The Beckmann rearrangement, named after the German chemist Ernst Otto Beckmann (1853–1923), is a rearrangement of an oxime functional group to substituted amides. The rearrangement has also been successful performed on haloimines and nitrones. Cyclic oximes and haloimines yield lactams.
The Heck reaction is the chemical reaction of an unsaturated halide with an alkene in the presence of a base and a palladium catalyst to form a substituted alkene. It is named after Tsutomu Mizoroki and Richard F. Heck. Heck was awarded the 2010 Nobel Prize in Chemistry, which he shared with Ei-ichi Negishi and Akira Suzuki, for the discovery and development of this reaction. This reaction was the first example of a carbon-carbon bond-forming reaction that followed a Pd(0)/Pd(II) catalytic cycle, the same catalytic cycle that is seen in other Pd(0)-catalyzed cross-coupling reactions. The Heck reaction is a way to substitute alkenes.
In chemistry, a nitrene or imene (R–N) is the nitrogen analogue of a carbene. The nitrogen atom is uncharged and univalent, so it has only 5 electrons in its valence level—one covalent bond and four non-bonded electrons. It is therefore considered an electrophile due to the unsatisfied octet. A nitrene is a reactive intermediate and is involved in many chemical reactions. The simplest nitrene, HN, is called imidogen, and that term is sometimes used as a synonym for the nitrene class.
In chemistry, a dehydration reaction is a conversion that involves the loss of water from the reacting molecule or ion. Dehydration reactions are common processes, the reverse of a hydration reaction. Common dehydrating agents used in organic synthesis include sulfuric acid and alumina. Often dehydration reactions are effected with heating.
An allylic rearrangement or allylic shift is an organic reaction in which the double bond in an allyl chemical compound shifts to the next carbon atom. It is encountered in nucleophilic substitution.
The Wittig reaction or Wittig olefination is a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide to give an alkene and triphenylphosphine oxide.
1,3,5,7-Cyclooctatetraene (COT) is an unsaturated derivative of cyclooctane, with the formula C8H8. It is also known as [8]annulene. This polyunsaturated hydrocarbon is a colorless to light yellow flammable liquid at room temperature. Because of its stoichiometric relationship to benzene, COT has been the subject of much research and some controversy.
Azomethine ylides are nitrogen-based 1,3-dipoles, consisting of an iminium ion next to a carbanion. They are used in 1,3-dipolar cycloaddition reactions to form 5-membered heterocycles, including pyrrolidines and pyrrolines. These reactions are highly stereo- and regioselective, and have the potential to form four new contiguous stereocenters. Azomethine ylides thus have high utility in total synthesis, and formation of chiral ligands and pharmaceuticals. Azomethine ylides can be generated from many sources, including aziridines, imines, and iminiums. They are often generated in situ, and immediately reacted with dipolarophiles.
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.
Aziridines are organic compounds containing the aziridine functional group, a three-membered heterocycle with one amine (-NR-) and two methylene bridges. The parent compound is aziridine, with molecular formula C
2H
4NH.
The Combes quinoline synthesis is a chemical reaction, which was first reported by Combes in 1888. It involves the condensation of unsubstituted anilines (1) with β-diketones (2) to form substituted quinolines (4) after an acid-catalyzed ring closure of an intermediate Schiff base (3). Further studies and reviews of the Combes quinoline synthesis and its variations have been published by Alyamkina et al., Bergstrom and Franklin, Born, and Johnson and Mathews.
The Willgerodt rearrangement or Willgerodt reaction is an organic reaction converting an aryl alkyl ketone to the corresponding amide by reaction with ammonium polysulfide, named after Conrad Willgerodt. The formation of the corresponding carboxylic acid is a side reaction. When the alkyl group is an aliphatic chain, multiple reactions take place with the amide group always ending up at the terminal end.
Oseltamivir total synthesis concerns the total synthesis of the antiinfluenza drug oseltamivir marketed by Hoffmann-La Roche under the trade name Tamiflu. Its commercial production starts from the biomolecule shikimic acid harvested from Chinese star anise with a limited worldwide supply. Due to its limited supply, searches for alternative synthetic routes preferably not requiring shikimic acid are underway and to date several such routes have been published. Control of stereochemistry is important: the molecule has three stereocenters and the sought-after isomer is only 1 of 8 stereoisomers.
N-Hydroxysuccinimide (NHS) is an organic compound with the formula (CH2CO)2NOH. It is a white solid that is used as a reagent for preparing active esters in peptide synthesis.
The Fukuyama indole synthesis is a versatile tin mediated chemical reaction that results in the formation of 2,3-disubstituted indoles. A practical one-pot reaction that can be useful for the creation of disubstituted indoles. Most commonly tributyltin hydride is utilized as the reducing agent, with azobisisobutyronitrile (AIBN) as a radical initiator. Triethylborane can also be used as a radical initiator. The reaction can begin with either an ortho-isocyanostyrene or a 2-alkenylthioanilide derivative, both forming the indole through Radical cyclization via an α-stannoimidoyl radical. The R group can be a range of both basic and acidic sensitive functional groups such as esters, THP ethers, and β-lactams. In addition the reaction is not stereospecific, in that both the cis and trans isoform can be used to obtain the desired product.
The Hofmann–Löffler reaction (also referred to as Hofmann–Löffler–Freytag reaction, Löffler–Freytag reaction, Löffler–Hofmann reaction, as well as Löffler's method) is an organic reaction in which a cyclic amine 2 (pyrrolidine or, in some cases, piperidine) is generated by thermal or photochemical decomposition of N-halogenated amine 1 in the presence of a strong acid (concentrated sulfuric acid or concentrated CF3CO2H). The Hofmann–Löffler–Freytag reaction proceeds via an intramolecular hydrogen atom transfer to a nitrogen-centered radical and is an example of a remote intramolecular free radical C–H functionalization.
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.:
Olympicene is an organic carbon based molecule formed of five rings, of which four are benzene rings, joined in the shape of the Olympic rings.
Hydroxylamine-O-sulfonic acid ("HOSA") is the inorganic compound with molecular formula H3NO4S that is formed by the sulfonation of hydroxylamine with oleum. It is a white, water-soluble and hygroscopic, solid, commonly represented by the condensed structural formula H2NOSO3H, though it actually exists as a zwitterion and thus is more accurately represented as +H3NOSO3−. It is used as a reagent for the introduction of amine groups (–NH2), for the conversion of aldehydes into nitriles and alicyclic ketones into lactams (cyclic amides), and for the synthesis of variety of nitrogen-containing heterocycles.
Tetraethoxymethane is a chemical compound which is formally formed by complete ethylation of the hypothetical orthocarbonic acid C(OH)4 (orthocarboxylic acid violates the Erlenmeyer rule and is unstable in free state).
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