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Squaramide Catalysis
Within the area of organocatalysis, squaramide catalysis describes the use of squaramides to accelerate and stereochemically alter organic transformations. The effects arise through hydrogen-bonding interactions between the substrate and the squaramide, unlike classic catalysts, and is thus a type of Hydrogen-bond catalysis, hydrogen-bond catalyst. The scope of these small-molecule H-bond donors termed squaramide organocatalysis covers both non-stereoselective and stereoselective applications. Structure A squaramide organocatalyst typically contains the squaramide group and a Hydrogen bond, hydrogen bond donor which is usually a Amine, tertiary amine group. The 3,5-bis(trifluoromethyl)phenyl-group is commonly used for the R group. For Enantioselective synthesis, enantioselective squaramide catalysis, chirality is induced via the tertiary amine group. There are cases where both sides of the squaramide are tertiary amines. Catalyst-substrate interactions The interaction between t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organocatalysis
In organic chemistry, organocatalysis is a form of catalysis in which the rate of a chemical reaction is increased by an organic catalyst. This "organocatalyst" consists of carbon, hydrogen, sulfur and other nonmetal elements found in organic compounds.Special Issue: Because of their similarity in composition and description, they are often mistaken as a misnomer for enzymes due to their comparable effects on reaction rates and forms of catalysis involved. Organocatalysts which display secondary amine functionality can be described as performing either enamine catalysis (by forming catalytic quantities of an active enamine nucleophile) or iminium catalysis (by forming catalytic quantities of an activated iminium electrophile). This mechanism is typical for covalent organocatalysis. Covalent binding of substrate normally requires high catalyst loading (for proline-catalysis typically 20–30 mol%). Noncovalent interactions such as hydrogen-bonding facilitates low catalyst loa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitro Compound
In organic chemistry, nitro compounds are organic compounds that contain one or more nitro functional groups (). The nitro group is one of the most common explosophores (functional group that makes a compound explosive) used globally. The nitro group is also strongly electron-withdrawing. Because of this property, bonds alpha (adjacent) to the nitro group can be acidic. For similar reasons, the presence of nitro groups in aromatic compounds retards electrophilic aromatic substitution but facilitates nucleophilic aromatic substitution. Nitro groups are rarely found in nature. They are almost invariably produced by nitration reactions starting with nitric acid. Synthesis Preparation of aromatic nitro compounds Aromatic nitro compounds are typically synthesized by nitration. Nitration is achieved using a mixture of nitric acid and sulfuric acid, which produce the nitronium ion (), which is the electrophile: + The nitration product produced on the largest scale, by f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Squaramide
Squaramide is the organic compound with the formula O2C4(NH2)2. Not an amide in the usual sense, it is a derivative of squaric acid wherein the two OH groups are replaced by NH2 groups. Squaramides refer to a large class of derivatives wherein some of the H's are replaced by organic substituents. Exploiting their rigid planar structures, these compounds are of interest as hydrogen-bond donors in supramolecular chemistry and squaramide catalysis. Squaramides exhibit 10-50x greater affinity for halides than do thioureas. Squaramides also find application in medicinal chemistry, metabolomics and material science due to their ability to selectively conjugate amines Squaramide is prepared by ammonolysis In chemistry, ammonolysis (/am·mo·nol·y·sis/) is the process of splitting ammonia into NH2- + H+. Ammonolysis reactions can be conducted with organic compounds to produce amines (molecules containing a nitrogen atom with a lone pair, :N), o ... of diesters of squaric acid: :O ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thiourea Organocatalysis
Within the area of organocatalysis, (thio)urea organocatalysis describes the use of ureas and thioureas to accelerate and stereochemically alter organic transformations. The effects arise through hydrogen-bonding interactions between the substrate and the (thio)urea. Unlike classical catalysts, these organocatalysts interact by non-covalent interactions, especially hydrogen bonding ("partial protonation"). The scope of these small-molecule H-bond donors termed (thio)urea organocatalysis covers both non-stereoselective and stereoselective reactions. Catalyst-substrate interactions Hydrogen-bonding between thiourea derivatives and carbonyl substrates involve two hydrogen bonds provided by coplanar amino substituents in the (thio)urea. Squaramide catalysts engage in double H-bonding interactions and are often superior to thioureas. Thioureas are often found to be stronger hydrogen-bond donors (''i.e.,'' more acidic) than ureas because their amino groups are more positively charg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organocatalysis
In organic chemistry, organocatalysis is a form of catalysis in which the rate of a chemical reaction is increased by an organic catalyst. This "organocatalyst" consists of carbon, hydrogen, sulfur and other nonmetal elements found in organic compounds.Special Issue: Because of their similarity in composition and description, they are often mistaken as a misnomer for enzymes due to their comparable effects on reaction rates and forms of catalysis involved. Organocatalysts which display secondary amine functionality can be described as performing either enamine catalysis (by forming catalytic quantities of an active enamine nucleophile) or iminium catalysis (by forming catalytic quantities of an activated iminium electrophile). This mechanism is typical for covalent organocatalysis. Covalent binding of substrate normally requires high catalyst loading (for proline-catalysis typically 20–30 mol%). Noncovalent interactions such as hydrogen-bonding facilitates low catalyst loa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DMSO
Dimethyl sulfoxide (DMSO) is an organosulfur compound with the formula . This colorless liquid is the sulfoxide most widely used commercially. It is an important polar aprotic solvent that dissolves both polar and nonpolar compounds and is miscible in a wide range of organic solvents as well as water. It has a relatively high boiling point. DMSO is metabolised to compounds that leave a garlic-like taste in the mouth after DMSO is absorbed by skin. In terms of chemical structure, the molecule has idealized Cs symmetry. It has a trigonal pyramidal molecular geometry consistent with other three-coordinate S(IV) compounds, with a nonbonded electron pair on the approximately tetrahedral sulfur atom. Synthesis and production Dimethyl sulfoxide was first synthesized in 1866 by the Russian scientist Alexander Zaytsev, who reported his findings in 1867. Its modern use as an industrial solvent began through popularization by Thor Smedslund at the Stepan Chemical Company. Dimeth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dimethylformamide
Dimethylformamide, DMF is an organic compound with the chemical formula . Its structure is . Commonly abbreviated as DMF (although this initialism is sometimes used for 2,5-dimethylfuran, dimethylfuran, or dimethyl fumarate), this colourless liquid is Miscibility, miscible with Water (molecule), water and the majority of organic liquids. DMF is a common solvent for chemical reactions. Dimethylformamide is odorless, but chemical purity, technical-grade or degraded samples often have a fishy smell due to impurity of dimethylamine. Dimethylamine degradation impurities can be removed by Sparging (chemistry), sparging samples with an inert gas such as argon or by sonication, sonicating the samples under reduced pressure. As its name indicates, it is structurally related to formamide, having two methyl groups in the place of the two hydrogens. DMF is a polar molecule, polar (hydrophilic) aprotic solvent with a high boiling point. It facilitates reactions that follow polar mechanisms, such ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Achiral
Chirality () is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is distinguishable from its mirror image; that is, it cannot be superposed (not to be confused with superimposed) onto it. Conversely, a mirror image of an ''achiral'' object, such as a sphere, cannot be distinguished from the object. A chiral object and its mirror image are called ''enantiomorphs'' (Greek, "opposite forms") or, when referring to molecules, ''enantiomers''. A non-chiral object is called ''achiral'' (sometimes also ''amphichiral'') and can be superposed on its mirror image. The term was first used by Lord Kelvin in 1893 in the second Robert Boyle Lecture at the Oxford University Junior Scientific Club which was published in 1894: Human hands are perhaps the most recognized example of chirality. The left hand is a non-superposable mirror i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quinoline
Quinoline is a heterocyclic aromatic organic compound with the chemical formula C9H7N. It is a colorless hygroscopic liquid with a strong odor. Aged samples, especially if exposed to light, become yellow and later brown. Quinoline is only slightly soluble in cold water but dissolves readily in hot water and most organic solvents. Quinoline itself has few applications, but many of its derivatives are useful in diverse applications. A prominent example is quinine, an alkaloid found in plants. Over 200 biologically active quinoline and quinazoline alkaloids are identified. 4-Hydroxy-2-alkylquinolines (HAQs) are involved in antibiotic resistance. Occurrence and isolation Quinoline was first extracted from coal tar in 1834 by German chemist Friedlieb Ferdinand Runge; he called quinoline ''leukol'' ("white oil" in Greek). Coal tar remains the principal source of commercial quinoline. In 1842, French chemist Charles Gerhardt obtained a compound by dry distilling quinine, st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methoxy Group
In organic chemistry, a methoxy group is the functional group consisting of a methyl group bound to oxygen. This alkoxy group has the formula . On a benzene ring, the Hammett equation classifies a methoxy substituent at the ''para'' position as an electron-donating group, but as an electron-withdrawing group if at the ''meta'' position. At the ''ortho'' position, steric effects are likely to cause a significant alteration in the Hammett equation prediction, which otherwise follows the same trend as that of the ''para'' position. Occurrence The simplest of methoxy compounds are methanol and dimethyl ether. Other methoxy ethers include anisole and vanillin. Many metal alkoxides contain methoxy groups, such as tetramethyl orthosilicate and titanium methoxide. Esters with a methoxy group can be referred to as methyl esters, and the —COOCH3 substituent is called a methoxycarbonyl. Biosynthesis In nature, methoxy groups are found on nucleosides subjected to 2′-''O''-methy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methylene Group
A methylene group is any part of a molecule that consists of two hydrogen atoms bound to a carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ... atom, which is connected to the remainder of the molecule by two single bonds. The group may be represented as or , where the '>' denotes the two bonds. This stands in contrast to a situation where the carbon atom is bound to the rest of the molecule by a double bond, which is preferably called a methylidene group, represented . Formerly the methylene name was used for both isomers. The name “ methylene bridge“ can be used for the single-bonded isomer, to emphatically exclude methylidene. The distinction is often important, because the double bond is chemically different from two single bonds. The methylene group should be d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cascade Reaction
A cascade reaction, also known as a domino reaction or tandem reaction, is a chemical process that comprises at least two consecutive reactions such that each subsequent reaction occurs only in virtue of the chemical functionality formed in the previous step.Tietze, L. F.; Beifuss, U. ''Angew. Chem. Int. Ed.'' 1993, ''32'', 131–163. In cascade reactions, isolation of intermediates is not required, as each reaction composing the sequence occurs spontaneously. In the strictest definition of the term, the reaction conditions do not change among the consecutive steps of a cascade and no new reagents are added after the initial step.Padwa, A.; Bur, S. K. ''Tetrahedron'' 2007, ''63'', 5341–5378. By contrast, one-pot procedures similarly allow at least two reactions to be carried out consecutively without any isolation of intermediates, but do not preclude the addition of new reagents or the change of conditions after the first reaction. Thus, any cascade reaction is also a one-pot p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
