Showing papers in "Organic Reactions in 2011"
TL;DR: In this article, the authors defined the Knoevenagel condensation as the reaction between an aldehyde or ketone or any compound having an active methylene group, brought about by an organic base or ammonia and their salts.
Abstract: Knoevenagel's first papers in this field were concerned with the condensation of formaldehyde with diethyl malonate and with ethyl benzoylacetate. The catalyst was ethylamine. A number of other aldehydes were reported to condense similarly with diethyl malonate, ethyl benzoylacetate, ethyl benzoylpyruvate, and acetylacetone under the influence of various primary and secondary amines. In 1896, Knoevenagel reported benzaldehyde with ethyl aceoacetate condensed at room temperature in the presence of piperdine to give a bis compound, but that when the reaction was run in a freezing mixture, the product was acetoacetate. For the purposes of this chapter, the Knoevenagel condensation is defined as the reaction between an aldehyde or ketone or any compound having an active methylene group, brought about by an organic base or ammonia and their salts.
Keywords:
Knoevenagel condensations;
decarboxylation;
malonic acid;
active methylene component;
stereochemical aspects;
cyanoacetic acid;
ketones;
derivatives. caatalysts;
experimental conditions
125 citations
TL;DR: The aldol condensation as discussed by the authors is defined as the condensation of an aromatic aldehyde or ketone usually in the presence of a basic catalyst, and has been applied to many other condensations involving the reaction of an α-ketone or β-aldol.
Abstract: The aldol condensation takes its name from aldol (3-hydroxybutanal) a name introduced by Wurtz who first prepared the beta-hydroxy aldehyde from acetaldehdye in 1872. The aldol condensation includes reactions producing beta-hydroxy aldehydes or beta-hydroxy ketones by self condensations or mixed condensations of aldehydes and ketones as well as reactions leading to alpha, beta-unsaturated aldehydes or alpha,beta-unsaturated ketones formed by dehydration of intermediate beta-aldols or beta-ketals. The Claisen-Schmidt condensation is most often taken to be the condensation of an aromatic aldehyde or ketone usually in the presence of a basic catalyst. The term aldol condensation has also been applied to many other condensations involving the reaction of an aldehyde or ketone. These condenations are discussed. The present review includes examples that are solely condensation reactions of aldehydes and ketones.
Keywords:
aldol condensation;
catalysis;
condensation;
aldehydes;
ketones;
intramolecular condensations;
stereochemistry;
amines;
acids;
bases;
self-condensation;
mixed condensation;
acyclic ketones;
alicyclic ketones;
alkyl aryl ketones;
dialdehydes;
diketones;
keto aldehydes
58 citations
[...]
TL;DR: The Mannich reaction consists in the condensation of ammonia or a primary or secondary amines, usually as the hydrochloride, with formaldehyde and a compound containing at least one hydrogen atom of pronounced reactivity as discussed by the authors.
Abstract: The Mannich reaction consists in the condensation of ammonia or a primary or secondary amines, usually as the hydrochloride, with formaldehyde and a compound containing at least one hydrogen atom of pronounced reactivity. The essential feature of the reaction is the replacement of the active hydrogen atom by an aminomethyl or substituted aminomethyl group. The product from acetophenone, formaldehyde, and a secondary amine salt is an example. The product to be expected from a Mannich reaction involving an ammonium salt is a primary amine. The mechanism of the Mannich reaction has not been established.
Keywords:
Mannich reaction;
secondary amines;
primary amines;
ammonia;
ketones;
aldehydes;
acids;
esters;
phenol;
picolines;
acetylenes;
quinaldines
53 citations
TL;DR: A modified Skraup synthesis in which a substituted acrolein or a vinyl ketone is used in place of glycerol is described in this article. But it is not known whether the substitutions were originally present in the aromatic amine.
Abstract: Konigs first synthesized quinoline in 1879 by passing allylaniline over heated litharge. Shortly after he prepared quinoline by heating the condensation product of aniline and acrolein, thus anticipating the classical Skraup synthesis. This synthesis involves a series of reactions brought about by heating a primary aromatic amine, in which at least one position ortho to the amino group is unsubstituted, with glycerol, sulfuric acid, and an oxidizing agent. The product is a quinoline containing only those substituents that were originally present in the aromatic amine. Quinolines substituted in the hetero ring may be obtained by a modified Skraup synthesis in which a substituted acrolein or a vinyl ketone is used in place of glycerol.
Keywords:
Skraup synthesis;
quinolines;
aroquinolines;
orientation;
nitroquinolines;
dimethylquinolines;
oxidizing agents;
experimental conditions
38 citations
TL;DR: A survey of the types of carbonyl components and acid anhydride salt combinations that can be used and of the yields obtained under favorable conditions can be found in this article, where the authors describe the Perkin reaction as the condensation of an acid and dihydride-salt combination.
Abstract: In 1868, W. H. Perkin described a synthesis of coumarin by heating the sodium salt of salicyaldehyde with acetic acid. Further study led to a new discovery for preparing cinnamic acid and its analogs by means of a synthesis of very general application, which became know as the Perkin reaction. In the course of study of unsaturated acids, Fittig made several important contributions to the mechanism of the Perkin reaction. Many studies have been made regarding this reaction and are described. The Perkin reaction may be regarded essential as the condensation of a carbonyl component A and an acid and dihydride-salt combination B. The discussion here is a survey of the types of carbonyl components and acid anhydride salt combinations that can be used and of the yields obtained under favorable conditions.
Keywords:
Perkin reaction;
carbonyl compounds;
cinnamic acids;
unsaturated acids;
benzaldehyde;
acid components;
laboratory procedures;
cinnamic acid derivatives;
experimental conditions
38 citations
36 citations
TL;DR: In this article, the metal-catalyzed hydrocyanation of alkenes or alkynes was studied, where Acetone cyanohydrin and trimethylsilyl cyanide (TMSCN) were used for the in-situ generation of HCN.
Abstract: Hydrogen cyanide is an abundantly available feedstock that is useful for the synthesis of organonitrile intermediates, which serve as precursors for amines, amides, isocyanates, carboxylic acid, and esters. Many of these compounds are used in the manufacture of polymers, agrichemicals, cosmetics, and pharmaceuticals. Hydrogen cyanide itself is relatively unreactive, but in the presence of a catalyst HCN adds to carbonyl compounds, alkenes, and alkynes offering a direct and economical way to such organonitrile intermediates.
This chapter focuses primarily on the metal-catalyzed hydrocyanation of alkenes or alkynes. Acetone cyanohydrin and trimethylsilyl cyanide (TMSCN), both commercially available reagents, can be used for the in-situ generation of HCN. In some transition-metal catalyzed additions, TMSCN acts as a surrogate for HCN, giving products where the TMS group replaces the hydrogen. Preparatively, these reagents provide some advantages since the handling of toxic HCN is avoided. Reactions of these reagents are included here under appropriate substrate and direct comparison of yield and selectivity can be made.
Keywords:
Hydrocyanation;
Alkenes;
Alkynes;
Asymmetric hydrocyanation;
Metal catalysts;
Norbornene;
Vinylarenes;
1,3-Dienes;
Safety;
Hydrogen cyanide;
Conjugate addition;
Mechanisms;
Experimental procedures
31 citations
[...]
TL;DR: Wittig and Geissler as discussed by the authors used the Wittig reaction for the synthesis of methylene phosphoranes and showed that it can yield 1,1-diphenylethylene and triphenylphosphine oxide in almost quantitative yield.
Abstract: In 1953 Wittig and Geissler found that reaction of benzophenone with methylenetriphenylphosphorane gave 1,1-diphenylethylene and triphenylphosphine oxide in almost quantitative yield; the phosphine had been prepared from triphenylmethylphosphonium bromide and phenyl lithium. The discovery led to the development of a new method for the synthesis of olefins, under the name Wittig reaction. One advantage of this new method is that the carbonyl group is replaced specifically by a carbon-carbon double bond without the formation of isomeric olefins. In contrast, the older method of converting carbonyl compounds to olefins using the Grignard reaction usually give a mixture of isomeric olefins. Another advantage is the Wittig reaction is carried out under mild conditions. Discussions of modern techniques for the preparation of methylene phosphoranes are included in this review.
Keywords:
wittig reaction;
alkylidene triphenylphosphoranes;
alkyl-substituted olefins;
aryl-substituted olefins;
unsaturated carbonyl compounds;
vinyl halides;
vinyl ethers;
natural products;
side reactions;
vitamins;
steroids;
experimental conditions
29 citations
TL;DR: In this article, the authors present a survey of the Smiles rearrangements, which may be characterized as intramolecular displacements at aromatic rings initiated by nucleophilic centers located two or three atoms distant from the functional group which is displaced.
Abstract: In 1894, Henriques reported that bis(2-hydroxy-1-naphthyl) sulfide was converted to an isomeric dibasic substance by treatment with alkaline ferricyanide and a subsequent reduction of the intermediate obtained. Hinsberg carried out a similar sequence of reactions with bis(2-hydroxy 1 naphthyl) sulfone. The structures of the isomeric products of the two series were established by Smiles who recognized the occurrence of a novel intramolecular nucleophilic rearrangement.
This chapter surveys the reactions, which because of the extensive work of Smiles, have been called Smiles rearrangements. They may be characterized as intramolecular displacements at aromatic rings initiated by nucleophilic centers located two or three atoms distant from the functional group which is displaced.
Keywords:
smiles rearrangements;
aromatic systems;
aromatic ring;
activation;
reverse rearrangements;
pyridyl systems;
acidity;
electronic effects;
steric effects;
phenazine;
phenothiazine;
phenoxazine;
experimental procedures
27 citations
[...]
TL;DR: The original scope of the Michael condensation has been extended to include addends and acceptors activated by groups other than carbonyl and carboxalkoxy as mentioned in this paper, and a wider scope is encompassed in this survey.
Abstract: The Michael condensation in its original scope is the addition of an addend or donor containing an alpha-hydrogen atom in the system OCCH to a carbon-carbon double bond that forms part of a conjugated system of the general formula CCCO in an acceptor The condensation takes place under the influence of alkaline reagents, typically alkali metal alkoxides The range of addends is very broad Typical acceptors are alpha, beta-unsaturated aldehydes, keotnes, and acid derivatives As an extension of the original scope, the Michael condensation has come to be understood to include addends and acceptors activated by groups other than carbonyl and carboxalkoxy The wider scope is encompassed in this survey
Keywords:
Michael reaction;
side reaction;
adduct;
bridged intermediates;
cyclopropane derivatives;
Michael condensation;
ketones;
esters;
cycloalkanones;
cycloalkenes;
Robinson's modification;
aromatic rings systems;
rings;
pyrroles;
piperidines;
pyrrolizidines;
amino salts;
experimental conditions
27 citations
TL;DR: Organosilicon functions possess many properties that make them ideal donors of organic groups in cross-coupling reactions as mentioned in this paper, and through the addition of an appropriate silicophilic Lewis base, an in situ pentacoordinate silane can effectively transfer an organic group.
Abstract: Organosilicon functions possess many properties that make them ideal donors of organic groups in cross-coupling reactions. Through the addition of an appropriate silicophilic Lewis base, an in situ pentacoordinate silane can effectively transfer an organic group. This feature allows for the rapid development of silicon cross-coupling methods that continue today. Organosilicon-based cross-coupling has now become a practical, viable, and in some cases, superior compared with organoboron,-zinc,-tin couplings. The unique properties of organosilicon compounds provide a number of distinct advantages to their use as donors in transition-metal catalyzed cross-coupling reactions: 1, silicon moieties can be introduced into organic substrates by many general and high-yielding methods for the construction of silicon carbon bonds; 2, organosilicon reagents are chemically robust and allow isolation and purification of products and are compatible with many functional groups; 3, silicon-containing by-products of the coupling are of low molecular weight, are nontoxic, and are easily removed from the reaction mixture; 4, a number of mild methods are available.
This chapter presents a thorough overview of the various combinations of transferable groups and organic electrophiles. The scope is limited to the combination of silicon-bearing nucleophiles with halo or related electrophiles under catalysis by palladium or nickel complexes wherein the silyl halide is lost.
Keywords:
Cross coupling;
Organosilicon compounds;
Alkenylsilanes;
Allylsilanes;
Benzylsilanes;
Halosilanes;
Silanols;
Silanolates;
Alkoxysilanes;
Polysiloxanes;
Disiloxanes;
Cyclic silyl ethers;
Ruthenium catalysts;
Palladium;
Ligands;
Solvents;
Fluoride;
Mechanisms;
Enantioselectivity;
Experimental procedures
TL;DR: The reaction in which two aldehyde groups are transformed into the corresponding hydroxyl and carbonyl functions, existing separately or in combination as an ester, has been termed the Cannizzaro reaction as mentioned in this paper.
Abstract: The reaction in which two aldehyde groups are transformed into the corresponding hydroxyl and carbonyl functions, existing separately or in combination as an ester, has been termed the Cannizzaro reaction. Here the discussion is restricted to the dismutation of two similar aldehyde groups into the corresponding alcohol and carboxylic salt function by means of aqueous or alcoholic and alkali. The conversion of benzaldehyde into a mixture of benzyl alcohol and sodium benzoate is an example.
Keywords:
Cannizzaro reaction;
aliphatic aldehydes;
aromatic aldheydes;
heterocyclic aldehydes;
crossed Cannizzaro reaction;
experimental conditions
TL;DR: The Pictet-Spengler reaction as mentioned in this paper is a special example of the Mannich reaction and is used to synthesize tetrahydroisoquinolone and carbolines.
Abstract: The Pictet-Spengler reaction, in its simplest form, consists in the condensation of a beta-arylethylamine with a carbonyl compound to yield a tetrahydroisoquinolone and is a special example of the Mannich reaction. The condensation of phenethylamine with methylal in concentrated hydrochloric acid to form 1,2,3,4-tetrahydroisoquinoline was achieved in 1911 by Pictet and Spengler. Their reaction has been applied to the synthesis of other ring systems. The theory that proteins are the parent substances of alkaloids was tested by Pictet, who heated casein with methylal and hydrochloric acid, obtaining a mixture of pyridine and isoquinoline bases. Most of the products were not definitely identified.
Keywords:
Pictet-Spengler synthesis;
tetrahydroisoquinolines;
cyclization;
aromatic nucleus;
carbonyl component;
side reactions;
condensing agents;
carbolines;
experimental conditions
TL;DR: In an attempt to prepare an azo ester by coupling benzendiazonium chloride with ethyl-2-methylacetoacetate, Japp and Klingemann obtained a product, which was soon recognized as the phenylhydrazone of ethyl pyruvate as discussed by the authors.
Abstract: In an attempt to prepare an azo ester by coupling benzendiazonium chloride with ethyl-2-methylacetoacetate, Japp and Klingemann obtained a product, which was soon recognized as the phenylhydrazone of ethyl pyruvate. It thus appears that the acetyl group is displaced, actually the coupling product was unstable under the conditions of its formation, undergoing hydrolytic scission of the acetyl group and rearrangement of the azo structure. It was later discovered that, if the substituted acetoacetic ester was saponified and the cocoupling carried out on the sodium salt, the carboxylic function rather than the acetyl group, was lost and the product isolated was the phenylhydrazone of biacetyl. This reaction was extended to other systems containing methinyl groups.
Keywords:
Japp-Klingmann reaction;
Ethyl pyruvate o-nitrophenylhydrazone;
1,2-Cyckllohexanedione monophenyhydrazone;
Cleavage;
Acyl group;
Decarboxylation
TL;DR: The Simonis reaction is a variation of the Pechmann reaction and is considered in this chapter as mentioned in this paper, but it is not a variant of the Simonis condensing agent.
Abstract: H. v. Pechman found that coumarin derivatives are formed when malic acid or beta-ketonic esters are condensed with phenols in the presence of concentrated sulfuric acid. This reaction is commonly known s the Pechmann reaction. It has found extensive use. Simonis and co-workers used phosphorus pentaoxide as the condensing agent in place of sulfuric acid and demonstrated that with the same reactants chromones rather than coumarins resulted. The condensation of a phenol and beta-ketonic ester in the presence of phosphorus pentaoxide is sometimes called the Simonis reaction, but it is actually a variation of the Pechmann reaction and is considered in this chapter. Other condensing agents that have been used, for example, are phosphorus oxychloride, phosphoric acid, zinc chloride and others. These are discussed in the chapter. By condensing appropriately substituted phenols and beta-ketonic esters, coumarins can be synthesized with substituents either in the benzene nucleus in the heterocyclic ring or both. The course of this reaction depends on three factors; nature of the phenol, of the beta-ketonic ester, and the condensing agent.
Keywords:
Pechmann reaction;
malic acid;
phenols;
ketonic esters;
5-hydroxycoumarin derivatives;
aluminum chloride;
condensing agents;
experimental procedures
TL;DR: The based-promoted rearrangements of quaternary ammonium salts can be divided into two categories as mentioned in this paper : the Somelet-Hayser rearrangement and the Stevens rearrange.
Abstract: The based-promoted rearrangements of quaternary ammonium salts can be divided into two categories. In the Stevens rearrangement one-alkyl group migrates from the quaternary nitrogen group to the alpha carbon atom of a second alkyl group. The Somelet-Hayser rearrangement involves migration to the ortho position of a benzyl quaternary ammonium salt. When structurally feasible, both rearrangements may occur simultaneously although experimental conditions markedly affect the competing pathways.
Keywords:
Sommelet-Hauser rearrangements;
Stevens rearrangements;
quaternary ammonium salts;
competitive rearrangements. experimental conditions
TL;DR: The Reformatsky reaction is the reaction of a carbonyl compound, usually an aldehyde or a ketone, with an alpha-haloester in the presence of zinc metal to furnish, after hydrolysis, a β-hydoxyester as mentioned in this paper.
Abstract: The Reformatsky reaction is the reaction of a carbonyl compound, usually an aldehyde or a ketone, with an alpha-haloester in the presence of zinc metal to furnish, after hydrolysis, a β-hydoxyester. Subsequent dehydration of the hydroxyester is commonly carried out to form an alpha, β-unsaturated ester. This chapter summarizes some of the more important advances in the understanding and use of the Reformatsky reaction since the original chapter was published in volume 1 of this series.
Keywords:
Reformatsky reaction;
side reactions;
stereochemistry;
variations;
zinc;
promoters;
solvents;
two-step procedures;
comparisons with other methods;
experimental procedures
TL;DR: The reaction of p-benzoquinone with acetic acid in the presence of a small quantity of sulfuric acid to give 1,2,4-triacetoxybenzene in 80% yield was described by Thiele and Winter.
Abstract: In 1898, Johannes Thiele described the reaction of p-benzoquinone with acetic acid in the presence of a small quantity of sulfuric acid to give 1,2,4-triacetoxybenzene in 80% yield Later Thiele and Winter described further experiments that showed both 1,2- and 1,4-naphthoquinone gave 1,2,4-triacetoxynaphthalene and that the same product was obtained when sulfuric acid was replaced by zinc chloride Thiele-Winter acetoxylation can be defined as the acid-catalyzed reactions of quinones with acetic acid to give triacetoxy aromatic compounds This reaction has been carried out on a large number of quinones and to this point there has been no review Very little work has been done on the reaction of quinones with anhydrides other than acetic anhydride Results of these studies are summarized Reactions with other anhydrides are discussed
Keywords:
Thiele-Winter acetoxylation;
quinones;
benzoquinones;
naphthoquinones;
anhydride;
triacetates;
butylquinones;
methylquinones;
experimental procedures
TL;DR: The Reformatsky reaction as discussed by the authors is an extension of the reactions of carbonyl compounds with a dialkylzinc or an alkyl-zinc halide, but possesses the advantage that the isolation of the organozinc compound is unnecessary.
Abstract: The reaction which takes place between a carbonyl compound such as an aldehyde, ketone, or an ester, and an alpha-haloester in the presence of zinc is commonly known as the Reformatsky reaction. It represents an extension of the reactions of carbonyl compounds with a dialkylzinc or an alkylzinc halide, but possesses the advantage that the isolation of the organozinc compound is unnecessary. The process creates a new carbon-carbon linkage and involves the following: Formation of an organozinc halide; addition to the carbonyl group of the aldehyde or ketone, decomposition by dilute acids.
Keywords:
Reformatsky reaction;
side reactions;
halogen compounds;
carbon chain;
arylacetic acids;
beta-ketoesters;
variations;
experimental conditions
TL;DR: The use of aluminum chloride as a catalyst was studied by Thomas as discussed by the authors, who showed that aluminum chloride catalyzes the condensation of alkyl and acyl halides with various aromatic compounds to effect substitution of an alkyyl or acyl group for more or more hydrogen atoms of the aromatic compound.
Abstract: Since the discovery by Friedel and Crafts that aluminum chloride catalyzes the condensation of alkyl and acyl halides with various aromatic compounds to effect substitution of an alkyl or acyl group for more or more hydrogen atoms of the aromatic compound, this reaction has been greatly extended in scope with respect to alkylating or acylating agents and catalysts The use of aluminum chloride as a catalyst was studied by Thomas Aspects of this study appeared in an earlier volume of this series The present discussion is limited to the direct alkyl, cycloalky, or aralkyl residues containing no functional groups into various aromatic compounds under various catalysts, such as eg, aluminum trichloride, zinc dichloride, and hydrogen fluoride The alkylating agents include olefins, highly strained cycloparaffins, polyalkylbenzenes, alkyl halides, alcohols, esters, of inorganic and organic acids, and ethers The aromatic compound may be eg, a hydrocarbon, an aryl chloride, or bromide, a mono-or polyhdrydric phenol or its ether The Friedel-Crafts process is frequently the most useful method for the introduction of an alkyl group
Keywords:
alkylation;
Friedel-Crafts method;
aromatic compounds;
rearrangements;
alkylating agents;
catalysts;
experimental directions
TL;DR: The Diels-Alder reaction consists in an addition of a compound containing a double or triple bond (usually activated by additional unsaturation in the alpha, beta-position) to the 1,4-positions of a conjugated dienes system with the formation of a six-membered ring as discussed by the authors.
Abstract: The Diels-Alder reaction consists in an addition of a compound containing a double or triple bond (usually activated by additional unsaturation in the alpha, beta-position) to the 1,4-positions of a conjugated dienes system with the formation of a six-membered ring, Various dienes systems to dienophiles are described as typical examples of the Diels-Alder reaction. A noteworthy feature of this reaction is the great variety of compounds that may serve as the dienophile. Among the most widely employed dienophiles are maleic anhydride and closely related dicarboxylic acid derivatives.
Keywords:
Diels-Alder reaction;
malic anhydride;
dienophiles;
acyclic compounds;
aromatic compounds;
heterocyclic compounds;
diene analysis;
side reactions;
experimental procedures
TL;DR: The Bischler-Napieralski reaction was introduced by Picet and Gams in this paper, which eliminates the dehydrogenation step of the original reaction by using milder condensing agents.
Abstract: The frequent occurrence of the isoquinoline nucleus in alkaloids has led to considerable interest in the synthesis of isoquinolone derivatives. Many methods have been developed, but only three have enjoyed popularity. One of them, the Bischler-Napieralski reaction is discussed in this chapter. The reaction consists in the cyclodehydration of beta-phenethylamides to 3,4-dihydroisoquinolines by heating to high temperatures with phosphorus pentoxide or anhydrous zinc chloride. Yields were not given for the original reaction, but later studies proved that the yields were low. Modifications using lower temperatures and milder condensing agents improved the reaction. The most important variation was introduced by Picet and Gams, which eliminates the dehydrogenation step. The classical synthesis of papaverine by Pictet and Gams is discussed.
Keywords:
Bischler Napieralski reaction;
3,4-dihydroisoquinolines;
cyclization;
ring closure;
side reactions;
condensing agents;
related compounds
TL;DR: The Leuckart reaction as discussed by the authors is a process for reductive alkylation of ammonia or primary or secondary amines by certain aldehdyes and ketones, it is distinguished by the fact that the reduction is accomplished by formic acid or a derivative of formic acids and should be compared with reductive ALYCLATION discussed elsewhere in this series.
Abstract: The Leuckart reaction is a process for reductive alkylation of ammonia or primary or secondary amines by certain aldehdyes and ketones, It is distinguished by the fact that the reduction is accomplished by formic acid or a derivative of formic acid and should be compared with reductive alkylation discussed elsewhere in this series. The reaction is carried out by heating a mixture of the carbonyl compound and the formic acid salt or formyl derivative of ammonia or the amine. Primary and secondary amines produced in the reaction often are obtained as the formyl derivatives and must be recovered by hydrolysis; tertiary amines are obtained as formate. Modifications of this reaction are discussed.
Keywords:
Leuckart reaction;
formaldehyde;
aldehydes;
ketones;
quinones;
pyrazolone;
oxindole;
ammonium formate;
reductive alkylation. amines;
experimental procedures
TL;DR: In this article, the conventions used in this chapter for the configurations of ketoximes and aldoximes are explained, as well as the procedures used for the rearrangement of a ketoxime to a corresponding amide.
Abstract: The rearrangement of a ketoxime to the corresponding amide was discovered in 1886 by E. Beckmann and is known as the Beckmann rearrangement. The rearrangement is brought about by acids, including Lewis acids. The more common rearranging agents are concentrated sulfuric acid, phosphorus pentachloride in ether, and Beckmann's mixture, hydrogen chloride in a mixture of acetic acid and acetic anhydride. The Beckmann rearrangement is used frequently to determine the structure of ketones, by identification of the acid and amine obtained by hydrolysis of the amide formed by the rearrangement. There is no uniform convention for the designation of the stereochemistry of oximes in the literature. The conventions used in this chapter for the configurations of ketoximes and aldoximes are explained.
Keywords:
Beckmann rearrangement;
ketoximes;
aldoximes;
cleavage;
carbon-nitrogen rearrangements;
oximes;
diketones;
nitrones;
stereochemistry;
mechanisms;
experimental procedures
[...]
TL;DR: The Ritter reaction was first described by Ritter in 1948 and has been extended to the addition of nitriles to a wide variety of compounds capable of forming a carbonium ion and constitutes the only really useful procedure for the preparation of amides of tertiary carbinamines as mentioned in this paper.
Abstract: The formation of N-substituted amides by the addition of nitriles to alkenes in the presence of concentrated sulfuric acid was first described by Ritter in 1948. The reaction has been extended to the addition of nitriles to a wide variety of compounds capable of forming a carbonium ion, and it constitutes the only really useful procedure for the preparation of amides of tertiary carbinamines. In its most general form, the Ritter reaction involves the nucleophilic addition of a nitrile to a carbonium ion in the presence of sulfuric acid. Attention has been given to reactions in which the carbonium ion is generated in sulfuric acid, or less commonly in sulfonic acids, phosphoric acids, or boron trifluoride. For comparison, analogous reactions, which are initiated by a nitrilium ion, formed from a nitrile and a Friedel-Crafts catalyst, have been included in this chapter.
Keywords:
Ritter reaction;
alkanes;
alkenes;
alkadienes;
alcohols;
alkyl chlorides;
aldehydes;
ketones;
unaturated carbonyl compounds;
methylolamides;
carboxylic acids;
esters;
oximes;
heterocyclic syntheses;
related processes;
experimental conditions
[...]
TL;DR: The decomposition of acid azides to isocyanates and nitrogen is known as the Curtius rearrangement The reaction is a preparative method for replacing a carboxyl group by an amino group.
Abstract: The decomposition of acid azides to isocyanates and nitrogen is known as the Curtius rearrangement The reaction is a preparative method for isocyanates, ureas, amides, and amines When coupled with a hydrolytic step, the Curtius rearrangement becomes a practical procedure for replacing a carboxyl group by an amino group The overall process of converting an acid through its azide to an amine is commonly referred to as the Curtius reaction Acid azides are commonly prepared by treating hydrazides in cold, aqueous solution with nitrous acid Azides can be rearranged in inert solvents, from which isocyanates can be isolated in the presence of water or alcohol, which will react with the intermediate to form urethans or ureas
Keywords:
curtius reaction;
monocarboxylic acids;
unsaturated acids;
hydroxy acids;
keto acids;
amino acids;
functional groups;
heterocyclic systems;
azides;
Hofmann reaction;
Schmidt reaction;
related reactions;
experimental procedures
[...]
TL;DR: The Schmidt reaction was first reported by Karl Friedrich Schmidt in 1923 as mentioned in this paper, and it offers a convenient method for the preparation of amines from acids and is known as the Schmidt reaction.
Abstract: The reaction between equimolar quantities of hydrazoic acid and carbonyl compounds in the presence of a strong mineral acid has become known as the Schmidt reaction It offers a convenient method for the preparation of amines from acids. Aldehydes yield nitriles and formyl derivatives of amines, and ketones yield amides. With hydrazoic acid in large excess, aldehdyes and ketones yield substituted tetrazoles. The reaction of carbonyl compounds with hydrazoic acid was first reported by Karl Friedrich Schmidt in 1923.
Keywords:
Schmidt reaction;
hydrazoic acid;
acids;
aldehydes;
ketones;
quinones;
hydrocarbons;
esters;
lactones;
anhydrides;
experimental conditions
TL;DR: Claisen rearrangement was first observed when ethyl O-allylacetonacetate was subjected to distillation at atmospheric pressure in the presence of ammonium chloride.
Abstract: Allyl ethers of enols and phenols undergo rearrangement to C-allyl derivatives when heated to sufficiently high temperatures. The reaction, named after its discoverer (Claisen, 1912) was first observed when ethyl O-allylacetonacetate was subjected to distillation at atmospheric pressure in the presence of ammonium chloride. The allyl ethers of phenols rearrange smoothly at temperatures of about 200°C in the absence of catalysts, Allyl ethers of ortho-disubstituted phenols rearrange to the corresponding p-allyphenols. The only known example of para rearrangement accompanied by inversion is the reaction of alpha-ethylallyl 2-carbomethoxy-6-methylphenyl ether. These rearrangements are discussed in detail.
Keywords:
Claisen rearrangement;
open chain compounds;
ally aryl ethers;
allylphenols;
allyethers;
structural requirements;
side reactions;
experimental conditions
TL;DR: The Zinin reduction is a method for the reduction of nitroarenes by negative divalent sulfur as discussed by the authors, which can be carried out in the laboratory and for plant-scale manufacture of aromatic amines when other reduction media are destructive to sensitive compounds or result in undesirable side reactions.
Abstract: The Zinin reduction is a method for the reduction of nitroarenes by negative divalent sulfur. This versatile reaction can be carried out in the laboratory and for plant-scale manufacture of aromatic amines when other reduction media are destructive to sensitive compounds or result in undesired side reactions. The first reaction, used by Zinin, was to prepare aniline from nitrobenzene. It has been of great importance in the preparation of aromatic amines. Refinements in technique and a better understanding of the reaction mechanism should make this method attractive for the preparation of a variety of amines.
Keywords:
zinin reduction;
nitroarenes;
side reactions;
nitro groups. nitrosoarenes;
arylamines;
azobenzene reduction;
hydrazobenzene;
experimental conditions
TL;DR: In this article, the authors defined reductive alkylation as the process of introducing alkyl groups into ammonia or primary or secondary amine by means of an aldehdye or ketone in the presence of a reducing agent.
Abstract: Reductive alkylation is the term applied to the process of introducing alkyl groups into ammonia or primary or secondary amine by means of an aldehdye or ketone in the presence of a reducing agent. This chapter is limited to those reductive alkylations in which the reducing agent is hydrogen and a catalysts or nascent hydrogen, usually from a metal-acid combination; most of these reductive alkylations have been carried out with hydrogen and a catalyst.
Keywords:
amines;
reductive alkylation;
aldehdyes;
ketones;
ammonia;
Schiff's base;
primary amines;
secondary amines;
tertiary amines;
experimental conditions