Carboxylic esters, aryl methyl, cleavage

Cleavage of esters, ethers, and lactones. The reagent resembles CsHaSLi (3, 188 5, 415) and CaHsSNa (4, 465) in reactivity for cleavage of hindered esters and methyl aryl ethers. In addition it cleaves lactones to methylthio carboxylic acids an example is the conversion of butyrolactone to CHGSCH2CH2CH2COOH in 69% yield. A direct comparison indicates that this reagent is superior to lithium thiophenoxide for cleavage of the lactone 1 to 2. 

Ester Dealkylation. Among the widest uses for TMS-I involves the mild cleavage of carboxylic esters under neutral conditions. The ester is treated with TMS-I to form an initial ox-onium intermediate which suffers attack by iodide (eq 5). The trimethylsilyl ester is cleaved with H2O during workup. Although the reaction is general and efficient, it is possible to accomplish selective cleavage according to the reactivity trend benzyl, r-butyl > methyl, ethyl, i-propyl. Neutral transesterification is also possible via the silyl ester intermediate. Aryl esters are not cleaved by TMS-1, however, since the mechanism involves... 

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