Reaction of 15 (0.2 g in 1 ml of DMSO-de) with 1 equiv of potassium ieri-butoxide was observed directly by nmr. The AB pattern of the benzylic protons disappeared rapidly but there was no significant change in the chemical shift of the vinylic, SCH3, or OCHg resonances of 15. Attempts to isolate the product(s) of this reaction led only to the isolation of a sticky red solid which could not be recrystallized. Reaction of 15 with sodium hydride in dry THF in an inert atmosphere led to the immediate evolution of hydrogen, precipitation of NaBF4, and formation of a dark red solution which, after evaporating at reduced pressure, gave a red oil which solidified on washing repeatedly with pentane. Analysis by tic showed the presence of at least three components. Separation was unsuccessful, and the nmr of the crude product in CDC13 gave very broad signals which were uninformative as to structure.S-Benzyl-S-methyl-S-phenacylsulfonium ylide ( 14) was prepared from the corresponding sulfonium bromide salt by treatment with sodium hydride in THF.84 The sulfonium bromide was prepared from benzyl methyl sulfide and phenacyl bromide in benzene.Preparation of Sulfonium Salts 20.-Each of the salts was prepared from the corresponding sulfide by methylation with trimethyloxonium fluoroborate, as described above for 10. The salts so obtained were recrystallized to analytical purity from absolute ethanol. The sulfides were in turn prepared by the reaction of the appropriate thiophenol under basic conditions (sodium ethoxide in ethanol) with the appropriate phenacyl (24) K. W.

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The monoethyl ester of oxalacetic acid was synthesized and its rate of decarboxylation studied. While the rate of decarboxylation of un-ionized monoethyl oxalacetate is not affected by a change in the solvent polarity, the rate of decarboxylation of its anion is facilitated by a lowering of the polarity of solvents. In contrast to the decarboxylation of the un-ionized monoester which exhibits the kinetic deuterium isotope effect, the decarboxylation of its anion is insensitive to the deuterium isotope. Reaction mechanisms consistent with experimental results are proposed for the decarboxylation of the un-ionized and anionic oxalacetates.

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