Ring-Closing Metathesis of Titanium–Carbene Complexes Prepared from Thioacetals Having a Carbon–Carbon Double Bond
摘要:
The ring-closing metathesis proceeded to give cycloalkenes in good yields when diphenyl thioacetals having a carbon-carbon double bond were treated with the low-valent titanium species Cp2Ti[P(OEt)(3)](2) in THF at room temperature and then at reflux. This methodology is successfully applied to the preparation of cyclic ethers and sulfides. (C) 2000 Published by Elsevier Science Ltd.
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 Cp2Ti[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. (C) 2000 Elsevier Science Ltd All rights reserved.