Sulfonamides with lead reagents

Among chemical methods for the separation of amines, those of Hinsberg (reaction with / -toluenesulfonyl chloride) and of Alexander (94) (reaction with 3-nitrophthalic anhydride) are most commonly used. Tertiary amines do not react with the reagents mentioned and they can be separated after the reaction — for example, by extraction. Derivatives of primary amines with p-toluenesulfonyl chloride are soluble in alkali hydroxide solutions, in contrast to sulfonamides of secondary amines this is utilized for their separation. When primary and secondary amines are separated by reacting them with 3-nitrophthalic anhydride, use is made of the fact that only phthal-imine acids derived from primary amines can be cyclized. Practical utilization of both procedures is demonstrated by the separated of a mixture of aniline, ethylaniline, and diethylaniline. However, it should be mentioned that in a number of cases the procedures fail or do not lead to a sufficiently sharp separation. Negatively substituted amines which do not react with / -toluenesulfonyl chloride can be separated with 3-nitrophthalic anhydride. Some p-toluenesulfonamides of primary amines are poorly soluble in alkali. The derivative of primary amine with 3-nitrophthalic anhydride is cyclized merely by boiling in benzene, and the phthalimide formed is soluble in benzene and can be isolated together with the tertiary amine. 

A number of alkylation products from MeOTf and heterocycles have been advocated as useful intermediates. Thus treatment of 2-substituted thiazoles with MeOTf in acetonitrile, followed by reduction of the salt formed with sodium borohydride/CuO in CH2CI2, leads to aldehydes. l-(Benzenesulfonyl)-3-methylimidazolium and l-(/>-toluenesulfonyl)-3-inethylimidaz-olium triflates have been proposed as efficient reagents for the preparation of aryl sulfonamides and aryl sulfonates. MeOTf alkylates 2,5-oxazoles to give salts which can be reduced by PhSiHs/CsP to give 4-oxazolines, and these provide a route to stabilized azomethine ylides. ... 

The difficult access to nitrosoarenes and their tendency to dimerize makes these reagents less attractive. The substitution of the nitroso group with a toluene-sulfonamide leads to aryl 4-tolylazo sulfones of type 306, which can be used as... 

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