Development of Unprecedented Hofmann Rearrangement of Sulfonamides

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We have developed the first example of Hofmann rearrangement of primary arenesulfonamides, which relies on the use of difluorobromane and affords N-arylsulfamoyl fluorides selectively. Reaction of the difluorobromane with p-toluenesulfonamide in benzene produced sulfamoyl fluoride in a high yield, through Hofmann rearrangement. Arenesulfonamides with electron-donating and-withdrawing substituents efficiently undergoes Hofmann rearrangement. The structure of N-p-tolylsulfamoyl fluoride was determined by a single-crystal X-ray analysis. The results obtained from the reaction of 2, 3, 5, 6-tetramethylbenzenesulfonamide strongly suggest that generation of sulfonyl nitrene will not be involved in this rearrangement.