| Nierenstein reaction | |
|---|---|
| Named after | Maximilian Nierenstein |
| Reaction type | Carbon-carbon bond forming reaction |
The Nierenstein reaction is an organic reaction describing the conversion of an acid chloride into a haloketone with diazomethane. [1] [2] It is an insertion reaction in that the methylene group from the diazomethane is inserted into the carbon-chlorine bond of the acid chloride.
The reaction proceeds through a diazonium salt intermediate formed by nucleophilic acyl substitution of the chloride with diazomethyl anion. The chloride then displaces the diazo group in an SN2 reaction, with N2 as the leaving group.
If excess diazomethane is present during the reaction, it can act as a base, abstracting a hydrogen from the diazonium-salt intermediate. The result is a neutral diazoketone, which does not react with the chloride. Instead, the byproduct, diazonium-methyl from the other diazomethane molecule, can be attacked by the chloride to produce chloromethane. The unreactive diazoketone can be re-activated and reacted by treatment with hydrogen chloride to give the normal Nierenstein product.
In some cases, even limiting the amount of diazomethane gives a reaction process that stalls via the neutral diazoketone pathway, requiring the addition of HCl gas to rescue it. [3]
One original 1924 Nierenstein reaction: [4]
and a reaction starting from benzoyl bromide going haywire with formation of the dioxane dimer: [5]
In chemistry, an ester is a chemical compound derived from an acid in which at least one –OH (hydroxyl) group is replaced by an –O–alkyl (alkoxy) group. Usually, esters are derived from substitution reaction of a carboxylic acid and an alcohol. Glycerides, which are fatty acid esters of glycerol, are important esters in biology, being one of the main classes of lipids, and making up the bulk of animal fats and vegetable oils. Esters with low molecular weight are commonly used as fragrances and found in essential oils and pheromones. Phosphoesters form the backbone of DNA molecules. Nitrate esters, such as nitroglycerin, are known for their explosive properties, while polyesters are important plastics, with monomers linked by ester moieties. Esters usually have a sweet smell and are considered high-quality solvents for a broad array of plastics, plasticizers, resins, and lacquers. They are also one of the largest classes of synthetic lubricants on the commercial market.
The Friedel–Crafts reactions are a set of reactions developed by Charles Friedel and James Crafts in 1877 to attach substituents to an aromatic ring. Friedel–Crafts reactions are of two main types: alkylation reactions and acylation reactions. Both proceed by electrophilic aromatic substitution.
In chemistry, an electrophile is a chemical species that forms bonds with nucleophiles by accepting an electron pair. Because electrophiles accept electrons, they are Lewis acids. Most electrophiles are positively charged, have an atom that carries a partial positive charge, or have an atom that does not have an octet of electrons.
The diazogroup is an organic moiety consisting of two linked nitrogen atoms (azo) at the terminal position. Overall charge neutral organic compounds containing the diazo group bound to a carbon atom are called diazo compounds or diazoalkanes and are described by the general structural formula R2C=N+=N–. The simplest example of a diazo compound is diazomethane, CH2N2. Diazo compounds (R2C=N2) should not be confused with azo compounds of the type R-N=N-R or with diazonium compounds of the type R-N2+.
Organopalladium chemistry is a branch of organometallic chemistry that deals with organic palladium compounds and their reactions. Palladium is often used as a catalyst in the reduction of alkenes and alkynes with hydrogen. This process involves the formation of a palladium-carbon covalent bond. Palladium is also prominent in carbon-carbon coupling reactions, as demonstrated in tandem reactions.
The Sandmeyer reaction is a chemical reaction used to synthesize aryl halides from aryl diazonium salts using copper salts as reagents or catalysts. It is an example of a radical-nucleophilic aromatic substitution. The Sandmeyer reaction provides a method through which one can perform unique transformations on benzene, such as halogenation, cyanation, trifluoromethylation, and hydroxylation.
Diazonium compounds or diazonium salts are a group of organic compounds sharing a common functional group R−N+
2X−
where R can be any organic group, such as an alkyl or an aryl, and X is an inorganic or organic anion, such as a halogen.
The Curtius rearrangement, first defined by Theodor Curtius in 1885, is the thermal decomposition of an acyl azide to an isocyanate with loss of nitrogen gas. The isocyanate then undergoes attack by a variety of nucleophiles such as water, alcohols and amines, to yield a primary amine, carbamate or urea derivative respectively. Several reviews have been published.
Nucleophilic acyl substitution describe a class of substitution reactions involving nucleophiles and acyl compounds. In this type of reaction, a nucleophile – such as an alcohol, amine, or enolate – displaces the leaving group of an acyl derivative – such as an acid halide, anhydride, or ester. The resulting product is a carbonyl-containing compound in which the nucleophile has taken the place of the leaving group present in the original acyl derivative. Because acyl derivatives react with a wide variety of nucleophiles, and because the product can depend on the particular type of acyl derivative and nucleophile involved, nucleophilic acyl substitution reactions can be used to synthesize a variety of different products.
In organic chemistry, the Arndt–Eistert reaction is the conversion of a carboxylic acid to its homologue. Named for the German chemists Fritz Arndt (1885–1969) and Bernd Eistert (1902–1978), the method entails treating an acid chlorides with diazomethane. It is a popular method of producing β-amino acids from α-amino acids.
A carbenium ion is a positive ion with the structure RR′R″C+, that is, a chemical species with a trivalent carbon that bears a +1 formal charge.
The Wolff rearrangement is a reaction in organic chemistry in which an α-diazocarbonyl compound is converted into a ketene by loss of dinitrogen with accompanying 1,2-rearrangement. The Wolff rearrangement yields a ketene as an intermediate product, which can undergo nucleophilic attack with weakly acidic nucleophiles such as water, alcohols, and amines, to generate carboxylic acid derivatives or undergo [2+2] cycloaddition reactions to form four-membered rings. The mechanism of the Wolff rearrangement has been the subject of debate since its first use. No single mechanism sufficiently describes the reaction, and there are often competing concerted and carbene-mediated pathways; for simplicity, only the textbook, concerted mechanism is shown below. The reaction was discovered by Ludwig Wolff in 1902. The Wolff rearrangement has great synthetic utility due to the accessibility of α-diazocarbonyl compounds, variety of reactions from the ketene intermediate, and stereochemical retention of the migrating group. However, the Wolff rearrangement has limitations due to the highly reactive nature of α-diazocarbonyl compounds, which can undergo a variety of competing reactions.
The Schiemann reaction is a chemical reaction in which a primary aromatic amine is transformed to an aryl fluoride via a diazonium tetrafluoroborate intermediate. This reaction is a traditional route to fluorobenzene and some related derivatives, including 4-fluorobenzoic acid.
The Schmidt reaction is an organic reaction in which an azide reacts with a carbonyl derivative, usually a aldehyde, ketone, or carboxylic acid, under acidic conditions to give an amine or amide, with expulsion of nitrogen. It is named after Karl Friedrich Schmidt (1887–1971), who first reported it in 1924 by successfully converting benzophenone and hydrazoic acid to benzanilide. Surprisingly, the intramolecular reaction was not reported until 1991 but has become important in the synthesis of natural products.
A homologation reaction, also known as homologization, is any chemical reaction that converts the reactant into the next member of the homologous series. A homologous series is a group of compounds that differ by a constant unit, generally a (-CH2-) group. The reactants undergo a homologation when the number of a repeated structural unit in the molecules is increased. The most common homologation reactions increase the number of methylene (-CH2-) units in saturated chain within the molecule. For example, the reaction of aldehydes or ketones with diazomethane or methoxymethylenetriphenylphosphine to give the next homologue in the series.
The Kowalski ester homologation is a chemical reaction for the homologation of esters.
An insertion reaction is a chemical reaction where one chemical entity interposes itself into an existing bond of typically a second chemical entity e.g.:
The Buchner–Curtius–Schlotterbeck reaction is the reaction of aldehydes or ketones with aliphatic diazoalkanes to form homologated ketones. It was first described by Eduard Buchner and Theodor Curtius in 1885 and later by Fritz Schlotterbeck in 1907. Two German chemists also preceded Schlotterbeck in discovery of the reaction, Hans von Pechmann in 1895 and Viktor Meyer in 1905. The reaction has since been extended to the synthesis of β-keto esters from the condensation between aldehydes and diazo esters. The general reaction scheme is as follows:
The Danheiser benzannulation is a chemical reaction used in organic chemistry to generate highly substituted phenols in a single step. It is named after Rick Danheiser who developed the reaction.
Trifluoroperacetic acid is an organofluorine compound, the peroxy acid analog of trifluoroacetic acid, with the condensed structural formula CF
3COOOH. It is a strong oxidizing agent for organic oxidation reactions, such as in Baeyer–Villiger oxidations of ketones. It is the most reactive of the organic peroxy acids, allowing it to successfully oxidise relatively unreactive alkenes to epoxides where other peroxy acids are ineffective. It can also oxidise the chalcogens in some functional groups, such as by transforming selenoethers to selones. It is a potentially explosive material and is not commercially available, but it can be quickly prepared as needed. Its use as a laboratory reagent was pioneered and developed by William D. Emmons.