Continuing an exploration of the mechanism of this reaction, an alternative new mechanism was suggested in 1989 (having been first submitted to the journal ten years earlier!).[1] Here the key intermediate proposed is a thiirenium cation (labelled 8 in the article) and labelled Int3 below.
References
- M. Carmack, "The willgerodtâkindler reactions. 7. The mechanisms", Journal of Heterocyclic Chemistry, vol. 26, pp. 1319-1323, 1989. http://dx.doi.org/10.1002/jhet.5570260518