Synthesis of carbocycles and heterocycles by the titanocene(II)-promoted reactions of thioacetals

Abstract

The preparation of carbocyclic and heterocyclic compounds by the low-valent titanium species-promoted intramolecular reactions of thioacetals was studied. The cyclization of thioacetals having an olefin moiety proceeded with the loss of terminal olefin carbon to produce the corresponding five-, six-, and seven-membered cycloalkenes when they were treated with the low-valent titanium species Cp 2Ti[P(OEt) 3] 2. This method has been successfully applied to the syntheses of cyclic unsaturated amines and ethers. When S-[3,3-bis(phenylthio)propyl] thioalkanoates were treated with the low-valent titanium species, the intramolecular carbonyl olefination proceeded to produce 5-substituted 2,3-dihydrothiophenes.