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Seyferth–Gilbert Homologation
The Seyferth–Gilbert homologation is a chemical reaction of an aryl ketone 1 (or aldehyde) with dimethyl (diazomethyl)phosphonate 2 and potassium tert-butoxide to give substituted alkynes 3. Dimethyl (diazomethyl)phosphonate 2 is often called the Seyferth–Gilbert reagent. This reaction is called a ''Homologation reactions, homologation'' because the product has exactly one additional carbon more than the starting material. Reaction mechanism Deprotonation of the Seyferth–Gilbert reagent A gives an anion B, which reacts with the ketone to form the oxaphosphetane D. Elimination of dimethylphosphate E gives the vinyl group, vinyl diazo-intermediate Fa and Fb. The generation of nitrogen gas gives a vinyl group, vinyl carbene G, which via a 1,2-rearrangement, 1,2-migration forms the desired alkyne H. Bestmann modification The dimethyl (diazomethyl)phosphonate carbanion can be generated ''in situ'' from dimethyl-1-diazo-2-oxopropylphosphonate (also called the Ohira-Bestmann ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diazo
In organic chemistry, the diazo group is an organic moiety consisting of two linked nitrogen atoms at the terminal position. Overall charge-neutral organic compounds containing the diazo group bound to a carbon atom are called diazo compounds or diazoalkanes and are described by the general structural formula . The simplest example of a diazo compound is diazomethane, . Diazo compounds () should not be confused with azo compounds () or with diazonium compounds (). Structure The electronic structure of diazo compounds is characterized by π electron density delocalized over the α-carbon and two nitrogen atoms, along with an orthogonal π system with electron density delocalized over only the terminal nitrogen atoms. Because all octet rule-satisfying resonance forms of diazo compounds have formal charges, they are members of a class of compounds known as 1,3-dipoles. Some of the most stable diazo compounds are α-diazo-β-diketones and α-diazo-β-diesters, in which the e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dietmar Seyferth
Dietmar Seyferth (January 11, 1929 – June 6, 2020) was an emeritus professor of chemistry at the Massachusetts Institute of Technology. He published widely on topics in organometallic chemistry and was the founding editor of the journal ''Organometallics''. Biography Seyferth was born in 1929 in Chemnitz, Saxony, Germany, and received his college education at the University of Buffalo. His PhD thesis, which focused on main group chemistry was completed under the mentorship of Eugene G. Rochow at Harvard. Seyferth spent his entire academic career at , where he initially concentrated on organophosphorus, organosilicon, and organomercury chemistry. He also contributed to organocobalt chemistry and organoiron chemistry, e.g. the popularization of Fe2S2(CO)6. He died on Saturday, June 6, 2020, due to complications from COVID-19 during the COVID-19 pandemic in Massachusetts. Seyferth has been widely recognized, notably with the American Chemical Society Award in Organom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methanol
Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a light, Volatility (chemistry), volatile, colorless and flammable liquid with a distinctive alcoholic odor similar to that of ethanol (potable alcohol), but is more acutely toxic than the latter. Methanol acquired the name wood alcohol because it was once produced through destructive distillation of wood. Today, methanol is mainly produced industrially by hydrogenation of carbon monoxide. Methanol consists of a methyl group linked to a polar hydroxyl group. With more than 20 million tons produced annually, it is used as a Precursor (chemistry), precursor to other commodity chemicals, including formaldehyde, acetic acid, methyl tert-butyl ether, methyl ''tert''-butyl ether, methyl benzoate, anisole, peroxyacids, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wittig Reaction
The Wittig reaction or Wittig olefination is a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide called a Wittig reagent. Wittig reactions are most commonly used to convert aldehydes and ketones to alkenes. Most often, the Wittig reaction is used to introduce a methylene group using methylenetriphenylphosphorane (Ph3P=CH2). Using this reagent, even a sterically hindered ketone such as camphor can be converted to its methylene derivative. Reaction mechanism Mechanistic studies have focused on unstabilized ylides, because the intermediates can be followed by NMR spectroscopy. The existence and interconversion of the betaine (3a and 3b) is subject of ongoing research. For lithium-free Wittig reactions, studies support a concerted formation of the oxaphosphetane without intervention of a betaine. In particular, phosphonium ylides 1 react with carbonyl compounds 2 via a +2cycloaddition that is sometimes described as having π2s+π2a">sub>π2s+π2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horner–Wadsworth–Emmons Reaction
The Horner–Wadsworth–Emmons (HWE) reaction is a chemical reaction used in organic chemistry of stabilized phosphonate carbanions with aldehydes (or ketones) to produce predominantly E-alkenes. In 1958, Leopold Horner published a modified Wittig reaction using phosphonate-stabilized carbanions. William S. Wadsworth and William D. Emmons further defined the reaction. In contrast to phosphonium ylides used in the Wittig reaction, phosphonate-stabilized carbanions are more nucleophilic but less basic. Likewise, phosphonate-stabilized carbanions can be alkylated. Unlike phosphonium ylides, the dialkylphosphate salt byproduct is easily removed by aqueous extraction. Several reviews have been published. Reaction mechanism The Horner–Wadsworth–Emmons reaction begins with the deprotonation of the phosphonate to give the phosphonate carbanion 1. Nucleophilic addition of the carbanion onto the aldehyde 2 (or ketone) producing 3a or 3b is the rate-limiting step. If ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caesium Carbonate
Caesium carbonate or cesium carbonate is a chemical compound with the chemical formula . It is white crystalline solid. Caesium carbonate has a high solubility in polar solvents such as water, ethanol and DMF. Its solubility is higher in organic solvents compared to other carbonates like potassium carbonate and sodium carbonate, although it remains quite insoluble in other organic solvents such as toluene, ''p''-xylene, and chlorobenzene. This compound is used in organic synthesis as a base. It also appears to have applications in energy conversion. Preparation Caesium carbonate can be prepared by thermal decomposition of caesium oxalate. Upon heating, caesium oxalate is converted to caesium carbonate with emission of carbon monoxide. : It can also be synthesized by reacting caesium hydroxide with carbon dioxide. : Chemical reactions Caesium carbonate facilitates the ''N''-alkylation of compounds such as sulfonamides, amines, β-lactams, indoles, heterocyclic compou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Safe And Scalable Synthesis Of Alkynes From Aldehydes
A safe (also called a strongbox or coffer) is a secure lockable enclosure used for securing valuable objects against theft or fire. A safe is usually a hollow cuboid or cylinder, with one face being removable or hinged to form a door. The body and door may be cast from metal (such as steel) or formed out of plastic through blow molding. Bank teller safes typically are secured to the counter, have a slit opening for dropping valuables into the safe without opening it, and a time-delay combination lock to foil thieves. One significant distinction between types of safes is whether the safe is secured to a wall or structure or if it can be moved around. History The first known safe dates back to the 13th century BC and was found in the tomb of Pharaoh Ramesses II. It was made of wood and consisted of a locking system resembling the modern pin tumbler lock. In the 16th century, blacksmiths in southern Germany, Austria, and France first forged cash boxes in sheet iron. These she ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Functional Group
In organic chemistry, a functional group is any substituent or moiety (chemistry), moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the rest of the molecule's composition. This enables systematic prediction of chemical reactions and behavior of chemical compounds and the design of chemical synthesis. The Reactivity (chemistry), reactivity of a functional group can be modified by other functional groups nearby. Functional group interconversion can be used in retrosynthetic analysis to plan organic synthesis. A functional group is a group of atoms in a molecule with distinctive Chemical property, chemical properties, regardless of the other atoms in the molecule. The atoms in a functional group are linked to each other and to the rest of the molecule by covalent bonds. For repeating units of polymers, functional groups attach to their Chemical polarity, nonp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synthesis (journal)
''Synthesis'' is a scientific journal published from 1969 to the present day by Thieme. Its stated purpose is the "advancement of the science of synthetic chemistry". From August 2006, selected articles are offered free of charge. The impact factor of this journal is 2.867 (2018).Journal Citation Reports, 2018 References Chemistry journals English-language journals Thieme academic journals {{chem-journal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synlett
''Synlett'' is an international scientific journal for accounts and rapid communications of original contributions of fundamental research in synthetic organic chemistry. The impact factor of this journal is 2.419 (2017). ''Nature'' featured a brief piece by the editor-in-chief of the journal in 2017, Benjamin List Benjamin List (; born 11 January 1968) is a German chemist who is one of the directors of the Max Planck Institute for Coal Research and professor of organic chemistry at the University of Cologne. He co-developed organocatalysis, a method of acc ..., where he discussed the journal's experience with the non-traditional peer review system. References Chemistry journals Thieme academic journals Academic journals established in 1989 {{chem-journal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
