Everything about Kornblum Delamare Rearrangement totally explained
The
Kornblum–DeLaMare rearrangement is a
rearrangement reaction in
organic chemistry in which a primary or secondary
organic peroxide is converted to the corresponding
ketone and
alcohol under
base catalysis. The reaction is relevant as a tool in
organic synthesis and is a key step in the
biosynthesis of
prostaglandins.
»
The base can be an
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.
»
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:
»
The peroxide
1 converts to the hydroxyketone
2 by action of
triethylamine but the alternative route through
hydroxylamine 3 by nucleophilic displacement with
Lithium diisopropylamide and the
ammonium salt 4 (by
methylation with
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-NO
2.
Related reactions
The corresponding reaction involving an
ether is the
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
benzophenone and
t-butanol with
piperidine as the base:
The Kornblum-DeLaMare rearrangement can be carried out as an
asymmetric reaction with a suitable
chiral amine such as
sparteine or an
AD-mix variation:
»
The first step in this
one-pot reaction is 1,4-dioxygenation of 1,3-cycloheptadiene with
singlet oxygen and a
TPP catalyst.
Further Information
Get more info on 'Kornblum Delamare Rearrangement'.
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