL/ALDOL TANDEM REACTION TRIGGERED BY THIOLATE ANION

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The titled reaction, the Michael/aldol tandem reaction, was investigated and found the following developments.1) We found this reaction can be applied to not only unsaturated esters but also unsaturated amides. Use of the procedure makes it easy to prepare amide-Baylis-Hillman adducts, which was difficult to synthesize under classical Baylis-Hillman reaction conditions. It should be mentioned that our reaction condition requires no special protection for the acidic amide NH proton for the progress of aldol reaction.2) Use of magnesium ion as a counter cation of thiolate opens the new aspect of the reaction that shows opposite diastereoselectivity for the aldol reaction. Under these conditions, anti-aldols, the preparation of which are recognized to be limited. We have also attempted to catch the reaction intermediate to understand the reaction mechanism, and found that a-thioalkoxide is the intermediate of the reaction.3) We have developed a new ready method to prepare multi-substituted tetrahydrofurans through the present method.4) Regiochemistry of radical elimination reaction was investigated. The regioselective transformation of the tandem adducts to α, β-unsaturated or β, γ-unsaturated ester was accomplished. This result is the first example of the regiocontrol in the radical elimination reaction.5) We have accomplished the first regiocontrol of the tandem or the Michael reaction of thiol to unsymmetrically substituted fumaric ester.