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Heterocyclic Chemistry
A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and applications of these heterocycles. Examples of heterocyclic compounds include all of the nucleic acids, the majority of drugs, most biomass (cellulose and related materials), and many natural and synthetic dyes. More than half of known compounds are heterocycles. 59% of US FDA-approved drugs contain nitrogen heterocycles. Classification The study of heterocyclic chemistry focuses especially on unsaturated derivatives, and the preponderance of work and applications involves unstrained 5- and 6-membered rings. Included are pyridine, thiophene, pyrrole, and furan. Another large class of heterocycles refers to those fused to benzene rings. For example, the fused benzene derivatives of pyridine, thiophene, pyrrole, and furan are quinol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heterocycle Compounds
A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and applications of these heterocycles. Examples of heterocyclic compounds include all of the nucleic acids, the majority of drugs, most biomass (cellulose and related materials), and many natural and synthetic dyes. More than half of known compounds are heterocycles. 59% of US FDA-approved drugs contain nitrogen heterocycles. Classification The study of heterocyclic chemistry focuses especially on unsaturated derivatives, and the preponderance of work and applications involves unstrained 5- and 6-membered rings. Included are pyridine, thiophene, pyrrole, and furan. Another large class of heterocycles refers to those fused to benzene rings. For example, the fused benzene derivatives of pyridine, thiophene, pyrrole, and furan are quinol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Azirine
Azirines are three-membered heterocyclic unsaturated (i.e. they contain a double bond) compounds containing a nitrogen atom and related to the saturated analogue aziridine. They are highly reactive yet have been reported in a few natural products such as Dysidazirine. There are two isomers of azirine: 1''H''-Azirines with a carbon-carbon double bond are not stable and rearrange to the tautomeric 2''H''-azirine, a compound with a carbon-nitrogen double bond. 2''H''-Azirines can be considered strained imines and are isolable. Preparation 2''H''-Azirine is most often obtained by the thermolysis of vinyl azides. During this reaction, a nitrene is formed as an intermediate. Alternatively, they can be obtained by oxidation of the corresponding aziridine. Azirine can be generated during photolysis of isoxazole. Due to the weak N-O bond, the isoxazole ring tends to collapse under UV irradiation, rearranging to azirine. : Reactions Photolysis of azirines (under 300 nm) is a very e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dioxirane
In chemistry, dioxirane is a compound with formula , whose molecule consists of a ring with one carbon and two oxygen atoms, and two hydrogen atoms attached to the carbon. It is a heterocyclic compound, the smallest cyclic organic peroxide. The compound itself is highly unstable and has never been observed at room temperature. Derivatives in which the hydrogens are replaced by other functional groups are called dioxiranes, and may be more stable. Some of them, such as dimethyldioxirane (DMDO) and the more reactive methyl(trifluoromethyl)dioxirane, are used in organic synthesis as oxidizing reagents, most notably as the key catalytic intermediate in the Shi epoxidation reaction. Difluorodioxirane, which boils at about –80 to –90 °C, is one of the very few dioxirane derivatives that is stable in pure form at room temperature. Synthesis Dioxirane is highly unstable and the majority of studies of it have been computational; it has been detected during the low tempera ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxaziridine
An oxaziridine is an organic molecule that features a three-membered heterocycle containing oxygen, nitrogen, and carbon. In their largest application, oxaziridines are intermediates in the industrial production of hydrazine. Oxaziridine derivatives are also used as specialized reagents in organic chemistry for a variety of oxidations, including alpha hydroxylation of enolates, epoxidation and aziridination of olefins, and other heteroatom transfer reactions. Oxaziridines also serve as precursors to amides and participate in +2cycloadditions with various heterocumulenes to form substituted five-membered heterocycles. Chiral oxaziridine derivatives effect asymmetric oxygen transfer to prochiral enolates as well as other substrates. Some oxaziridines also have the property of a high barrier to inversion of the nitrogen, allowing for the possibility of chirality at the nitrogen center. History Oxaziridine derivatives were first reported in the mid-1950s by Emmons and subsequ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diazirine
Diazirines are a class of organic molecules consisting of a carbon bound to two nitrogen atoms, which are double-bonded to each other, forming a cyclopropene-like ring, 3''H''-diazirene. They are isomeric with diazocarbon groups, and like them can serve as precursors for carbenes by loss of a molecule of dinitrogen. For example, irradiation of diazirines with ultraviolet light leads to carbene insertion into various C-H, N-H, and O-H bonds. Hence, diazirines have grown in popularity as small photo-reactive crosslinking reagents. They are often used in photoaffinity labeling studies to observe a variety of interactions, including ligand-receptor, ligand-enzyme, protein-protein, and protein-nucleic acid interactions. Synthesis A number of methods exist in the literature for the preparation of diazirines, which begin from a variety of reagents. Synthesis from ketones Generally, synthetic schemes that begin with ketones involve conversion of the ketone with the desired substituen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diaziridine
Diaziridines are heterocyclic compounds containing two nitrogen atoms in a three-membered ring. They can be considered as strained hydrazines. Unlike most amine types of structures, the nitrogen atoms of diaziridines are configurationally stable because the ring strain prevents Walden inversion. As a result, there can be various stereoisomeric forms of this structure. They are usually synthesized by treating a carbonyl compound with an aminating reagent like hydroxylamine-''O''-sulfonic acid and either ammonia or a primary aliphatic amine under slightly basic conditions.Synthesis of monocyclic diaziridines and their fused derivatives; N. N. Makhova, V. Y. Petukhova, V. V. Kuznetsov, ''Arkivoc'', 2008(i), 128-15 The final step is based on the intramolecular cyclization of an aminal. Reactions * Unsubstituted diaziridines are often directly oxidized (I2/NEt3) to the more stable diazirines. * They can undergo ring expansion reaction with electrophilic reagents like ketenes or isoc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thiirene
Thiirene is an organosulfur compound with the formula C2H2S. It can be viewed as a derivative of cyclopropene, but with the methylene group replaced by sulfur. It is antiaromatic and very labile. Thiirenes and derivatives No thiirene has been isolated at room temperature, but they have been observed spectroscopically at low temperatures. Thiirene-''S''-oxides and ''S''-alkylthiirinium salts have been characterized by X-ray crystallography X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles .... References {{chemistry-stub Sulfur heterocycles Three-membered rings ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Episulfide
In organic chemistry, episulfides are a class of organic compounds that contain a saturated, heterocyclic ring consisting of two carbon atoms and one sulfur atom. It is the sulfur analogue of an epoxide or aziridine. They are also known as thiiranes, olefin sulfides, thioalkylene oxides, and thiacyclopropanes. Episulfides are less common and generally less stable than epoxides. The most common derivative is ethylene sulfide (). Structure According to electron diffraction, the and distances in ethylene sulfide are respectively 1.473 and 1.811 Å. The and angles are respectively 66.0 and 48.0°. Preparation History A number of chemists in the early 1900s, including Staudinger and Pfenninger (1916), as well as Delepine (1920) studied episulfides.Sander, M. Thiiranes. Chem. Rev. 1966, 66(3), 297-339. I 1934 Dachlauer and Jackel devised a general synthesis of episulfides from epoxides using alkali thiocyanates and thiourea. Contemporary methods Following the lead of Dach ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thiirane
Thiirane, more commonly known as ethylene sulfide, is the cyclic chemical compound with the formula C2H4S. It is the smallest sulfur-containing heterocycle and the simplest episulfide. Like many organosulfur compounds, this species has a highly unpleasant odour. Thiirane is also used to describe any derivative of the parent ethylene sulfide. Structure According to electron diffraction, the C-C and C-S distances in ethylene sulfide are respectively 1.473 and 1.811 Å. The C-C-S and C-S-C angles are respectively 66.0 and 48.0°. Preparation and reactions It can be prepared by the reaction of ethylene carbonate and KSCN. For this purpose the KSCN is first melted under vacuum to remove water. :KSCN + C2H4O2CO → KOCN + C2H4S + CO2 Ethylenesulfide adds to amines to afford 2-mercaptoethylamines, which are good chelating ligands. :C2H4S + R2NH → R2NCH2CH2SH This process is often called mercaptoethylation. Oxidation of thiirane with periodate gives ethylene episulfoxi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphirene
Phosphirene is the hypothetical organophosphorus compound with the formula C2H2PH. As the simplest cyclic, unsaturated organophosphorus compound, phosphirene is the prototype of a family of related compounds that have attracted attention from researchers. Phosphirenes, that is substituted phosphirene compounds where one or more of the H's are replaced by organic substituents, are far more commonly discussed than the parent phosphirene. The first example of a phosphirene, 1,2,3-triphenylphosphirene was prepared via trapping of the phosphinidine complex Mo(CO)5PPh with diphenylacetylene Diphenylacetylene is the chemical compound C6H5C≡CC6H5. The molecule consists of two phenyl groups attached to a C2 unit. A colorless solid, it is used as a building block in organic synthesis and as a ligand in organometallic chemistry. Prep .... Placement of the double bond between the carbon atoms provides a 1Hphosphirene in which the phosphorus center is bonded to two carbon atoms and a hy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphirane
Phosphirane is the organophosphorus compound with the formula C2H4PH. It is a colorless gas of no commercial value. As the simplest cyclic, saturated organophosphorus compound, phosphirane is the prototype of a family of related compounds that have attracted attention from the research community. Phosphirane was first prepared by reaction of 1,2-dichloroethane with the conjugate base of phosphine Phosphine (IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula , classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting .... Phosphiranes, that is substituted phosphirene compounds where one or more of the H's are replaced organic substituents, are far more commonly discussed than the parent phosphirane. References * {{ cite book , title = A Guide to Organophosphorus Chemistry , author = Quin, L. D. , publisher = Wiley-Interscience , year = 2000 , isbn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxirene
Oxirene is a hypothesized heterocyclic chemical compound which contains an unsaturated three-membered ring containing two carbon atoms and one oxygen atom. Because it has never been observed, the substance is mainly studied by quantum chemical computational techniques. As the configuration is extremely strained and proposed to be an anti-aromatic 4 π electron system, oxirene is expected to be very high energy and unstable according to these calculations. Moreover, different computational methods draw different conclusions as to whether the structure constitutes a true molecule (i.e., a local minimum on the potential energy surface) or merely a transition state between two isomeric molecular species. Experimental indications exist that substituted oxirenes (as intermediates or transition states) may be involved in carbonylcarbene rearrangements observed in the Wolff rearrangement The Wolff rearrangement is a reaction in organic chemistry in which an α-diazocarbonyl compound ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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