Methylsulfonate groups

Japanese workers have also displaced a methyl sulfone group with a variety of nucleophiles. Thus they were able to introduce, ethoxy, thiophenyl, aniline, and malonic acid groups in to the pyridine A -oxide derivative (105). Acid hydrolysis produced the 2-one compound, while reduction with sodium borohydride cleaved off the methylsulfone group <87CPB1030>. 

FIGURE 16.3 Chemical structures of chloramphenicol and thiamphenicol. Thiamphenicol, in which the nitroso group of chloramphenicol is replaced by a methylsulfone group, retains antibiotic activity, but does not cause the aplastic anemia that is a major concern with chloramphenicol therapy. 

In experiment 1, the perprotio-sulfonyl anion [H6]-A reacts to form the methylated per-protio-sulfone [H6]-B. It is not known whether this is the result of an intra- or an intermolecu-lar SN reaction. In experiment 2 of Figure 2.6, the sulfonyl anion [D6]-A, which is perdeuter-ated in both methyl groups, reacts to form the hexadeuterated methylsulfone [D6]-B. Even this result does not clarify whether the methylation is intra- or intermolecular. An explanation is not provided until the third experiment in Figure 2.6, a so-called crossover experiment. 

Pd complexed with 2-pyridyldiphenylphosphine (or its 6-methylpyridyl derivative) and weakly coordinating counter ions, such as methylsulfonate, are employed as catalyst [84, 85]. After the coordination of methanol and CO the migration of the methoxy group takes place to form the palladium carbomethoxy species. Then the coordination of propyne takes place. The steric bulk of the pyridyl group, and in particular of the 6-methylpyridyl group, induces the con-... 

Cyclopropylaziridine moieties in a polycyclic system have been formed by intramolecular attack of an amide moiety and substitution of a p-toluenesulfonate, " methylsulfonate, hydroxy, " or carboxylate " group a to a cyclopropane ring. The yields are generally excellent. 

Sulfonylation involves the replacement of a hydrogen atom by the sulfonyl (RSO2) group. The early work on the chemistry of sulfones was reported by Suter and the mechanism of sulfonylation has been reviewed by Taylor. In sulfonylation, the reaction is catalysed by Lewis acids and aluminium chloride is usually the favoured catalyst since the relative activities of the catalysts in methylsulfonation are as depicted (Figure 2). ... 

In Equation 149, the chlorosulfonation occurs, as expected, in the / ara-position relative to the electron-donating (-f I) methylene moiety and simultaneously the three chlorine atoms attached to the silicon atom are sequentially substituted by chlorosulfonate and methoxy groups to give the methylsulfonate 470. In this context, it is well known ° that chlorosilanes react with chlorosulfonic acid to yield the corresponding chlorosulfonate esters, as occurs in the first stage of the conversion shown (Equation 149). 

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