Kornblum–DeLaMare rearrangement

Source: Wikipedia, the free encyclopedia.

The Kornblum–DeLaMare rearrangement is a

prostaglandins.[1]

Kornblum–DeLaMare rearrangement overview

The base can be a hydroxide such as potassium hydroxide or an amine such as triethylamine.

Reaction mechanism

In the reaction mechanism for this organic reaction the base abstracts the acidic α-proton of the peroxide 1 to form the carbanion 4 as a reactive intermediate which rearranges to the ketone 2 with expulsion of the hydroxyl anion 3'. This intermediate gains a proton forming the alcohol 3.

Kornblum-DeLaMare rearrangement Mechanism

Deprotonation and rearrangement can also be a concerted reaction without formation of 4.

An alternative reaction mechanism involving direct

nucleophilic displacement on the peroxide link of the amine followed by an elimination reaction is considered unlikely based on the outcome of this model reaction:[2]

Kornblum-DeLaMare rearrangement alternative mechanism

The peroxide 1 converts to the hydroxyketone 2 by action of

methyl trifluoromethanesulfonate
) fails.

The reaction, formally a rearrangement, ranks under the elimination reactions as already observed by the original authors. Not only alkoxides but any leaving group capable of carrying a negative charge will do for instance nitrate esters R–C(R)(H)–O–NO2.

Related reactions

The corresponding reaction involving an ether is the 1,2-Wittig rearrangement. The reaction course in this rearrangement is different because ether cleavage with carbanion formation is unfavorable. The Pummerer rearrangement in one of its reaction step contains a sulfur variation.

Scope

The original 1951 publication concerned the conversion of potassium t-butyl peroxide and 1-phenylethyl bromide to ultimately

t-butanol with piperidine
as the base:

Kornblum-DeLaMare rearrangement original reaction

The Kornblum–DeLaMare rearrangement can be carried out as an

asymmetric reaction with a suitable chiral amine such as sparteine or a cinchona alkaloid:[3]

Asymmetric reaction

The first step in this

one-pot reaction is 1,4-dioxygenation of 1,3-cycloheptadiene with singlet oxygen and a TPP
catalyst.

References