Importance of Structure of α,β-Ethylenic Ketones during Their Reductive Coupling Promoted by the TiCl4-Mg Reagent

Article abstract of DOI:10.1021/jo00265a030

In most cases, the reductive coupling of α,β-ethylenic ketones by the TiCl4-Mg reagent leads to 1,3,5-trienes and bisallylic pinacols.Some α,β-enones of s-cis configuration, such as (+)-pulegone, show a particular reactivity: formation of dihydro ketones in the presence of tert-butyl alcohol and reductive alkylation with allylic halides or benzyl bromide.Results are accordance with a polymeric structure for the native low-valent titanium species, and in the case of some s-cis-enones, they can be explained by the intervention of a oxametallacyclopentene.