0,7-Unsaturated methyl sulfinates

Unsaturated ketones, 211-212 a,S-Unsaturated 7-lactones, 200 0,7-Unsaturated methyl sulfinates, 381 a,0-Unsaturated nitriles, 351, 394, 535 0,7-Unsaturated nitriles, 84 a,0-Unsaturated sulfones, 42-43, 436 c ,(3-Unsatutated sulfoxides, 193, 394 a,0-Unsaturated tosylhydrazones, 537 ff, 7-Unsaturated-6 -valerolactones, 188 Uracil, 639, 640... 

Ene reactions. The antimony pentafluoride—methyl fluoride complex in SO2 undergoes the ene reaction with vinyl halides (1) at -65 to give unsaturated methyl sulfinates (2), isolated after addition of methanol. Yields... 

SO2 Activation. At low temperatures, l-alkoxy-l,3-dienes add to sulfur dioxide activated by TBDMS triflate to generate a zwitterionic intermediate that can be quenched with silyl enol ethers to give, y-unsaturated silyl sulfinates. DesUylation and reaction with methyl iodide provide a stereoselective route to polyfunctional sulfones in an overall four-component coupling sequence (eq 50). ... 

Equation 54 describes the preparation of dienes by a similar cyclopropane cleavage followed by proton transfer and elimination of sulfinate. The weak donor ability of a (trimethylsilyl)methyl group also assists Lewis acid-promoted ring cleavage according to equation 55, which allows synthesis of y, -unsaturated ketones Interestingly, the related ester opens smoothly only if fluoride reagents are employed (equation 56) ... 

The room temperature treatment of a series of 1-alkenyl 2-(trime-thylsilyl)ethyl sulfones leads to an intermediate o , 8-unsaturated sulfinate anion which can be methylated at sulfur to produce methyl sulfones in 54-83% (eq 12). If alkyl hydrogens are attached at a position y to the sulfonyl groups, undesirable double bond migration may occur. Although not specifically demonstrated, alkylation with other electrophiles may be possible, as shown for arenesulfinate anions. ... 

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