Use of titanium-based reagents

Tebbe reagent, Grubbs reagent, Petasis reagent, Takeda reagent and Takai reagent are 

McMurry developed a reduction procedure that is used for alkenation of carbonyl compounds in the presence of low-valent titanium (LVT) reagent. The reagent (thought to be a mixture of Ti(0) and Ti(II) species) is formed by the reduction of TiCU or TiCb with a suitable reducing agent (Zn-Cu alloy, LiAlH4 or alkali metal are the most commonly used). 

The dimerization of carbonyl compounds gives symmetrical alkenes . For example, 2-adamantanone (4.76) and retinal (4.78) on reaction with LiAlH4-TiCl3 were converted into adamantylideneadamantane (4.77) and (3-carotene (4.79), respectively. 

The dimerization of aromatic aldehydes is used for the synthesis of substituted stilbenes. The intermolecular unsymmetrical McMurry reaction is not very important in organic syntheses because of the formation of a mixture of products. However, the reaction of two aryl ketones 4.80 and 4.81 functionalized by a sulfonyl and a hydroxyl group, respectively, 

The Z-isomer arises from a consecutive induction of active metallic titanium surface to the polydented pinacolic intermediate formed by homolytic coupling of a radical anion species generated from reduction of two carbonyl compounds that is followed by subsequent demetallation and deoxygenation reactions. In this regard, the phenoxy-Ti-sulfone induction plays the key role for Z-stereoselection by forcing the phenoxy and sulfone moieties to be positioned on the same side. 

---