Onion essential oil chemistry. cis- and trans-2-mercapto-3,4-dimethyl-2,3-dihydrothiophene from pyrolysis of bis(1-propenyl) disulfide

Article abstract of DOI:10.1016/S0040-4039(00)97788-8

Heating the onion oil component bis (1-propenyl) disulfide gives cis- and trans-2-mercapto-3,4-dimethyl-2,3-dihydrothiophene which can lose H₂S upon further heating giving 3,4-dimethylthiophene. A dithio-Claisen rearrangement is proposed for the key step.