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Kröhnke Pyridine Synthesis
The Kröhnke pyridine synthesis is reaction in organic synthesis between α-pyridinium methyl ketone salts and α, β-unsaturated carbonyl compounds used to generate highly functionalized pyridines. Pyridines occur widely in natural and synthetic products, so there is wide interest in routes for their synthesis. The method is named after Fritz Kröhnke. Reaction development Discovery In his work at the University of Giessen, Kröhnke observed condensation of α-pyridinium methyl ketone salts 1 with α,β-unsaturated carbonyl compounds 2 via a Michael reaction when treated with ammonium acetate to give 2,4,6-trisubstituted pyridines in high yields under mild reaction conditions. The proposed intermediates, 1, 5-dicarbonyl compound 3, have not been isolated. Since its discovery, the Kröhnke synthesis has enjoyed broad applicability to the preparation of di-,tri- and tetrapyridine derivatives, demonstrating a number of advantages over related reactions such as the Hantzsch pyridine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one of the most important branches of organic chemistry. There are several main areas of research within the general area of organic synthesis: '' total synthesis'', '' semisynthesis'', and ''methodology''. Total synthesis A total synthesis is the complete chemical synthesis of complex organic molecules from simple, commercially available petrochemical or natural precursors. Total synthesis may be accomplished either via a linear or convergent approach. In a ''linear'' synthesis—often adequate for simple structures—several steps are performed one after another until the molecule is complete; the chemical compounds made in each step are called synthetic intermediates. Most often, each step in a synthesis refers to a separate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Michael Acceptor
In organic chemistry, the Michael reaction or Michael addition is a reaction between a Michael donor (an enolate or other nucleophile) and a Michael acceptor (usually an α,β-unsaturated carbonyl) to produce a Michael adduct by creating a carbon-carbon bond at the acceptor's β-carbon. It belongs to the larger class of conjugate additions and is widely used for the mild formation of carbon-carbon bonds. The Michael addition is an important atom-economical method for diastereoselective and enantioselective C–C bond formation, and many asymmetric variants exist : In this general Michael addition scheme, either or both of R and R' on the nucleophile (the Michael donor) represent electron-withdrawing substituents such as acyl, cyano, nitro, or sulfone groups, which make the adjacent methylene hydrogen acidic enough to form a carbanion when reacted with the base, ''B:''. For the alkene (the Michael acceptor), the R" substituent is usually a carbonyl, which makes th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homo-coupling
A coupling reaction in organic chemistry is a general term for a variety of reactions where two fragments are joined together with the aid of a metal catalyst. In one important reaction type, a main group organometallic compound of the type R-M (R = organic fragment, M = main group center) reacts with an organic halide of the type R'-X with formation of a new carbon-carbon bond in the product R-R'. The most common type of coupling reaction is the cross coupling reaction. Richard F. Heck, Ei-ichi Negishi, and Akira Suzuki were awarded the 2010 Nobel Prize in Chemistry for developing palladium-catalyzed cross coupling reactions. Broadly speaking, two types of coupling reactions are recognized: *Heterocouplings combine two different partners, such as in the Heck reaction of an alkene (RC=CH) and an alkyl halide (R'-X) to give a substituted alkene, or the Corey–House synthesis of an alkane by the reaction of a lithium diorganylcuprate (R2CuLi) with an organyl (pseudo)halide (R ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Terpyridine
Terpyridine (2,2';6',2"-terpyridine, often abbreviated to Terpy or Tpy) is a heterocyclic compound derived from pyridine. It is a white solid that is soluble in most organic solvents. The compound is mainly used as a ligand in coordination chemistry. Synthesis Terpyridine was first synthesized by G. Morgan and F. H. Burstall in 1932 by the oxidative coupling of pyridines. This method, however, proceeded in low yields. More efficient syntheses have since been described, mainly starting from 2-acetylpyridine. One method produces an enaminone by the reaction of 2-acetylpyridine with N,N-dimethylformamide dimethyl acetal. The base-catalyzed reaction of 2-acetylpyridine with carbon disulfide followed by alkylation with methyl iodide gives C5H4NCOCH=C(SMe)2. Condensation of this species with 2-acetylpyridine forms the related 1,5-diketone, which condenses with ammonium acetate to form a terpyridine. Treatment of this derivative with Raney nickel removes the thioether group. Ot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bipyridine
Bipyridines also known as bipyridyls, dipyridyls, and dipyridines, are a family of chemical compounds with the formula (C5H4N)2, consisting of two pyridyl (C5H4N) rings. Pyridine is an aromatic nitrogen-containing heterocycle. Bipyridines are of significance in pesticides. Six isomers of bipyridine exist, but two are prominent: 2,2′-bipyridine is a popular ligand. 4,4'-Bipyridine is a precursor to the commercial herbicide paraquat. The bipyridines are all colourless solids, which are soluble in organic solvents and slightly soluble in water. 2,2′-Bipyridine 2,2′-Bipyridine (2,2′-bipy) is a chelating ligand that forms complexes with most transition metal ions that are of broad academic interest. Many of these complexes have distinctive optical properties, and some are of interest for analysis. Its complexes are used in studies of electron and energy transfer, supramolecular and materials chemistry, and catalysis. 2,2′-Bipyridine is used in the manufacture of d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Furan
Furan is a heterocyclic organic compound, consisting of a five-membered aromatic ring with four carbon atoms and one oxygen atom. Chemical compounds containing such rings are also referred to as furans. Furan is a colorless, flammable, highly volatile liquid with a boiling point close to room temperature. It is soluble in common organic solvents, including alcohol, ether, and acetone, and is slightly soluble in water. Its odor is "strong, ethereal; chloroform-like". It is toxic and may be carcinogenic in humans. Furan is used as a starting point for other speciality chemicals. History The name "furan" comes from the Latin ''furfur'', which means bran. (Furfural is produced from bran.) The first furan derivative to be described was 2-furoic acid, by Carl Wilhelm Scheele in 1780. Another important derivative, furfural, was reported by Johann Wolfgang Döbereiner in 1831 and characterised nine years later by John Stenhouse. Furan itself was first prepared by Heinrich Limp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
