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Vinylcyclopropane Rearrangement
The vinylcyclopropane rearrangement or vinylcyclopropane-cyclopentene rearrangement is a ring expansion reaction, converting a vinyl-substituted cyclopropane ring into a cyclopentene ring. Intense experimental as well as computational investigations have revealed that mechanistically, the vinylcyclopropane rearrangement can be thought of as either a diradical-mediated two-step and/or orbital-symmetry-controlled pericyclic process. The amount by which each of the two mechanisms is operative is highly dependent on the substrate. Due to its ability to form cyclopentene rings the vinylcyclopropane rearrangement has served several times as a key reaction in complex natural product synthesis. Origins and history In 1959, a young research chemist with Humble Oil and Refining (Esso, now Exxon) named Norman P. Neureiter was instructed to find new uses for the excess butadiene produced from one of the refinery processes. Discussions about carbene chemistry with one of the company's most ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ring Expansion Reaction
Ring expansion and ring contraction reactions in the course of organic synthesis refer to a set of reactions which can lead to the expansion or contraction of an existing Ring (chemistry), ring. This often makes it possible to access structures that would be difficult if not impossible to synthesise with single cyclization reactions. Ring expansions are valuable because they allow access to larger systems that are difficult to synthesize through a single cyclization due to the slow rate of formation. Ring contractions are useful for making smaller, more strained rings from larger rings. Expansions are classified by the mechanism of expansion and the atom(s) added; contractions are characterized simply by the reactive intermediate which performs the contraction. Description In the course of an organic synthesis, a chemist often needs to form a new or alter an existing ring. Ring expansion and ring contraction reactions are used to expand or contract an existing Ring (chemistry) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nikolay Demyanov
Nikolay Yakovlevich Demyanov (russian: Никола́й Я́ковлевич Демья́нов; , Tver – March 19, 1938, Moscow), also known as Demjanov and Demjanow, was a Russian organic chemist and a member of the USSR Academy of Sciences (1929). He is internationally known for the Demjanov rearrangement organic reaction Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, Mechanistic Organ ... and other discoveries. He was a recipient of the Lenin Prize in 1930. Bibliography * External links Academician Nikolay Yakovlevich Demyanov 1861 births 1938 deaths Chemists from the Russian Empire Soviet chemists 20th-century chemists Russian inventors People from Tver Corresponding Members of the Russian Academy of Sciences (1917–1925) Full Members of the USSR Academy of Sciences Imperial ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dithiane
A dithiane is a heterocyclic compound composed of a cyclohexane core structure wherein two methylene bridges (-- units) are replaced by sulfur centres. The three isomeric parent heterocycles are 1,2-dithiane, 1,3-dithiane and 1,4-dithiane. 1,3-Dithianes 1,3-Dithianes are protecting group of some carbonyl-containing compounds due to their inertness to many conditions. They form by treatment of the carbonyl compound with 1,3-propanedithiol under conditions that remove water from the system. The protecting group can be removed with mercuric reagents, a process that exploits the high affinity of Hg(II) for thiolates. 1,3-Dithianes are also employed in umpolung reactions, such as the Corey–Seebach reaction:T. W. Green, P. G. M. Wuts, "Protective Groups in Organic Synthesis" Wiley-Interscience, New York, 1999. . : Typically, in organic synthesis, ketones and aldehydes are protected as their dioxolane Dioxolane is a heterocyclic acetal with the chemical formula (CH2)2O2CH2. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Elias James Corey
Elias James Corey (born July 12, 1928) is an American organic chemistry, organic chemist. In 1990, he won the Nobel Prize in Chemistry "for his development of the theory and methodology of organic synthesis", specifically retrosynthetic analysis. Regarded by many as one of the greatest living chemists, he has developed numerous synthetic reagents, methodologies and total syntheses and has advanced the science of organic synthesis considerably. Biography E.J. Corey (the surname was anglicized from Levantine Arabic ''Khoury'', meaning ''priest'') was born to Lebanese Greek Orthodox Christians, Lebanese Greek Orthodox Christian immigrants Fatima (née Hasham) and Elias Corey in Methuen, Massachusetts, north of Boston. His mother changed his name from William to "Elias" to honor his father, who died eighteen months after Corey's birth. His widowed mother, brother, two sisters, aunt and uncle all lived together in a spacious house, struggling through the Great Depression. As a young b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mechanism 04 05
Mechanism may refer to: *Mechanism (engineering), rigid bodies connected by joints in order to accomplish a desired force and/or motion transmission *Mechanism (biology), explaining how a feature is created *Mechanism (philosophy), a theory that all natural phenomena can be explained by physical causes *Mechanism (sociology), a theory that all social phenomena can be explained by the existence of a deterministic mechanism * "The Mechanism", song by Disclosure * ''The Mechanism'' (TV series), a Netflix TV series See also *Machine *Machine (mechanical) *Linkage (mechanical) *Mechanism design, the art of designing rules of a game to achieve a specific outcome *Mechanism of action, the means by which a drug exerts its biological effects *Defence mechanism, unconscious mechanisms aimed at reducing anxiety *Reaction mechanism, the sequence of reactions by which overall chemical change occurs *Antikythera mechanism, an ancient Greek analog computer *Theory of operation A theory of op ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mechanism 03
Mechanism may refer to: *Mechanism (engineering), rigid bodies connected by joints in order to accomplish a desired force and/or motion transmission *Mechanism (biology), explaining how a feature is created *Mechanism (philosophy), a theory that all natural phenomena can be explained by physical causes *Mechanism (sociology), a theory that all social phenomena can be explained by the existence of a deterministic mechanism * "The Mechanism", song by Disclosure * ''The Mechanism'' (TV series), a Netflix TV series See also *Machine *Machine (mechanical) *Linkage (mechanical) *Mechanism design, the art of designing rules of a game to achieve a specific outcome *Mechanism of action, the means by which a drug exerts its biological effects *Defence mechanism, unconscious mechanisms aimed at reducing anxiety *Reaction mechanism, the sequence of reactions by which overall chemical change occurs *Antikythera mechanism, an ancient Greek analog computer *Theory of operation A theory of op ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1,5-hydride Shift
A sigmatropic reaction in organic chemistry is a pericyclic reaction wherein the net result is one σ-bond is changed to another σ-bond in an uncatalyzed intramolecular reaction. The name ''sigmatropic'' is the result of a compounding of the long-established sigma designation from single carbon–carbon bonds and the Greek word ''tropos'', meaning turn. In this type of rearrangement reaction, a substituent moves from one part of a π-bonded system to another part in an intramolecular reaction with simultaneous rearrangement of the π system. True sigmatropic reactions are usually uncatalyzed, although Lewis acid catalysis is possible. Sigmatropic reactions often have transition-metal catalysts that form intermediates in analogous reactions. The most well-known of the sigmatropic rearrangements are the ,3Cope rearrangement, Claisen rearrangement, Carroll rearrangement, and the Fischer indole synthesis. Overview of sigmatropic shifts Woodward–Hoffman sigmatropic shift nomenclatur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mechanism 02
Mechanism may refer to: *Mechanism (engineering), rigid bodies connected by joints in order to accomplish a desired force and/or motion transmission *Mechanism (biology), explaining how a feature is created *Mechanism (philosophy), a theory that all natural phenomena can be explained by physical causes *Mechanism (sociology), a theory that all social phenomena can be explained by the existence of a deterministic mechanism * "The Mechanism", song by Disclosure * ''The Mechanism'' (TV series), a Netflix TV series See also *Machine *Machine (mechanical) *Linkage (mechanical) *Mechanism design, the art of designing rules of a game to achieve a specific outcome *Mechanism of action, the means by which a drug exerts its biological effects *Defence mechanism, unconscious mechanisms aimed at reducing anxiety *Reaction mechanism, the sequence of reactions by which overall chemical change occurs *Antikythera mechanism, an ancient Greek analog computer *Theory of operation A theory of op ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mechanism 01
Mechanism may refer to: *Mechanism (engineering), rigid bodies connected by joints in order to accomplish a desired force and/or motion transmission *Mechanism (biology), explaining how a feature is created *Mechanism (philosophy), a theory that all natural phenomena can be explained by physical causes *Mechanism (sociology), a theory that all social phenomena can be explained by the existence of a deterministic mechanism * "The Mechanism", song by Disclosure * ''The Mechanism'' (TV series), a Netflix TV series See also *Machine *Machine (mechanical) *Linkage (mechanical) *Mechanism design, the art of designing rules of a game to achieve a specific outcome *Mechanism of action, the means by which a drug exerts its biological effects *Defence mechanism, unconscious mechanisms aimed at reducing anxiety *Reaction mechanism, the sequence of reactions by which overall chemical change occurs *Antikythera mechanism, an ancient Greek analog computer *Theory of operation A theory of op ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
