Boron Trisulfide

B2S3

[12007-33-9]  · B2S3  · Boron Trisulfide  · (MW 117.80)

(sulfuration agent of carbonyl to thiocarbonyl group;1 sulfuration agent of phosphine oxide to phosphine sulfide;8 dehydrogenating agent;11 synthetic reagent for boroles14)

Physical Data: monoclinic colorless crystals; mp 563 °C (dec); d 1.55 g cm-3.

Solubility: sol ethanol, but decomposes.

Form Supplied in: white solid.

Handling, Storage, and Precautions: the dry solid is very flammable under air and immediately reacts with water to give boric acid and hydrogen sulfide.

Sulfuration Agent of Carbonyl to Thiocarbonyl Functional Group.

Boron trisulfide is used as a sulfuration agent in synthetic chemistry; it is especially efficient for the conversion of carbonyl to thiocarbonyl. 1,3,4,6-Tetrathiapentalene-2,5-dione is sulfurized with boron trisulfide in toluene under reflux to give a mixed carbonyl-thiocarbonyl compound. When a solid mixture of 1,3,4,6-tetrathiapentalene-2,5-dione and boron trisulfide is heated at 100 °C for long time, 1,3,4,6-tetrathia-2,5-dithione is formed as a yellow solid (eq 1).1

Boron trisulfide has advantages over Phosphorus(V) Sulfide for converting non-enolizable ketones such as 2-pyrones and 4-pyrones to the corresponding thiones (eq 2).2 Boron trisulfide is very active and often effective at rt. 4-Selenapyranthione is formed from 4-selenapyranone by treating with boron trisulfide in chloroform (eq 3).3

The reaction of boron trisulfide with aromatic aldehydes and aliphatic aldehydes gives a good yield of the corresponding thioaldehyde trimer via the monomer (eq 4).4

Steliou has reported that the treatment with Bis(tricyclohexyltin) Sulfide-Boron Trichloride converts carbonyls into the thiocarbonyl analogs in high yield. The intermediate formation of boron trisulfide has been postulated. This sulfurating method is efficient even with highly hindered ketones inert to direct sulfuration (eq 5).5 The yields of the thiocarbonyl compounds obtained are shown in Table 1.

Some orthoesters are also conveniently sulfurized with boron trisulfide to give the corresponding thioesters (eq 6).6

When methyl benzoate and boron trisulfide are refluxed under nitrogen for 28 h, the sulfurized cyclization product 2,3,4,5-tetraphenylthiophene is obtained (eq 7).4,7 Boron trisulfide reacts with acyl complexes (C5H5)Fe(CO)2COR to give dithiocarboxylate complexes (C5H5)Fe(CO)2SCSR and (C5H5)Fe(CO)SSCR. Generally, the reactions with boron trisulfide are faster than those with phosphorus pentasulfide (eq 8).8

Sulfuration Agent for Other Compounds.

Boron trisulfide transforms tertiary phosphine oxides into the corresponding phosphine sulfides with net retention of configuration at phosphorus (eq 9).9 Sulfoxides are reduced to give sulfides, presumably through an intermediate sulfothioxide (eq 10).10

Dehydrogenating Agent.

Boron trisulfide behaves as a dehydrogenating agent with organic molecules containing labile hydrogens such as alcohols11 and thiols12 to give the corresponding orthoester and orthothioester. Moreover, several nitrogen bases, e.g. aniline and N,N-dimethylhydrazine, react with boron trisulfide under nitrogen in the dark to form tris(phenylamino)boron and tris(N,N-dimethylhydrazo)boron respectively (eq 11).13 Catechol also reacts with boron trisulfide to give 2,2-o-phenylenedioxybis(1,3,2-benzodioxaborole), while only the hydroxy function of salicylic acid reacts to give a quantitative yield of tris(o-carboxylphenoxy)borane. Phthalic acid, succinic acid, and maleic acid are not sulfinated by boron trisulfide (eq 12).14

Related Reagents.

2,4-Bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-Disulfide; Bis(tricyclohexyltin) Sulfide-Boron Trichloride; Bis(trimethylsilyl) Sulfide.


1. Schumaker, R. R.; Engler, E. M. JACS 1977, 99, 5521.
2. Dean, F. M.; Goodchild, J.; Hill, A. W. JCS(C) 1969, 2192.
3. Es-Seddiki, S.; Le Coustumer, G.; Mollier, Y. TL 1981, 22, 2771.
4. Jerumanis, S.; Lalancette, J. M. CJC 1964, 42, 1928.
5. Steliou, K.; Mrani, M. JACS 1982, 104, 3104.
6. Lalancette, J. M.; Beauregard, Y. TL 1967, 5169.
7. Yager, B. J.; Wootan, Jr. W. L. CJC 1978, 56, 1043.
8. Busetto, L.; Palazzi, A. JOM 1977, 129, C55.
9. Maryanoff, B. E.; Tang, R.; Mislow, K. CC 1973, 273.
10. Baechler, R. D.; Daley S. K. TL 1978, 101.
11. Lalancette, J. M. CJC 1964, 42, 2356.
12. Brault, J.; Lalancette, J. M. CJC 1964, 42, 2903.
13. Jerumanis, S.; Lalancette, J. M. JOC 1966, 31, 1531.
14. Jerumanis, S.; Begin, P. A.; Cong, D. V. CJC 1972, 50, 1675.

Ryu Sato

Iwate University, Morioka, Japan



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