Chlorosulfonation, anisole

It thermally decomposes to A -dimethylcarbamoyl chloride. Secondary formamides form similar adducts, which on heating afford isocyanates. Aromatic compounds such as anisole are not foimylated by the DMF-SO2CI2 adduct but chlorosulfonated. This reaction was also performed with thiophenes 2-thiophenecarbaldehydes are formed as byproducts. The formation of triformaminomethane from form-amide and SO2CI2 has been reported. ... 

Anisole (methyl phenyl ether) is extremely reactive towards sulfonation due to the presence of the strongly electron-donating (-fM) methoxy group. It therefore reacts with chlorosulfonic acid (two equivalents) at 0 °C to give mainly p-methoxybenzenesulfonyl chloride. With chlorobenzene, the chlorine atom exerts a strong electron-withdrawing (-1 effect) so sulfonation will be rather less easy than for benzene. Treatment of chlorobenzene with chlorosulfonic acid (four equivalents) at 25 C (3 hours) afforded p-chlorobenzenesulfonyl chloride (84%) and di(/7-chlorophenyl sulfone) (6%)." Chlorobenzene with chlorosulfonic acid (six equivalents) at 150-160 °C (8 hours) gave the 2,4-disulfonyl chloride. 

Anisole (methyl phenyl ether or methoxybenzene (187 Ar = Ph, R = Me)) reacts with chlorosulfonic acid (two equivalents) in chloroform at 0 °C to give 4-methoxybenzenesulfonyl chloride the latter was also obtained by treatment of 187 with a mixture of chlorosulfonic acid and sulfuric acid at 10 The chlorosulfonation of o- 189 and p- 190 substituted anisoles by chlorosulfonic acid was also achieved in high yields. The o-isomers 189 generally only required mild conditions e.g. a few minutes at 0 C) the ease of chlorosulfonation is probably due to the lack of steric hindrance in the reactive 4-position. 

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