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Baker–Venkataraman Rearrangement
The Baker–Venkataraman rearrangement is the chemical reaction of 2-acetoxyacetophenones with base to form 1,3-diketones. This rearrangement reaction proceeds via enolate formation followed by acyl transfer. It is named after the scientists Wilson Baker and K. Venkataraman. The Baker–Venkataraman rearrangement is often used in the synthesis of chromones and flavones. ''(also in thCollective Volume (1963) 4: 478 (PDF).'' After the base-catalyzed rearrangement, treatment with acid generally affords the chromone or flavone core, though other milder methods have been reported. Mechanism A base abstracts the hydrogen atom alpha to the aromatic ketone, forming an enolate. Then, the enolate attacks the ester carbonyl to form a cyclic alkoxide. The cyclic intermediate is opened up to form a more stable phenolate, which is protonated during acidic work-up to give the desired product. To complete the construction of the chromone or flavone core, cyclodehydration is required. This ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Reaction
A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking of chemical bonds between atoms, with no change to the Atomic nucleus, nuclei (no change to the elements present), and can often be described by a chemical equation. Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive Chemical element, elements where both electronic and nuclear changes can occur. The substance (or substances) initially involved in a chemical reaction are called reagent, reactants or reagents. Chemical reactions are usually characterized by a chemical change, and they yield one or more Product (chemistry), products, which usually have properties different from the reactants. Reactions often consist of a sequence o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synthesis (journal)
''Synthesis'' is a scientific journal published from 1969 to the present day by Thieme Medical Publishers, 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 [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kostanecki Acylation
The Kostanecki acylation is a method used in organic synthesis to form chromones or coumarins by acylation of ''O''-hydroxyaryl ketones with aliphatic acid anhydrides, followed by cyclization. If benzoic anhydride (or benzoyl chloride) is used, a particular type of chromone called a flavone is obtained. Mechanism The mechanism consists of three well-differentiated reactions:Ellis, G. P. (1977) ''Chromenes, Chromanones, and Chromones from The Chemistry of Heterocyclic Compounds'', Weissberger, A. and Taylor, E. C., eds.; Wiley & Sons: New York, vol. 31, p. 495. # Phenol ''O''-acylation with formation of a tetrahedral intermediate # Intramolecular aldol condensation to cyclize and to form a hydroxydihydrochromone # Elimination of the hydroxyl group to form the chromone (or coumarin) Examples * Alvocidib (flavopiridol) * Dimefline *Flavoxate See also * Allan–Robinson reaction * Baker–Venkataraman rearrangement The Baker–Venkataraman rearrangement is the chemical reaction o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allan–Robinson Reaction
The Allan–Robinson reaction is the chemical reaction of o-hydroxyaryl ketones with aromatic anhydrides to form flavones (or isoflavones). If aliphatic anhydrides are used, coumarins can also be formed. (See Kostanecki acylation.) : Mechanism : The first step is an enolization which is a proton transfer created a hydroxide instead of a carbonyl and an alkene instead of an alkane. The second step is an acylation in which the newly formed bond from the enolization attacks an electrophilic carbon in the anhydride. The third step displays the carboxylate functionality leaving since it is the best leaving group. As a result, the resulting carboxylate attacks an alpha hydrogen to create the enol functionality again in step four. The fifth step shows the nucleophilic hydroxide attacking the carbonyl carbon to create a new six membered heterocyclic ring. The resulting structure undergoes a proton transfer in step 6 to achieve the final product. All six of these steps occur in the reac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Baker Venkataraman Cyclodehydration
A baker is a tradesperson who bakes and sometimes sells breads and other products made of flour by using an oven or other concentrated heat source. The place where a baker works is called a bakery. History Ancient history Since grains have been a staple food for millennia, the activity of baking is a very old one. Control of yeast, however, is relatively recent.Wayne Gisslen, ''Professional Baking'' (4th ed.: John Wiley & Sons, 2005), p. 4. By the fifth and sixth centuries BCE, the ancient Greeks used enclosed ovens heated by wood fires; communities usually baked bread in a large communal oven. Greeks baked dozens and possibly hundreds of types of bread; Athenaeus described seventy-two varieties. In ancient Rome several centuries later, the first mass production of breads occurred, and "the baking profession can be said to have started at that time." Ancient Roman bakers used honey and oil in their products, creating pastries rather than breads. In ancient Rome, bakers (L ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phenolate
Phenolates (also called phenoxides) are anions, salts, and esters of phenols. They may be formed by reaction of phenols with strong base. Properties Alkali metal phenolates, such as sodium phenolate hydrolyze in aqueous solution to form basic solutions. At pH = 10, phenol and phenolate are in approximately 1:1 proportions. Phenolate anions are enolates. As such, they react as nucleophiles at both oxygen and carbon positions. In general, reaction at oxygen occurs under kinetic control, whereas reaction at carbon occurs under thermodynamic control. Uses Alkyl aryl ethers can be synthesized through the Williamson ether synthesis by treating sodium phenolate with an alkyl halide: :C6H5ONa + CH3I → C6H5OCH3 + NaI :C6H5ONa + (CH3O)2SO2 → C6H5OCH3 + (CH3O)SO3Na Production of salicylic acid Salicylic acid is produced in the Kolbe–Schmitt reaction between carbon dioxide and sodium phenolate. : See also * Sodium phenolate Sodium phenoxide (sodium phenolate) is an organ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkoxide
In chemistry, an alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They are written as , where R is the organic substituent. Alkoxides are strong bases and, when R is not bulky, good nucleophiles and good ligands. Alkoxides, although generally not stable in protic solvents such as water, occur widely as intermediates in various reactions, including the Williamson ether synthesis. Transition metal alkoxides are widely used for coatings and as catalysts. Enolates are unsaturated alkoxides derived by deprotonation of a bond adjacent to a ketone or aldehyde. The nucleophilic center for simple alkoxides is located on the oxygen, whereas the nucleophilic site on enolates is delocalized onto both carbon and oxygen sites. Ynolates are also unsaturated alkoxides derived from acetylenic alcohols. Phenoxides are close relatives of the alkoxides, in which the alkyl group is replaced by a derivative of be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrahedron Letters
''Tetrahedron Letters'' is a weekly international journal for rapid publication of full original research papers in the field of organic chemistry. According to the ''Journal Citation Reports'', the journal has a 2020 impact factor of 2.415. Indexing ''Tetrahedron Letters'' is indexed in: References See also *''Tetrahedron In geometry, a tetrahedron (plural: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertex corners. The tetrahedron is the simplest of all the o ...'' *'' Tetrahedron: Asymmetry'' Chemistry journals Weekly journals Publications established in 1959 Elsevier academic journals {{chem-journal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Syntheses
''Organic Syntheses'' is a peer-reviewed scientific journal that was established in 1921. It publishes detailed and checked procedures for the synthesis of organic compounds. A unique feature of the review process is that all of the data and experiments reported in an article must be successfully repeated in the laboratory of a member of the editorial board as a check for reproducibility prior to publication. The journal is published by Organic Syntheses, Inc., a non-profit corporation. An annual print version is published by John Wiley & Sons on behalf of Organic Syntheses, Inc. History Prior to World War I, work on synthetic organic chemistry in the United States had been quite limited, and most of the reagents used in laboratories had to be imported from Europe. When export stoppages and trade embargoes cut off this source, Clarence Derick, a professor of chemistry at University of Illinois at Urbana-Champaign, began an effort to synthesize these needed chemicals in industr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ketone
In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bond C=O). The simplest ketone is acetone (where R and R' is methyl), with the formula . Many ketones are of great importance in biology and in industry. Examples include many sugars (ketoses), many steroids (e.g., testosterone), and the solvent acetone. Nomenclature and etymology The word ''ketone'' is derived from ''Aketon'', an old German word for ''acetone''. According to the rules of IUPAC nomenclature, ketone names are derived by changing the suffix ''-ane'' of the parent alkane to ''-anone''. Typically, the position of the carbonyl group is denoted by a number, but traditional nonsystematic names are still generally used for the most important ketones, for example acetone and benzophenone. These nonsystematic names are considere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flavone
Flavone is an organic compound with the formula . A white solid, flavone is a derivative of chromone with a phenyl (Ph) substituent adjacent to the ether group. The compound is of little direct practical importance, but susbstituted derivatives, the flavones and flavonoids are a large class of nutritionally important natural products. Flavone can be prepared in the laboratory by cyclization of 2-hydroxacetophenone. Isomeric with flavone is isoflavone, where the phenyl group is adjacent to the ketone In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo .... References {{Flavones ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
