The Reaction of Primary Nitro Compounds with Dipolarophiles in the Presence of p-Toluenesulfonic Acid

Abstract 3-Substituted 2-isoxazolines or isoxazoles were obtained from the reaction of primary nitro compounds [methyl nitroacetate, 2-nitro-1-phenylethanone, (nitromethyl)benzene, 1-nitropropane, and (phenylsulfonyl)nitromethane] with dipolarophiles in refluxing mesitylene in the presence of a small amount of p-toluenesulfonic acid. The formation of these products can be explained in terms of 1,3-dipolar cycloaddition of nitrile oxide generated by a dehydration of the primary nitro compounds. On the other hand, 4,5-decamethylene-3-phenylsulfonyl-2-isoxazoline N-oxide was obtained from a similar reaction of (phenylsulfonyl)nitromethane with cyclododecene. The formation of the isoxazoline N-oxide can be explained on the basis of the intermediacy of 3,4-bis(phenylsulfonyl)furazan 2-oxide.