Phenylmethanesulfonyl chloride

That there is also considerable carbanion character on the carbon adjacent to the sulfonyl group in the rate-determining transition state for sulfene formation from phenylmethanesulfonyl chlorides is shown (King and Lee, 1969) by the fact that p for sulfene formation from ArCH2S02Cl and pyridine is +2.3, with the rates being better correlated by a - rather than o-values. 

However, King et al. (1977) have shown that in some cases one can get abnormal addition and the formation of substituted sulfinic acids (Scheme 4). Abnormal addition, for example, is involved as the first step in the complex pathway (207) by which sulfine [90] is formed from PhCH=S02 when phenylmethanesulfonyl chloride is treated with a tertiary amine in the absence of any of the normal sulfene-trapping reagents (King and Harding, 1976). 

Good yields for the 3-aminothietane 1,1-dioxides can be expected by the reaction of phenylmethanesulfonyl chloride with rrans-/S-dimethylamino-styrene in the presence of triethylamine. Reaction proceeds by the pathway given in Scheme 1. 

The reaction of epoxy sulfonyl chlorides 136 with triethylamine is thought to proceed through intermediate epoxy sulfenes 137 to give the 5/7-1,2-oxathiole 2,2-dioxides 138 (Equation 26) <1998SL1411>. The interaction of phenylmethanesulfonyl chloride with triethylamine, 2,4,6-trimethylpyridine A -oxide, and an alkene probably involves epoxidation of phenylsulfene to give the hitherto unknown oxathiirane 3, 3 -dioxide (a-sultone) 139 which then adds to the alkene to afford the products 140 (Scheme 6) <2000CC189>. 

Sulfenes are very reactive and occur as intermediates in several synthetically important reactions (see p. 115).3b They have not been isolated and are formed by base-induced eliminations for instance, a sulfene is formed in the reaction of a sulfonyl chloride containing at least one a-hydrogen atom with a tertiary amine. As an illustration, when phenylmethanesulfonyl chloride (97) is treated with pyridine, phenylsulfene (98) is formed as a transient species (Scheme 65). 

A further variation in mechanism is found with methanesulfonyl chloride and p-toluidine. The reaction with triethylamine goes via the sulfene, but with pyridine by a direct displacement88, perhaps involving general base catalysis. The key variable in this case would appear to be the basicity of the amine with A-ethylmorpholine (pKa 7.7) the sulfene route predominated (< 87%) but with iV-methylimidazole (pKa 6.95) it was the minor pathway ( 20%). Phenylmethanesulfonyl chloride, it may be noted, reacts by the sulfene pathway with either pyridine or triethylamine and p-toluidine88. 

Sulfene trapping competition experiments have been carried out with a series of aromatic amines132. In each case phenylsulfene was formed from phenylmethanesulfonyl chloride with triethylamine in the presence of an equimolar mixture of p-toluidine and another aniline derivative. The product ratio ( X-anilide p-toluidide) varied from 1.12 for p-anisidine to 0.12 for m-nitroaniline, and gave a good fit to a Hammett plot with cr = — 1.04 this accords with a transition state possessing a partial positive charge in the aromatic amine. 

In principle, / -diketones may react at the enolic hydroxyl or the a-carbon in practice, in two examples studied both modes of reaction were seen91. Dimedone with phenylmethanesulfonyl chloride and triethylamine yielded the sulfonic ester of the enol, while dibenzoylmethane gave quantitative conversion to the sulfone, (PhC0)2CHS02CH2Ph91. 

Thermal loss of sulfur dioxide, i.e. desulfonylation to form a carbene and sulfur dioxide, was originally put forward by Wedekind and Schenk in 1911 to explain the formation of stilbene in the reaction of phenylmethanesulfonyl chloride with triethylamine5. As we have already recounted, another mechanism is much more likely for that transformation, but... 

Kinetic studies of the solvolysis of phenylmethanesulfonyl chloride (PhCH2S02Cl) in a wide range of solvent mixtures at 308 K were reported. Since an extended Grunwald-Winstein plot was linear and a kinetic solvent isotope effect of 2.34 was seen for MeOH/MeOD, a dissociative S 2 mechanism was indicated. ... 

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