Acetoxime O-(2,4,6-trimethylphenyl)sulfonate

[81549-07-7]  · C12H17NO3S  · Acetoxime O-(2,4,6-trimethylphenyl)sulfonate  · (MW 255.20)

(electrophilic aminating reagent for Grignard reagents1)

Physical Data: mp 95-96.5 °C; d 1.12 g cm-3.

Solubility: sol ether, THF; slightly sol benzene; insol hexane.

Preparative Method: Acetone reacts with Hydroxylamine hydrochloride in methanol-aq. NaOH solution to yield acetoxime,2 which is also commercially available. Acetoxime reacts with 2,4,6-trimethylbenzenesulfonyl chloride in triethylamine-DMF to yield acetoxime O-(2,4,6-trimethylphenylsulfonyl)sulfonate.3

Electrophilic Amination.

The addition of organometallic reagents to oximes4 has found limited applicability due to the low electrophilicity of oximes and the a-deprotonation requiring the use of a considerable excess of organometallic reagent (eq 1). There are various scattered reports of reactions of Grignard reagents and organolithiums with oximes that furnish amines, amino acids, aziridines, b-amino alcohols, and other products.5 Ketoximes and their O-substituted derivatives can also serve as electrophilic aminating reagents for Grignard reagents and organolithiums (eq 2).5 So far, acetoxime,6,7 butanone oxime,6 cyclohexanone oxime,8 benzaldoxime,9 isobutyrophenone oxime,10 tetraphenylcyclopentadienone oxime O-tosylate,11 and acetoxime O-(2,4,6-trimethylphenyl)sulfonate1 have been used for amination of Grignard reagents and organolithiums.

Acetoxime O-(2,4,6-trimethylphenyl)sulfonate aminates aryl and cyclohexyl Grignard reagents in moderate to good yields (eq 3).1 The use of Copper(I) Iodide or MgCl2 as a catalyst in the amination of aryl Grignard reagents decreases the reaction time remarkably and/or increases the yield. On addition of 10 mol % of CuI or 20 mol % of MgCl2 in the amination of phenylmagnesium bromide, the yield of aniline is 59% after heating at 75 °C for 22 h compared to 58% in an uncatalyzed reaction of 40 h at the same temperature. On the addition of 7 mol % of MgCl2 in the amination of p-tolylmagnesium bromide, the yield of p-toluidine is 56% after heating at 75 °C for 23 h compared to 36% in an uncatalyzed reaction of 43 h at the same temperature. The use of phenyllithium, phenylzinc chloride, and bromomagnesium diphenylcuprate results in 6%, 0%, and 22% yields respectively.

When comparisons are made between the electrophilic aminating abilities of oximes reported so far, acetoxime O-(2,4,6-trimethylphenyl)sulfonate is seen to be more effective than acetoxime, but less effective than Tetraphenylcyclopentadienone Oxime O-Tosylate. However, the molar ratio of Grignard reagent to oxime that is needed has been reported to be 7:1 in in the amination with tetraphenylcyclopentadienone oxime O-tosylate compared to 1.5:1 in the amination with acetoxime O-(2,4,6-trimethylphenyl)sulfonate. The yield of aniline obtained by aminating phenylmagnesium bromide with acetoxime,6,7 butanone oxime,6 cyclohexanone oxime,8 isobutyrophenone oxime,10 and tetramethylphenylcyclopentadienone oxime O-tosylate11 is 62%, 12%, 25%, 17%, and 95%, respectively.

1. Erdik, E.; Ay, M. Synth. React. Inorg. Met.-org. Chem. 1989, 19, 663.
2. (a) Semon, W. L. JACS 1923, 45, 188; (b) Semon, W. L. OSC 1923, III, 61.
3. Carpino, L. A. JACS 1960, 82, 3133.
4. The Chemistry of the Carbon-Nitrogen Double Bond; Patai, S., Ed.; Wiley: New York, 1970.
5. Erdik, E.; Ay, M. CRV 1989, 89, 1947.
6. Alvernhe, G.; Laurent, A. JCR(S) 1978, 28.
7. Alvernhe, G.; Laurent, A. TL 1972, 1007.
8. Chaabouni, R.; Laurent, A. BSF 1973, 2680.
9. Busch, M; Hobein, R. CB 1907, 40, 2096.
10. Kissman, H. M.; Tarbell, D. S.; Williams, J. JACS 1953, 75, 2959.
11. Hagopian, R. A.; Therien, M. J.; Murdoch, J. R. JACS 1984, 106, 5753.

Ender Erdik

Ankara University, Turkey

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