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The pinacol–pinacolone rearrangement is a method for converting a 1,2-diol to a carbonyl compound in organic chemistry. The 1,2-rearrangement takes place under acidic conditions. The name of the rearrangement reaction comes from the rearrangement of pinacol to pinacolone .
Most famously, at least in the classroom, pinacolone arises by the pinacol rearrangement, which occurs by protonation of pinacol (2,3-dimethylbutane-2,3-diol). [4] Industrially pinacolone is made by the hydrolysis of 4,4,5-trimethyl-1,3-dioxane, which is the product of isoprene and formaldehyde via the Prins reaction.
Pinacol is a branched alcohol which finds use in organic syntheses. It is a diol that has hydroxyl groups on vicinal carbon atoms. A white solid that melts just above room temperature, pinacol is notable for undergoing the pinacol rearrangement in the presence of acid and for being the namesake of the pinacol coupling reaction .
The pinacol coupling can be followed up by a pinacol rearrangement. A related reaction is the McMurry reaction, which uses titanium(III) chloride or titanium(IV) chloride in conjunction with a reducing agent for the formation of the metal-diol complex, and which takes place with an additional deoxygenation reaction step in order to provide an ...
He also discovered what is now known as the pinacol rearrangement, whereby 1,2-diols rearrange to aldehydes or ketones under acid catalysis. [ 4 ] [ 5 ] His work involved the preparation of 2,3-dimethyl-2,3-butanediol ( pinacol ) from acetone , [ 6 ] followed by the rearrangement to 3,3-dimethylbutanone ( pinacolone ), which was then oxidised ...
Migratory aptitudes vary in different reactions, depending on multiple factors. [2] In the Baeyer-Villiger reaction, the more substituted group, in general, migrates. [3] In the pinacol rearrangement, the order of migratory aptitude has not been determined unambiguously, [2] but some trends have been determined.
The cationic rearrangement contraction proceeds through the loss of a leaving group and the migration of an endocyclic bond to the carbocation. Pinacol type rearrangements are often used for this type of contraction. [20] Like the expansion reaction this proceeds with an electron donating group aiding in the migration.
Spiro compounds are often prepared by diverse rearrangement reactions. For example, the pinacol-pinacolone rearrangement is illustrated below. [3]: 985 is employed in the preparation of aspiro[4.5]decane. [12]]. The synthesis of a spiro-keto compound form a symmetrical diol