Petasis reagent

Other names: bis(η⁵-cyclopentadienyl)dimethyltitanium, dimethyltitanocene

C₁₂H₁₆Ti

19/50 common

The Petasis reagent is a titanocene-based methylenation agent developed by Nicos Petasis in the 1990s as a more stable alternative to Tebbe's reagent. This bright orange-yellow crystalline solid features a titanium center coordinated to two cyclopentadienyl rings and two methyl groups, creating a reactive species that effectively converts carbonyl compounds to terminal alkenes. Unlike Tebbe's reagent, the Petasis reagent does not contain aluminum and can be prepared in advance, stored under inert conditions, and used when needed without complicated handling procedures. It maintains excellent functional group tolerance while exhibiting enhanced thermal stability, making it particularly valuable for complex natural product synthesis where selective late-stage carbonyl olefination is required. The reagent operates through a titanium-methylene (Ti=CH₂) intermediate that forms upon gentle heating, providing a convenient and reliable method for methylenation reactions in modern organic synthesis.