In organic chemistry, the Diels–Alder reaction is a chemical reaction between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene derivative. It is the prototypical example of a pericyclic reaction with a concerted mechanism. More specifically, it is classified as a thermally-allowed [4+2] cycloaddition with Woodward–Hoffmann symbol [π4s + π2s]. It was first described by Otto Diels and Kurt Alder in 1928. For the discovery of this reaction, they were awarded the Nobel Prize in Chemistry in 1950. Through the simultaneous construction of two new carbon–carbon bonds, the Diels–Alder reaction provides a reliable way to form six-membered rings with good control over the regio- and stereochemical outcomes. Consequently, it has served as a powerful and widely applied tool for the introduction of chemical complexity in the synthesis of natural products and new materials. The underlying concept has also been applied to π-systems involving heteroatoms, such as carbonyls and imines, which furnish the corresponding heterocycles; this variant is known as the hetero-Diels–Alder reaction. The reaction has also been generalized to other ring sizes, although none of these generalizations have matched the formation of six-membered rings in terms of scope or versatility. Because of the negative values of ΔH° and ΔS° for a typical Diels–Alder reaction, the microscopic reverse of a Diels–Alder reaction becomes favorable at high temperatures, although this is of synthetic importance for only a limited range of Diels-Alder adducts, generally with some special structural features; this reverse reaction is known as the retro-Diels–Alder reaction.
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.
The Claisen condensation is a carbon–carbon bond forming reaction that occurs between two esters or one ester and another carbonyl compound in the presence of a strong base, resulting in a β-keto ester or a β-diketone. It is named after Rainer Ludwig Claisen, who first published his work on the reaction in 1887.
The Japp–Klingemann reaction is a chemical reaction used to synthesize hydrazones from β-keto-acids and aryl diazonium salts. The reaction is named after the chemists Francis Robert Japp and Felix Klingemann.
Carl Dietrich Harries was a German chemist born in Luckenwalde, Brandenburg, Prussia. He received his doctorate in 1892. In 1900, he married Hertha von Siemens, daughter of the electrical genius Werner von Siemens, and the inventor of one of the earliest ozone generators. In 1904, he moved as full professor to the University of Kiel, where he remained until 1916. During that time he published numerous papers on ozonolysis. His major publication detailing ozonolysis was published in Liebigs Ann. Chem. 1905, 343, 311. Dissatisfied with academic life and having failed to obtain either of two positions at universities, he left academia to become director of research at Siemens and Halske. He died on 3 November 1923 of complications following surgery for cancer.
The Knorr pyrrole synthesis is a widely used chemical reaction that synthesizes substituted pyrroles (3). The method involves the reaction of an α-amino-ketone (1) and a compound containing an electron-withdrawing group α to a carbonyl group (2).
The Reed reaction is a chemical reaction that utilizes light to oxidize hydrocarbons to alkylsulfonyl chlorides. This reaction is employed in modifying polyethylene to give chlorosulfonated polyethylene (CSPE), which noted for its toughness.
Cycloheptatriene (CHT) is an organic compound with the formula C7H8. It is a closed ring of seven carbon atoms joined by three double bonds (as the name implies) and four single bonds. This colourless liquid has been of recurring theoretical interest in organic chemistry. It is a ligand in organometallic chemistry and a building block in organic synthesis. Cycloheptatriene is not aromatic, as reflected by the nonplanarity of the methylene bridge (-CH2-) with respect to the other atoms; however the related tropylium cation is.
Elemicin is a phenylpropene, a natural organic compound, and is a constituent of several plant species' essential oils.
Nikolay Nikolaevich Zinin was a Russian organic chemist.
Chlorobutanol (trichloro-2-methyl-2-propanol) is a preservative, sedative, hypnotic and weak local anesthetic similar in nature to chloral hydrate. It has antibacterial and antifungal properties. Chlorobutanol is typically used at a concentration of 0.5% where it lends long term stability to multi-ingredient formulations. However, it retains antimicrobial activity at 0.05% in water. Chlorobutanol has been used in anesthesia and euthanasia of invertebrates and fishes. It is a white, volatile solid with a camphor-like odor.
Phenylarsonic acid is the chemical compound with the formula C6H5AsO(OH)2, commonly abbreviated PhAsO3H2. This colourless solid is an organic derivative of arsenic acid, AsO(OH)3, where one OH group has been replaced by a phenyl group. The compound is a buffering agent and a precursor to other organoarsenic compounds, some of which are used in animal nutrition, e.g. 4-hydroxy-3-nitrobenzenearsonic acid.
Heinrich Limpricht was a German chemist. Limpricht was a pupil of Friedrich Wöhler; he worked on the chemistry of furans and pyrroles, discovering furan in 1870.
The Glaser coupling is a type of coupling reaction. It is by far the oldest acetylenic coupling and is based on cuprous salts like copper(I) chloride or copper(I) bromide and an additional oxidant like oxygen. The base in its original scope is ammonia. The solvent is water or an alcohol. The reaction was first reported by Carl Andreas Glaser in 1869. He suggested the following process for his way to diphenylbutadiyne:
Otto Dimroth was a German chemist. He is known for the Dimroth rearrangement, as well as a type of condenser with an internal double spiral, the Dimroth condenser.
The Rosenmund–von Braun synthesis is an organic reaction in which an aryl halide reacts with cuprous cyanide to yield an aryl nitrile.
The Dimroth rearrangement is a rearrangement reaction taking place with certain 1,2,3-triazoles where endocyclic and exocyclic nitrogen atoms switch place. This organic reaction was discovered in 1909 by Otto Dimroth.
Spiropentane is a hydrocarbon with formula C5H8. It is the simplest spiro-connected cycloalkane, a triangulane. It took several years after the discovery in 1887 until the structure of the molecule was determined. According to the nomenclature rules for spiro compounds, the systematic name is spiro[2.2]pentane. However, there can be no constitutive isomeric spiropentanes, hence the name is unique without brackets and numbers.
Heinrich August Bernthsen was a German chemist who was among the first to synthesize and study the structures of methylene blue and phenothiazine.
Jakob Edmund Speyer was a high-ranking German university lecturer and chemist of Jewish descent. He was persecuted during the National Socialist era, losing his profession and his livelihood. In 1942, he was deported to the Lodz ghetto, where he died shortly after.
