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In organic chemistry, the ene reaction (also known as the Alder-ene reaction by its discoverer Kurt Alder in 1943) is a chemical reaction between an alkene with an allylic hydrogen (the ene) and a compound containing a multiple bond (the enophile), in order to form a new σ-bond with migration of the ene double bond and 1,5 hydrogen shift.
The ene reaction is one of the most common forms of group transfer reactions, where an allylic hydrogen is transferred to an alkene in a cyclic concerted mechanism. The ene reaction is further divided into subgroups including intramolecular ene, metallo-ene, and carbonyl ene reactions. [ 8 ]
The carbonyl-ene reaction is almost always catalyzed by Lewis acids in synthetic applications. [27] A stepwise or a largely asynchronous mechanism has been proposed for the catalyzed reaction based on kinetic isotope effect studies. [28] Nonetheless, cyclic transition states are frequently invoked to interpret diastereoselectivity.
In organic chemistry, the Conia-ene reaction is an intramolecular cyclization reaction between an enolizable carbonyl such as an ester or ketone and an alkyne or alkene, giving a cyclic product with a new carbon-carbon bond.
The Schenck ene reaction or the Schenk reaction is the reaction of singlet oxygen with alkenes to yield hydroperoxides. The hydroperoxides can be reduced to allylic alcohols or eliminate to form unsaturated carbonyl compounds. It is a type II photooxygenation reaction, and is discovered in 1944 by Günther Otto Schenck. [1]
The term enol is an abbreviation of alkenol, a portmanteau deriving from "-ene"/"alkene" and the "-ol". Many kinds of enols are known. [1] Keto–enol tautomerism refers to a chemical equilibrium between a "keto" form (a carbonyl, named for the common ketone case) and an enol.
Scheme 6. Carbonyl-ene reaction versus Prins reaction. in green: capture of the carbocation by additional carbonyl reactant. In this mode the positive charge is dispersed over oxygen and carbon in the resonance structures 8a and 8b. Ring closure leads through intermediate 9 to the dioxane 10. An example is the conversion of styrene to 4-phenyl ...
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