Synthesis of Sulfur-Containing Polyfunctional Terpenoids from (-)-Carvone

Reactions of (-)-carvone with aliphatic, aromatic, heterocyclic, and functional thiols, catalyzed with potassium carbonate, gave the corresponding derivatives in high yields. Isopropyl mercaptan, 2-mercaptoethanol, furfuryl mercaptan, and N-acetylcysteine add across the endocyclic double bond of (-)-carvone with the predominant formation of the isomers with the S configuration of C³, whereas addition of hexadecyl mercaptan and 1,2-ethanedithiol mainly yields the R isomers.     

Reactions of Single-electron Oxidation and Reduction of Sulfides of the Azulene Series

Single-electron oxidation in acetonitrile and reduction in DMF of sulfides of 3-RS-1,4-dimethyl-7- ethylazulenes (R = Me, Et, Ph, p-MeC₆H₄, p-MeOC₆H₄, N-1-phenyltetrazolyl) leads to stable radical cations and radical anions, respectively. The found reduction potentials of sulfides of the azulene series are close to those of natural and synthetic bioantioxidants. In the radical cations the unpaired electron is essentially delocalized over the cyclopentadienyl fragment of the molecule, and the sulfide group in large measure defines the distribution of spin density. In the radical anion spin density is delocalized in the tropylium cycle, and the influence of the sulfide group is insignificant. Electrochemical oxidation of unsubstituted 1,4-dimethyl-7-ethylazulene results in the formation of a dimeric radical cation.