Pyridine is a basic heterocyclic organic compound with the chemical formula C5H5N. It is structurally related to benzene, with one methine group (=CH−) replaced by a nitrogen atom (=N−). It is a highly flammable, weakly alkaline, water-miscible liquid with a distinctive, unpleasant fish-like smell. Pyridine is colorless, but older or impure samples can appear yellow, due to the formation of extended, unsaturated polymeric chains, which show significant electrical conductivity. The pyridine ring occurs in many important compounds, including agrochemicals, pharmaceuticals, and vitamins. Historically, pyridine was produced from coal tar. As of 2016, it is synthesized on the scale of about 20,000 tons per year worldwide.
Pyrrole is a heterocyclic, aromatic, organic compound, a five-membered ring with the formula C4H4NH. It is a colorless volatile liquid that darkens readily upon exposure to air. Substituted derivatives are also called pyrroles, e.g., N-methylpyrrole, C4H4NCH3. Porphobilinogen, a trisubstituted pyrrole, is the biosynthetic precursor to many natural products such as heme.
Furan is a heterocyclic organic compound, consisting of a five-membered aromatic ring with four carbon atoms and one oxygen atom. Chemical compounds containing such rings are also referred to as furans.
Imidazole (ImH) is an organic compound with the formula C3N2H4. It is a white or colourless solid that is soluble in water, producing a mildly alkaline solution. In chemistry, it is an aromatic heterocycle, classified as a diazole, and has non-adjacent nitrogen atoms in meta-substitution.
In organic chemistry, arynes and benzynes are a class of highly reactive chemical species derived from an aromatic ring by removal of two substituents. Arynes are examples of didehydroarenes, although 1,3- and 1,4-didehydroarenes are also known. Arynes are examples of alkynes under high strain.
Thiazole, or 1,3-thiazole, is a 5-membered heterocyclic compound that contains both sulfur and nitrogen. The term 'thiazole' also refers to a large family of derivatives. Thiazole itself is a pale yellow liquid with a pyridine-like odor and the molecular formula C3H3NS. The thiazole ring is notable as a component of the vitamin thiamine (B1).
The Hofmann rearrangement is the organic reaction of a primary amide to a primary amine with one less carbon atom. The reaction involves oxidation of the nitrogen followed by rearrangement of the carbonyl and nitrogen to give an isocyanate intermediate. The reaction can form a wide range of products, including alkyl and aryl amines.
The Larock indole synthesis is a heteroannulation reaction that uses palladium as a catalyst to synthesize indoles from an ortho-iodoaniline and a disubstituted alkyne. It is also known as Larock heteroannulation. The reaction is extremely versatile and can be used to produce varying types of indoles. Larock indole synthesis was first proposed by Richard C. Larock in 1991 at Iowa State University.
A nucleophilic aromatic substitution (SNAr) is a substitution reaction in organic chemistry in which the nucleophile displaces a good leaving group, such as a halide, on an aromatic ring. Aromatic rings are usually nucleophilic, but some aromatic compounds do undergo nucleophilic substitution. Just as normally nucleophilic alkenes can be made to undergo conjugate substitution if they carry electron-withdrawing substituents, so normally nucleophilic aromatic rings also become electrophilic if they have the right substituents.
Phenylacetylene is an alkyne hydrocarbon containing a phenyl group. It exists as a colorless, viscous liquid. In research, it is sometimes used as an analog for acetylene; being a liquid, it is easier to handle than acetylene gas.
The ANRORC mechanism in organic chemistry describes a special type of substitution reaction. ANRORC stands for Addition of the Nucleophile, Ring Opening, and Ring Closure in nucleophilic attack on ring systems and it helps to explain product formation and distribution in some nucleophilic substitutions especially in heterocyclic compounds. It is widely used in medicinal chemistry.
Sulfolene, or butadiene sulfone is a cyclic organic chemical with a sulfone functional group. It is a white, odorless, crystalline, indefinitely storable solid, which dissolves in water and many organic solvents. The compound is used as a source of butadiene.
The Chichibabin reaction is a method for producing 2-aminopyridine derivatives by the reaction of pyridine with sodium amide. It was reported by Aleksei Chichibabin in 1914. The following is the overall form of the general reaction:
The Chichibabin pyridine synthesis is a method for synthesizing pyridine rings. The reaction involves the condensation reaction of aldehydes, ketones, α,β-Unsaturated carbonyl compounds, or any combination of the above, with ammonia. It was reported by Aleksei Chichibabin in 1924. Methyl-substituted pyridines, which show widespread uses among multiple fields of applied chemistry, are prepared by this methodology.
The Gould–Jacobs reaction is an organic synthesis for the preparation of quinolines and 4‐hydroxyquinoline derivatives. The Gould–Jacobs reaction is a series of reactions. The series of reactions begins with the condensation/substitution of an aniline with alkoxy methylenemalonic ester or acyl malonic ester, producing anilidomethylenemalonic ester. Then through a 6 electron cyclization process, 4-hydroxy-3-carboalkoxyquinoline is formed, which exist mostly in the 4-oxo form. Saponification results in the formation of an acid. This step is followed by decarboxylation to give 4-hydroxyquinoline. The Gould–Jacobs reaction is effective for anilines with electron‐donating groups at the meta‐position.
In nitrile reduction a nitrile is reduced to either an amine or an aldehyde with a suitable chemical reagent.
2-Aminopyridine is an organic compound with the formula H2NC5H4N. It is one of three isomeric aminopyridines. It is a colourless solid that is used in the production of the drugs piroxicam, sulfapyridine, tenoxicam, and tripelennamine. It is produced by the reaction of sodium amide with pyridine, the Chichibabin reaction.
The Birch reduction is an organic reaction that is used to convert arenes to 1,4-cyclohexadienes. The reaction is named after the Australian chemist Arthur Birch and involves the organic reduction of aromatic rings in an amine solvent with an alkali metal and a proton source. Unlike catalytic hydrogenation, Birch reduction does not reduce the aromatic ring all the way to a cyclohexane.
In organic chemistry, the hexadehydro-Diels–Alder (HDDA) reaction is an organic chemical reaction between a diyne and an alkyne to form a reactive benzyne species, via a [4+2] cycloaddition reaction. This benzyne intermediate then reacts with a suitable trapping agent to form a substituted aromatic product. This reaction is a derivative of the established Diels–Alder reaction and proceeds via a similar [4+2] cycloaddition mechanism. The HDDA reaction is particularly effective for forming heavily functionalized aromatic systems and multiple ring systems in one synthetic step.
In organic chemistry, thienothiophene is any of several compounds consisting of two fused thiophene rings. They have the molecular formula C6H4S2. Three constitutional isomers have been synthesized: thieno[3,2-b]thiophene, thieno[2,3-b]thiophene, and thieno[3,4-b]thiophene. Other isomers feature S(IV) and are less stable. Thieno[2,3-b]thiophene was the first member of the series to be isolated. It was obtained in very low yield upon heating citric acid, a source of a six-carbon linear chain, with P4S10. More efficient syntheses of this and the other two stable thienothiophenes involve cyclization reactions of substituted thiophenes.
