Lukas, who occasionally comments on this blog, sent me the following challenge. In a recent article[1] he had proposed that the stereochemical outcome (Z) of reaction between a butenal and thioacetic acid as shown below arose by an unusual concerted cycloaddtion involving an S-H bond. He wrote in the article “…this scheme … recommends itself for evaluation by in silico methods“. I asked if the answer could be posted here, and he agreed. So here it is.
References
- L. Hintermann, and A. Turočkin, "Reversible Generation of Metastable Enols in the 1,4-Addition of Thioacetic Acid to α,β-Unsaturated Carbonyl Compounds", The Journal of Organic Chemistry, vol. 77, pp. 11345-11348, 2012. https://doi.org/10.1021/jo3021709