Tebbe's reagent

Other names: μ-Chloro[di(cyclopenta-2,4-dien-1-yl)]dimethyl(μ-methylene)titanium­aluminum

C₁₃H₁₈AlClTi

17/50 common

Tebbe's reagent is a distinctive organometallic complex containing both titanium and aluminum that serves as a powerful methylenation agent. First developed by Fred Tebbe at DuPont in the 1970s, this reagent converts ketones and esters to their corresponding alkenes and enol ethers, respectively. Unlike the traditional Wittig reaction, Tebbe's reagent can efficiently methylenate sterically hindered carbonyl compounds and is notably less basic, allowing for greater functional group tolerance. Its structure features a titanocene fragment (Ti(Cp)₂) connected to aluminum via a bridging methylene (CH₂) group and chloride. In its pure form, Tebbe's reagent appears as bright red crystals that decompose rapidly in air, necessitating preparation and handling under rigorously inert conditions. This pyrophoric nature makes it somewhat challenging to work with, but its unique reactivity continues to make it valuable in complex molecule synthesis, particularly for late-stage functionalization of sensitive natural products. Modern synthetic chemists often employ the more stable Petasis reagent or Nysted reagent as alternatives, though Tebbe's reagent remains the historical archetype of this important class of olefination reagents.