Difluoro-lambda3-bromane-induced Hofmann rearrangement of sulfonamides: synthesis of sulfamoyl fluorides.
We report the first example of Hofmann rearrangement of primary arenesulfonamides, which relies on the use of p-trifluoromethylphenyl(difluoro)-lambda(3)-bromane and affords N-arylsulfamoyl fluorides selectively at room temperature. Reaction of aryl-lambda(3)-iodanes with p-toluenesulfonamide affords sulfonylimono-lambda(3)-iodanes, being excellent progenitors for generation of metal-nitrenoid species. In marked contrast, reaction of the difluoro-lambda(3)-bromane with p-toluenesulfonamide in benzene produced unique N-p-tolylsulfamoyl fluoride in a high yield, through Hofmann rearrangement. Arenesulfonamides with electron-donating (p-MeO and o-Me) and -withdrawing substituents (p-F, p-Cl, and p-CF(3)) efficiently undergoes the lambda(3)-bromane-induced Hofmann rearrangement. The structure of N-p-tolylsulfamoyl fluoride was determined by a single-crystal X-ray analysis. The differences in nucleofugality between aryl-lambda(3)-iodanyl and aryl-lambda(3)-bromanyl groups, the later being greater, probably play a pivotal role in determining the reaction course. 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.
Ochiai
Masahito
M
Graduate School of Pharmaceutical Sciences, University of Tokushima, 1-78 Shomachi, Tokushima 770-8505, Japan. mochiai@ph.tokushima-u.ac.jp
Okada
Takuya
T
Tada
Norihiro
N
Yoshimura
Akira
A
Miyamoto
Kazunori
K
Shiro
Motoo
M
D018360:Crystallography, X-Ray; D006842:Hydrocarbons, Brominated / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013449:Sulfonamides / Q000138:chemical synthesis / Q000737:chemistry*
D006842:Hydrocarbons, Brominated; D013449:Sulfonamides; C528824:p-trifluoromethylphenyl(difluoro)-lambda3-bromane