[108-98-5]  · C6H6S  · Thiophenol-Azobisisobutyronitrile  · (MW 110.19) (AIBN)

[78-67-1]  · C8H12N4  · Thiophenol-Azobisisobutyronitrile  · (MW 136.22)

(preparation of benzenethiyl radicals with subsequent use in radical addition reactions of thiophenol to alkenes and alkynes;1-4 alkene isomerizations5)

Preparative Methods: prepared from Thiophenol and Azobisisobutyronitrile, both of which are commercially available.

Synthesis of Sulfide Derivatives from Alkenes.

Thermally induced decomposition of AIBN to cyanopropyl radicals initiates hydrogen abstraction from thiophenol in the title reagent system to give benzenethiyl radicals. Kinetic studies involving the addition of the thiol radical to 1,4-divinylbenzene (eq 1), using a catalytic amount of AIBN, demonstrate that the sulfide-containing styrene monomer can be prepared in high yield by carrying out the reaction at 60 °C with an equimolar ratio of thiophenol and the alkene.1 More vigorous reaction conditions (170 °C) are necessary, however, in the thio radical addition to triethoxyvinylsilane (eq 2), since no reaction takes place even on prolonged heating at 100-110 °C.2

Synthesis of Vinyl Sulfides from Alkynes.

The AIBN radical-initiated addition reaction of thiophenol to the terminal alkyne of a ynoic acid (eq 3) derivative provides the corresponding vinyl sulfide intermediate used in the synthesis of cyclohexanone derivatives.3 This process has also been used in the synthesis of a chiral diene (eq 4) from an enyne precursor, a key intermediate in the enantiospecific total synthesis of (+)-compactin.4

Thiophenol-Mediated Alkene Inversion.

trans-Substituted alkenes containing a quarternary carbon center adjacent to the double bond are difficult to prepare by standard techniques, such as the Wittig reaction or by chemical reduction of the corresponding alkyne. However, they have been prepared by isomerizing the readily available cis-alkene using thiophenol-AIBN (eq 5).5

Heterocyclic Synthesis.

The reaction of 1,2,3-benzothiadiazole with PhSH/AIBN in refluxing EtOAc provides a mixture of products including dibenzo[c,e]-o-dithiin (1), thianthrene (2), and 2-(phenylthio)diphenyl disulfide (3).6

1. Jiang, J.; Kobayashi, E.; Obata, T.; Furukawa, J. Polym. J. (Tokyo) 1990, 22, 963.
2. Seshadri, T.; Haupt, H. J. Anal. Chem. 1988, 60, 47.
3. Crich, K.; Eustace, K. A.; Fortt, S. M.; Ritchie, T. J. T 1990, 46, 2135.
4. Grieco, P. A.; Lis, R.; Zelle, R. E.; Finn, J. JACS 1986, 108, 5908.
5. Schwarz, M.; Graminski, G. F.; Waters, R. M. JOC 1986, 51, 260.
6. Benati, L.; Montevecchi, P. C.; Tundo, A.; Zanardi, G. JOC 1976, 41, 1331.

Patrick M. O'Brien

Parke-Davis Pharmaceutical Research, Ann Arbor, MI, USA

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