Phenylthiomethyl chlorides

We have just seen in a preceding scheme (see Section 4.2.1.5) an example of alkylation of a silylated enolate with phenylthiomethyl chloride. The Lewis acid-promoted phenylthioalkylation of O-silylated enolates of ketones, aldehydes, esters and lactones has been used by Paterson and Fleming as a convenient synthetic route to a-alkylated or alkylidenated carbonyl compounds [323-325] according to the accompanying scheme. 

Allylsilanes react with alkoxymethyl and phenylthiomethyl chlorides in the presence of Lewis acids (Scheme 53), and dithioacetals, similarly, where substantial stereoselection can be achieved with large aryl groups on the sulfur atoms (Scheme 54). Monothioacetals react selectively with cleavage of the carbon-sulfur bond when tin(IV) chloride is used as the Lewis acid (Scheme 55). ° ... 

Preparative Methods can be prepared from (phenylthiomethyl) triphenylphosphonium iodide and A,A(-dimethylmethylene ammonium chloride in refluxing acetonitrile (eq 1). ... 

Another new reagent for the protection of alcohols and phenols is 2-trimethyl-silylethoxymethyl chloride (67), said to be readily available. The derived SEM ethers (Scheme 30) are stable to acidic conditions that remove 2-tetrahy-dropyranyl, 2-tetrahydrofurfuryl, and trialkylsilyl groups, but can be cleaved by fluoride ion. Phenylthiomethyl ethers may be used in the protection of phenols. They have been reported as more resistant to hydrolysis than aliphatic or aromatic methylthiomethyl ethers, and are removed with mercuric chloride. 

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