Enolizable aldehydes can undergo Cannizzaro reactions under specific conditions
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Standard organic chemistry references state that classical Cannizzaro reactions occur with non-enolizable aldehydes lacking alpha-hydrogens, whereas specialized or enzyme-catalyzed approaches demonstrate that enolizable aldehydes can undergo disproportionation under specific conditions.
The biocatalytic asymmetric disproportionation of aldehydes catalyzed by horse liver alcohol dehydrogenase (HLADH) was assessed in detail on a series of racemic 2-arylpropanals. Statistical optimization by means of design of experiments (DoE) allowed the identification of critical interdependencies between several reaction parameters and revealed a specific experimental window for reaching an 'optimal compromise' in the reaction outcome. The biocatalytic system could be applied to a variety of 2-arylpropanals and granted access in a redox-neutral manner to enantioenriched (<i>S</i>)-profens and profenols following a parallel interconnected dynamic asymmetric transformation (PIDAT). The reaction can be performed in aqueous buffer at ambient conditions, does not rely on a sacrificial co-substrate, and requires only catalytic amounts of cofactor and a single enzyme. The high atom-efficiency was exemplified by the conversion of 75 mM of <i>rac</i>-2-phenylpropanal with 0.03 mol% of HLADH in the presence of ∼0.013 eq. of oxidized nicotinamide adenine dinucleotide (NAD<sup>+</sup>), yielding 28.1 mM of (<i>S</i>)-2-phenylpropanol in 96% <i>ee</i> and 26.5 mM of (<i>S</i>)-2-phenylpropionic acid in 89% <i>ee</i>, in 73% overall conversion. Isolated yield of 62% was obtained on 100 mg-scale, with intact enantiopurities.
disproportionation of two molecules of a non-enolizable aldehyde to give a primary alcohol and a carboxylic acid. Cannizzaro first accomplished this transformation
The Cannizzaro reaction, named after its discoverer Stanislao Cannizzaro, is a chemical reaction which involves the base-induced disproportionation of two molecules of a non-enolizable aldehyde to give a primary alcohol and a carboxylic acid.
Cannizzaro first accomplished this transformation in 1853, when he obtained benzyl alcohol and potassium benzoate from the treatment of benzaldehyde with po
The Cannizzaro reaction, named after its discoverer Stanislao Cannizzaro, is a chemical reaction which involves the base-induced disproportionation of two molecules of a non-enolizable aldehyde to give a primary alcohol and a carboxylic acid.
Certain ketones can undergo a Cannizzaro-type reaction, transferring one of their two carbon groups rather than the hydride that would be present on an aldehyde.
A nitrogen variant was discovered in 2024. In this aza-Cannizzaro reaction, the aldehyde portions of two glyoxylic acid molecules react in an ammonium-rich aqueous solution at neutral pH react and disproportionate to form an amine and an amide. The key hydride-transfer step is thought to occur from the hemiaminal derived from one aldehyde to the iminium derived from the other aldehyde. This specific example is possibly relevant to prebiotic chemistry and chemical ecosystems because the precursors are though to have existed well before life began and the reaction provides a viable prebiotic pathway for nitrogen incorporation and the synthesis of glycine, a common α-amino acid.
The core autocatalytic cycle of the formose reaction may be enhanced or eroded by the presence of simple molecules at life's origin. Utilizing quantum chemistry, we calculate the thermodynamics and kinetics of reactions both within the core cycle and those that deplete the reactants and intermediates, such as the Cannizzaro reaction. We find that via disproportionation of aldehydes into carboxylic acids and alcohols, the Cannizzaro reaction furnishes simple catalysts for a variety of reactions. We also find that ammonia can catalyze both in-cycle and Cannizzaro reactions while hydrogen sulfide does not; both, however, play a role in sequestering reactants and intermediates in the web of potential reactions.
The Cannizzaro reaction has emerged as a versatile synthetic tool for the construction of functionalized molecules. Dating back to the 19th century, this reaction, though initially used for the synthesis of an alcohol and acid functionality from aldehydes, has henceforth proven useful to generate diverse molecular entities using both intermolecular and intramolecular synthetic strategies. Immense applications in the synthesis of hydroxy acids and esters, heterocycles, fused carbocycles, natural products, and others with broad substrate scope have raised profound interest from methodological and synthetic standpoints. The ongoing development of reagents, solvents, and technologies for the Cannizzaro reaction reflects the broader trend in organic synthesis towards more sustainable and efficient practices. The focus of this review is to highlight some recent advances in synthetic strategies and applications of the Cannizzaro reaction towards the synthesis of potentially useful molecules.
starting from methanol. Oxidation of aldehydes with air using cobalt and manganese catalysts. The required aldehydes can be obtained from alkenes by hydroformylation
In organic chemistry, a carboxylic acid is a polar, organic acid that contains a carboxyl group (−C(=O)−OH) attached to an R-group. The general formula of a carboxylic acid is often written as R−COOH or R−CO2H, sometimes as R−C(O)OH, with R referring to an organyl group (e.g., alkyl, alkenyl, aryl), or hydrogen, or other groups. Carboxylic acids occur widely. Important examples include the amino a
Carbonylation of alcohols as…
Oxidation of primary alcohols or aldehydes with strong oxidants such as potassium dichromate, Jones reagent, potassium permanganate, or sodium chlorite. The method is more suitable for laboratory conditions than the industrial use of air, which is "greener" because it yields less inorganic side products such as chromium or manganese oxides.
Oxidative cleavage of olefins by ozonolysis, potassium permanganate, or potassium dichromate.
Hydrolysis of nitriles, esters, or amides, usually with acid- or base-catalysis.
Carbonation of a Grignard reagent and organolithium reagents:
RLi + CO2 → RCO−2Li+
RCO−2Li+ + HCl → RCO2H + LiCl
Halogenation followed by hydrolysis of methyl ketones in the haloform reaction
Base-catalyzed cleavage of non-enolizable ketones, especially aryl ketones:
R−C(=O)−Ar + H2O → R−CO2H + ArH
Disproportionation of an aldehyde in the Cannizzaro reaction
Rearrangement of diketones in the benzilic acid rearrangement
Involving the generation of benzoic acids are the von Richter reaction from nitrobenzenes and the Kolbe–Schmitt reaction from phenols.
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