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[1] If the diazene intermediate is able to undergo a sigmatropic rearrangement, this process occurs in preference to the simple radical reduction to give a hydrocarbon with a transposed π bond. For example, in the Myers allene synthesis, one of the two π bonds of the alkyne of a propargyl alcohol shifts, forming an allene. [1]
The reaction mechanism of the Mitsunobu reaction is fairly complex. The identity of intermediates and the roles they play has been the subject of debate. Initially, the triphenyl phosphine (2) makes a nucleophilic attack upon diethyl azodicarboxylate (1) producing a betaine intermediate 3, which deprotonates the carboxylic acid (4) to form the ion pair 5.
[1] Favorskii reaction and the possible subsequent rearrangement. When the carbonyl is an aldehyde (R"=H), a rearrangement can occur to generate enone, although the secondary propargylic alcohol can be isolated in some cases. [2] When this rearrangement is catalyzed by an acid, it is called Meyer–Schuster rearrangement.
In organic chemistry, carbonyl reduction is the conversion of any carbonyl group, usually to an alcohol. It is a common transformation that is practiced in many ways. [1] Ketones, aldehydes, carboxylic acids, esters, amides, and acid halides - some of the most pervasive functional groups, -comprise carbonyl compounds.
The Wharton olefin synthesis or the Wharton reaction is a chemical reaction that involves the reduction of α,β-epoxy ketones using hydrazine to give allylic alcohols. [1] [2] [3] This reaction, introduced in 1961 by P. S. Wharton, is an extension of the Wolff–Kishner reduction.
The reaction mechanism [5] begins with the protonation of the alcohol which leaves in an E1 reaction to form the allene from the alkyne. Attack of a water molecule on the carbocation and deprotonation is followed by tautomerization to give the α,β-unsaturated carbonyl compound. Edens et al. have investigated the reaction mechanism. [6]
The aluminium based Meerwein–Ponndorf–Verley reduction can be performed on prochiral ketones leading to chiral alcohols. The three main ways to achieve the asymmetric reduction is by use of a chiral alcohol hydride source, use of an intramolecular MPV reduction, or use of a chiral ligand on the aluminium alkoxide.
Clemmensen reduction is a chemical reaction described as a reduction of ketones or aldehydes to alkanes using zinc amalgam and concentrated hydrochloric acid (HCl). [1] [2] This reaction is named after Erik Christian Clemmensen, a Danish-American chemist. [3] Scheme 1: Reaction scheme of Clemmensen Reduction.