82817-93-4Relevant academic research and scientific papers
Generation of reactive low-valent titanium species using metal-arenes as efficient organic reductants for TiCl3: Applications to organic synthesis
Rele,Talukdar,Banerji,Chattopadhyay
, p. 2990 - 2994 (2001)
A comprehensive study on the use of metal-arene systems as organic reductants for TiCl3 has resulted in an efficient method for the generation of highly reactive low-valent titanium (LVT) reagents. The activated titanium species could be prepared by refluxing a mixture of substoichiometric amounts of arenes, TiCl3, and Li/Mg in THF or DME. Among the LVT reagents screened, TiCl3 - Li-naphthalene - THF (reagent I) was the best for coupling of carbonyls to olefins. The reagent could carry out the McMurry olefination of both aromatic and aliphatic substrates at a lower temperature and in a much reduced time as compared to the conventional procedures. Subtle changes in the method of preparation of the LVT reagents influenced the stereoisomeric ratio of the olefins. The reagent was also useful for the synthesis of O- and N- heterocycles and vicinal diamines via intramolecular carbonyl coupling and reductive duplication of imines, respectively.
Salt/ligand-activated low-valent titanium formulations: the 'salt effect' on diastereoselective carbon-carbon bond forming SET reactions
Rele, Shyam M.,Nayak, Sandip K.,Chattopadhyay, Subrata
, p. 7225 - 7233 (2008/12/20)
A comprehensive study on the influence of exogenously added electropositive metal salts as promoters/secondary activators on preformed LVT species has resulted in the construction of highly efficient low-valent titanium (LVT) reagents. These salt-activated LVT reagents while exhibiting enhanced chemoselectivity and diastereoselectivity accelerated the reductive olefination rates of aromatic and aliphatic carbonyls under ambient temperature conditions and in much reduced reaction times. The versatility of the salted reagent was further explored in other single electron transfer reactions, namely, imino-pinacol couplings and one-pot synthesis of phenanthrenes from o-alkoxy aromatic carbonyls. We envisage that, in contrast to multiphase heterogeneous colloidal slurries, salt-activated LVT reagents afforded uniformly viscous homogeneous slurries generating a highly reactive monomeric intermetallic LVT complex. Continued judicious exploration of the emerging paradigms by studying the influence of external ligands/auxiliaries/redox agents on LVT reagents, and organometallics in general, will be critical to widen the scope and utility of the classical McMurry reaction and other SET reactions.
