Antimony(III) Chloride


[10025-91-9]  · Cl3Sb  · Antimony(III) Chloride  · (MW 228.11)

(Lewis acid catalyst for electrophilic aromatic substitution;1,2 halo-3 and stibinodediazoniation4 of diazonium salts; fluorination of sulfoxides5,6 and thioethers7 with DAST)

Alternate Names: antimony trichloride; trichlorostibine.

Physical Data: mp 73 °C; bp 223 °C, 143 °C/70 mmHg; d 3.14 g cm-3.

Solubility: sol H2O (1 g/10.1 mL, at 25 °C); sol acetone, alcohol, benzene, chloroform, 1,2-dichloroethane, dichloromethane; insol pyridine.

Form Supplied in: colorless, hygroscopic crystals which fume in moist air.

Handling, Storage, and Precautions: poisonous; moisture-sensitive, corrosive, and irritant. For best results, anhydrous SbCl3 should be handled in an anhydrous, inert atmosphere (dry box or glove bag in humid laboratories), or manipulated rapidly to minimize contact with air and moisture. Use in a fume hood.

Electrophilic Aromatic Substitution.

Antimony(III) chloride has been used as a Lewis acid catalyst for Friedel-Crafts reactions. Thus treatment of benzene with benzoyl chloride/SbCl3 at 155 °C gives benzophenone in good yield.1a However, this conversion and other Friedel-Crafts reactions catalyzed by SbCl3 are slower, require higher temperatures, and give lower yields than with the more reactive Lewis acids Aluminum Chloride, Iron(III) Chloride, and Antimony(V) Chloride.1 Treatment of benzene with Cl2/NOCl and molten SbCl3 (135-145 °C) gives chlorobenzene.2

Nonaqueous Diazotization/Halodediazoniation, and Stibinodediazoniation.

Treatment of 2-amino-6-substituted purine nucleosides with t-butyl nitrite and catalytic amounts of antimony(III) chloride in a chlorinated hydrocarbon solvent gave 2-chloro-6-substituted derivatives smoothly (eq 1a). The corresponding 2-bromo analogs were obtained when antimony(III) bromide was used in a brominated hydrocarbon solvent (eq 1b).3 In contrast, diazotization of aniline with pentyl nitrite followed by addition of SbCl3 gave a stable benzenediazonium/SbCl3 salt.4a Such antimony salts can also be prepared by aqueous diazotization,4b-e and they have been used for the synthesis of a variety of aryl antimony compounds such as phenylstibonic acids.4

Fluorination of Sulfoxides and Thioethers.

Antimony(III) chloride is a potent catalyst for the conversion of sulfoxides to a-fluoro thioethers with N,N-Diethylaminosulfur Trifluoride (DAST).5 Thioanisole sulfoxide gave fluoromethyl phenyl sulfide in 88% yield (eq 2).5b Zinc Iodide was the catalyst originally reported for this fluoro-Pummerer transformation,6a but SbCl3 is markedly superior.5,6b Since sulfides afford a-fluoro thioethers directly upon treatment with DAST/SbCl3,7 prior oxidation of sulfides to their sulfoxides is not necessary for this transformation. Thus thioanisole gave fluoromethyl phenyl sulfide in 94% yield (eq 2) and the more complex 2,3-di-O-acetyl-5-adenosyl phenyl (and p-anisyl) sulfides gave the 5-fluoro derivatives in ~60% yields (eq 3).7 McCarthy has developed access to terminal vinyl fluorides with derived a-fluoro sulfoxides and sulfones.6

Antimony(III) Chloride/Reducing Metal Systems.

Zero-valent antimony species prepared by reduction of SbCl3 with aluminum or iron effect allylations of aldehydes with allyl halides at 25 °C to give homoallylic alcohols in high yields.8a,b SbCl3/Al or SbCl3/Zn in aqueous DMF (or D2O/DMF) are efficient systems for the reduction of aldehydes to alcohols.8b,c Electroreduction of acetophenone to 1-phenylethanol occurred on a lead cathode in the presence of catalytic SbCl3.9 Quantitative conversions of aldehydes to their methyl or ethyl acetals have been effected with Al (or Fe)/SbCl3(cat.)/MeOH (or EtOH).8b

1. (a) Menshutkin, B. N. J. Russ. Phys. Chem. Soc. 1913, 45, 1710 (CA 1914, 8, 910). (b) Cauguil, G.; Barrera, H. BSF 1951, 84. (c) Russell, G. A. JACS 1959, 81, 4834.
2. Morozovskii, A. I.; Solomonov, A.; Skidaev, V. I.; Gertsen, P. P. Zh. Prikl. Khim. (Leningrad) 1989, 62, 1140 (CA 1989, 111, 117 728v).
3. Robins, M. J.; Uznanski, B. CJC 1981, 59, 2608.
4. (a) Nesmeyanov, A. N.; Gipp, N. K.; Makarova, L. G.; Mozgova, K. K. IZV 1953, 298 (CA 1954, 48, 6391). (b) May, P. JCS 1912, 101, 1037. (c) Gray, W. H. JCS 1926, 128, 3174. (d) Nesmeyanov, A. N.; Kocheshkov, K. A. BAU 1944, 416 (CA 1945, 39, 4320). (e) Doak, G. O.; Steinman, H. G. JACS 1946, 68, 1987.
5. (a) Robins, M. J.; Wnuk, S. F. TL 1988, 29, 5729. (b) Wnuk, S. F.; Robins, M. J. JOC 1990, 55, 4757.
6. (a) McCarthy, J. R.; Peet, N. P.; LeTourneau, M. E.; Inbasekaran, M. JACS 1985, 107, 735. (b) McCarthy, J. R.; Matthews, D. P.; Edwards, M. L.; Stemerick, D. M.; Jarvi, E. T. TL 1990, 31, 5449.
7. Robins, M. J.; Wnuk, S. F. JOC 1993, 58, 3800.
8. (a) Wang, W.-B.; Shi, L.-L.; Xu, R.-H.; Huang, Y.-Z. JCS(P1) 1990, 424. (b) Wang, W.-B.; Shi, L.-L.; Huang, Y.-Z. T 1990, 46, 3315. (c) Wang, W.-B.; Shi, L.-L.; Huang, Y.-Z. TL 1990, 31, 1185.
9. Ikeda, Y.; Manda, E. CL 1989, 839.

Morris J. Robins & Stanislaw F. Wnuk

Brigham Young University, Provo, UT, USA

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