THE REACTION OF SULFENES WITH DIARYL NITRONES AND N-PHENYLHYDROXYLAMINES

JOHN WILLIAM FIELDHOUSE, Purdue University

Abstract

It has been shown that the interaction of aklanesulfonyl chlorides with tertiary amines generates a reactive intermediate called sulfene (R(,2)C=SO(,2)), which can be trapped with various N, alpha-diaryl nitrones to give an unstable intermediate, 4,5-diaryl-1,2,5-oxathiazole 2,2-dioxide I, which rearranged to 3,4-dihydro-4-aryl-1-oxa-2-thia-5-benz(f) azepine 2,2-dioxide II. Rearrangement of I to II was precluded by the use of N-methyl-alpha-phenyl nitrone or N-(2,6-dimethylphenyl)-alpha-phenyl nitrone; isolation of I was not realized, and only 2-phenyltaurine (III), formaldehyde, and N-methylbenzamide were isolated. An alternate synthesis of I produced only II. II can be acetylated on nitrogen, alkylated on carbon and nitrogen, brominated on the disubstituted aromatic ring and on the aliphatic carbon, oxidized to an N-oxide, protonated on nitrogen, and reductively cleaved to 2-phenylethanethiol and 2-aminophenol. By the use of O('18) nitrone and reductive cleavage of the O('18) azasultone obtained, the 2-aminophenol contained 80-82% of the excess O('18) incorporated in the nitrone. A 4-membered transition state was suggested for the rearrangement of I to II. Reaction of substituted N-phenylhydroxylamines with alkyl or aryl sulfonyl chlorides and triethylamine gave primarily substituted 2-amino-phenols, presumably via N-sulfonyloxyanilines. Reaction of N-phenylhydroxylamine-O('18) and two equivalents of methanesulfonyl chloride and triethylamine, gave N,O-dimethanesulfonyl-2-aminophenol which was isolated and subsequently saponified to N-methanesulfonyl-2-aminophenol which contained none of the excess O('18) incorporated in N-phenylhydroxylamine-O('18). A six membered transition state was postulated for rearrangement of III to IV. The change in the mechanism can be explained on the basis that the sulfonyl oxygens of I are rigidly held via a cyclic five membered ring, thus precluding attack on the benzene ring unless the N-O bond is stretched or broken. Intermediate III is capable of rotating about the N - O - SO(,2) bond and thus forms a six membered ring transition state in which a sulfonyl oxygen becomes attached to the benzene ring.

Degree

Ph.D.

Subject Area

Organic chemistry

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