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Friedländer Synthesis
The Friedländer synthesis is a chemical reaction of 2-aminobenzaldehydes with ketones to form quinoline derivatives. It is named after German chemist Paul Friedländer (1857–1923). This reaction has been catalyzed by trifluoroacetic acid, toluenesulfonic acid, iodine, and Lewis acids. Several reviews have been published. Mechanism Two viable reaction mechanisms exist for this reaction. In the first mechanism 2-amino substituted carbonyl compound 1 and carbonyl compound 2 react in a rate-limiting step to aldol adduct 3. This intermediate loses water in an elimination reaction to unsaturated carbonyl compound 4 and then loses water again in imine formation to quinoline 7. In the second mechanism the first step is Schiff base formation to 5 followed by Aldol reaction to 6 and elimination to 7. : The Pfitzinger reaction and the Niementowski quinoline synthesis are variations of the Friedländer reaction. See also * Doebner-Miller reaction *Povarov reaction *Skraup reaction ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paul Friedländer (chemist)
Paul Friedländer (29 August 1857 in Königsberg – 4 September 1923 in Darmstadt) was a German chemist best known for his research on derivates of indigo (for example thioindigo) and isolation of Tyrian purple from ''Murex brandaris''. Life and work Paul Friedländer was born as son of Ludwig Friedländer in Königsberg in 1857. The chemist Carl Gräbe was a regular guest of his father; thus after finishing the gymnasium, Friedländer studied chemistry in Königsberg in the laboratories of Gräbe. Later he studied at the Strasbourg and Munich where he assisted Adolf von Baeyer. He received his PhD for the work with Baeyer and completed his habilitation in 1883. He left the well-equipped laboratories of Baeyer in Munich in 1884 to work in the small company K. Oehler in Offenbach. In 1888, he became professor at the University of Karlsruhe. During a visit at his parents in Königsberg, he got engaged and married Martha Kobligk; they had three daughters. Although he liked stayi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rate-limiting Step
In chemical kinetics, the overall rate of a reaction is often approximately determined by the slowest step, known as the rate-determining step (RDS or RD-step or r/d step) or rate-limiting step. For a given reaction mechanism, the prediction of the corresponding rate equation (for comparison with the experimental rate law) is often simplified by using this approximation of the rate-determining step. In principle, the time evolution of the reactant and product concentrations can be determined from the set of simultaneous rate equations for the individual steps of the mechanism, one for each step. However, the analytical solution of these differential equations is not always easy, and in some cases numerical integration may even be required. The hypothesis of a single rate-determining step can greatly simplify the mathematics. In the simplest case the initial step is the slowest, and the overall rate is just the rate of the first step. Also, the rate equations for mechanisms with a s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Condensation Reactions
In organic chemistry, a condensation reaction is a type of chemical reaction in which two molecules are combined to form a single molecule, usually with the loss of a small molecule such as water. If water is lost, the reaction is also known as a dehydration synthesis. However other molecules can also be lost, such as ammonia, ethanol, acetic acid and hydrogen sulfide. The addition of the two molecules typically proceeds in a step-wise fashion to the addition product, usually in equilibrium, and with loss of a water molecule (hence the name condensation). The reaction may otherwise involve the functional groups of the molecule, and is a versatile class of reactions that can occur in acidic or basic conditions or in the presence of a catalyst. This class of reactions is a vital part of life as it is essential to the formation of peptide bonds between amino acids and to the biosynthesis of fatty acids. Many variations of condensation reactions exist. Common examples include the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Skraup Reaction
The Skraup synthesis is a chemical reaction used to synthesize quinolines. It is named after the Czech chemist Zdenko Hans Skraup (1850-1910). In the archetypal Skraup reaction, aniline is heated with sulfuric acid, glycerol, and an oxidizing agent such as nitrobenzene to yield quinoline. In this example, nitrobenzene serves as both the solvent and the oxidizing agent. The reaction, which otherwise has a reputation for being violent, is typically conducted in the presence of ferrous sulfate. Arsenic acid Arsenic acid or trihydrogen arsenate is the chemical compound with the formula . More descriptively written as , this colorless acid is the arsenic analogue of phosphoric acid. Arsenate and phosphate salts behave very similarly. Arsenic acid as ... may be used instead of nitrobenzene and the former is better since the reaction is less violent. See also * Bischler-Napieralski reaction * Doebner-Miller reaction References {{DEFAULTSORT:Skraup Reaction Condensatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Povarov Reaction
The Povarov reaction is an organic reaction described as a formal cycloaddition between an aromatic imine and an alkene. The imine in this organic reaction is a condensation reaction product from an aniline type compound and a benzaldehyde type compound. The alkene must be electron rich which means that functional groups attached to the alkene must be able to donate electrons. Such alkenes are enol ethers and enamines. The reaction product in the original Povarov reaction is a quinoline. Because the reactions can be carried out with the three components premixed in one reactor it is an example of a multi-component reaction. : Reaction mechanism The reaction mechanism for the Povarov reaction to the quinoline is outlined in ''scheme 1''. In step one aniline and benzaldehyde react to the Schiff base in a condensation reaction. The Povarov reaction requires a Lewis acid such as boron trifluoride to activate the imine for an electrophilic addition of the activated alkene. This reaction ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Niementowski Quinoline Synthesis
The Niementowski quinoline synthesis is the chemical reaction of anthranilic acids and ketones (or aldehydes) to form γ-hydroxyquinoline derivatives. Overview In 1894, Niementowski reported that 2-phenyl-4-hydroxyquinoline was formed when anthranilic acid and acetophenone were heated to 120–130 °C. He later found that at higher heat, 200 °C, anthranilic acid and heptaldehyde formed minimal yields of 4-hydroxy-3-pentaquinoline.Hartz, pp. 376–384 Several reviews have been published. Variations The temperatures required for this reaction make it less popular than other quinoline synthetic procedures. However, variations have been proposed to make this a more pragmatic and useful reaction. Adding phosphorus oxychloride to the reaction mixture mediates a condensation to make both isomers of an important precursor to an important α1-adrenoreceptor antagonist. When the 3 position of an arylketone is substituted, it has been shown that a Niementowski-type reaction wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pfitzinger Reaction
The Pfitzinger reaction (also known as the Pfitzinger-Borsche reaction) is the chemical reaction of isatin with base and a carbonyl compound to yield substituted quinoline-4-carboxylic acids. Several reviews have been published. Reaction mechanism The reaction of isatin with a base such as potassium hydroxide hydrolyses the amide bond to give the keto-acid 2. This intermediate can be isolated, but is typically not. A ketone (or aldehyde) will react with the aniline to give the imine (3) and the enamine (4). The enamine will cyclize and dehydrate to give the desired quinoline (5). Variations Halberkann variant Reaction of ''N''-acyl isatins with base gives 2- hydroxy-quinoline-4-carboxylic acids. See also *Camps quinoline synthesis *Friedländer synthesis *Niementowski quinazoline synthesis *Talnetant, Cinchocaine Cinchocaine (INN/ BAN) or dibucaine (USAN) is an amide local anesthetic. Among the most potent and toxic of the long-acting local anesthetics, current use of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schiff Base
In organic chemistry, a Schiff base (named after Hugo Schiff) is a compound with the general structure ( = alkyl or aryl, but not hydrogen). They can be considered a sub-class of imines, being either secondary ketimines or secondary aldimines depending on their structure. The term is often synonymous with azomethine which refers specifically to secondary aldimines (i.e. where R' ≠H). A number of special naming systems exist for these compounds. For instance a Schiff base derived from an aniline, where is a phenyl or a substituted phenyl, can be called an ''anil'', while bis-compounds are often referred to as salen-type compounds. The term Schiff base is normally applied to these compounds when they are being used as ligands to form coordination complexes with metal ions. Such complexes occur naturally, for instance in corrin, but the majority of Schiff bases are artificial and are used to form many important catalysts, such as Jacobsen's catalyst. Synthesis Schiff ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Imine
In organic chemistry, an imine ( or ) is a functional group or organic compound containing a carbon–nitrogen double bond (). The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bonds. Imines are common in synthetic and naturally occurring compounds and they participate in many reactions. Structure For ketimines and aldimines, respectively, the five core atoms (C2C=NX and C(H)C=NX, X = H or C) are coplanar. Planarity results from the sp2-hybridization of the mutually double-bonded carbon and the nitrogen atoms. The C=N distance is 1.29-1.31 Å for nonconjugated imines and 1.35 Å for conjugated imines. By contrast, C-N distances in amines and nitriles are 1.47 and 1.16 Å, respectively. Rotation about the C=N bond is slow. Using NMR spectroscopy, both E- and Z-isomers of aldimines have been detected. Owing to steric effects, the E isomer is favored. Nomenclature and classification The term "imine" was coine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Α,β-unsaturated Carbonyl Compound
In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containing a carbonyl group is often referred to as a carbonyl compound. The term carbonyl can also refer to carbon monoxide as a ligand in an inorganic or organometallic complex (a metal carbonyl, e.g. nickel carbonyl). The remainder of this article concerns itself with the organic chemistry definition of carbonyl, where carbon and oxygen share a double bond. Carbonyl compounds In organic chemistry, a carbonyl group characterizes the following types of compounds: Other organic carbonyls are urea and the carbamates, the derivatives of acyl chlorides chloroformates and phosgene, carbonate esters, thioesters, lactones, lactams, hydroxamates, and isocyanates. Examples of inorganic carbonyl compounds are carbon dioxide and carbonyl sulfide. A sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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