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# Baylis Hillman Reaction

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 Sub Topics Functionalized allyl alcohols are important synthetic intermediates in multi step organic transformations and new methods for their preparation have always attached the attention of organic chemists. The Bayllis-Hillman reaction provides ready access to such alcohols. This reaction of vinylic esters ketones and nitriles with aldehydes in the presence of catalytic amounts of a trialkylamine, for example, DABCO $\alpha$-metthylene-$beta$-hydroxy moieties.However the BH reaction has several drawbacks such as slow reaction rate and lack of reactivity with ketones. The lack of reactivity with $\beta$-substituted vinyilic substrates also limits the scope of this reaction. Due to the polymerization of fluorocarbonyls in the presence of amines, BH reactions of perfluoroaldees and ketones are difficult.

## Mechanism

The commonly accepted mechanism for the Baylis-Himann reaction which was subsequently refined by others. The reaction involves first a reversible Micheal addition of the nucleophilic catalyst onto the activated alkene to produce an enolate followed by an aldolic reaction to aldehyde or imine to result in zwitterionic intermediate. An intramolecuar proton transfer to form intermediate and an E1 and E2 elimination to generate the product while the catalyst is released to complete the cycle. This mechanism was based on pressure dependence, rate and kinetic isotope effect. The aldolic reaction is the rate determining step.