Titanium Metallacycles as Intermediates in the Synthesis of Acyclic and Heterocyclic Compounds

Abstract

Sequential reactions of the titanocene methylidene complex, [Cp₂Ti=CH₂], with various unsaturated organic substrates lead to the facile preparation of a number of acyclic and heterocyclic compounds, including pyridine and pyrimidine derivatives, conjugated dienes, and ß-ketoenamines. These reactions are discussed within the context of pericyclic organometallic reactivity, with particular focus on [4 + 2] cycloaddition reactions of 1-metalla-1,3-dienes. 1. Introduction 2. Reactivity of Titana-2-cyclobutenes with Nitriles 3. Reactivity of Titana-2-cyclobutenes with Ketones and Aldehydes 4. 1-Aza-2-titana-1(4)-cyclobutenes as Reactive Intermediates 5. Applications to Main-Group Heterocyclic Chemistry