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Ugi Reaction
The Ugi reaction is a multi-component reaction in organic chemistry involving a ketone or aldehyde, an amine, an isocyanide and a carboxylic acid to form a bis-amide. The reaction is named after Ivar Karl Ugi, who first reported this reaction in 1959. The Ugi reaction is exothermic and usually complete within minutes of adding the isocyanide. High concentration (0.5M - 2.0M) of reactants give the highest yields. Polar, aprotic solvents, like DMF, work well. However, methanol and ethanol have also been used successfully. This uncatalyzed reaction has an inherent high atom economy as only a molecule of water is lost, and the chemical yield in general is high. Several reviews have been published. Due to the reaction products being potential protein mimetics there have been many attempts to development an enantioselective Ugi reaction, the first successful report of which was in 2018. Reaction mechanism One plausible reaction mechanism is depicted below: Amine 1 and ketone ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ivar Karl Ugi
Ivar Karl Ugi (9 September 1930 in Saaremaa, Estonia – 29 September 2005 in Munich) was an Estonian-born German chemist who made major contributions to organic chemistry. He is known for the research on multicomponent reactions, yielding the Ugi reaction. Biography After he went to Germany from Estonia in 1941 he began his studies of chemistry in 1949 at the University of Tübingen until 1951. He became Dr. rer. nat. in 1954 at the Ludwig Maximilian University of Munich. He did his habilitation 1960 at the same university. After a short but very successful career in industry at Bayer from 1962 until 1968 when he joined the University of Southern California at Los Angeles. From 1971 he worked at the Technical University of Munich, and was an emeritus from 1999 until his death in 2005. Research and development The one pot reaction of a ketone or aldehyde, an amine, an isocyanide and a carboxylic acid to form a bis-amide is generally known as Ugi reaction The Ugi reaction is a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atom Economy
Atom economy (atom efficiency/percentage) is the conversion efficiency of a chemical process in terms of all atoms involved and the desired products produced. The simplest definition was introduced by Barry Trost in 1991 and is equal to the ratio between the mass of desired product to the total mass of products, expressed as a percentage. The concept of atom economy (AE) and the idea of making it a primary criterion for improvement in chemistry, is a part of the green chemistry movement that was championed by Paul Anastas from the early 1990s. Atom economy is an important concept of green chemistry philosophy, and one of the most widely used metrics for measuring the "greenness" of a process or synthesis. Good atom economy means most of the atoms of the reactants are incorporated in the desired products and only small amounts of unwanted byproducts are formed, reducing the economic and environmental impact of waste disposal. Atom economy can be written as: :\text = \frac \tim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reversible Reaction
A reversible reaction is a reaction in which the conversion of reactants to products and the conversion of products to reactants occur simultaneously. : \mathit aA + \mathit bB \mathit cC + \mathit dD A and B can react to form C and D or, in the reverse reaction, C and D can react to form A and B. This is distinct from a reversible process in thermodynamics. Weak acids and bases undergo reversible reactions. For example, carbonic acid: : H2CO3 (l) + H2O(l) ⇌ HCO3−(aq) + H3O+(aq). The concentrations of reactants and products in an equilibrium mixture are determined by the analytical concentrations of the reagents (A and B or C and D) and the equilibrium constant, ''K''. The magnitude of the equilibrium constant depends on the Gibbs free energy change for the reaction. So, when the free energy change is large (more than about 30 kJ mol−1), the equilibrium constant is large (log K > 3) and the concentrations of the reactants at equilibrium are very small. Such a reac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mumm Rearrangement
The Mumm rearrangement is an organic reaction and a rearrangement reaction. It describes a 1,3(O-N) acyl transfer of an acyl imidate or isoimide group to an imide. The reaction is of relevance as part of the Ugi reaction The Ugi reaction is a multi-component reaction in organic chemistry involving a ketone or aldehyde, an amine, an isocyanide and a carboxylic acid to form a bis-amide. The reaction is named after Ivar Karl Ugi, who first reported this reaction in 1 .... References {{Reflist, 30em Rearrangement reactions Name reactions Carboximidates ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrilium
A nitrilium ion is a nitrile that has been protonated, CNHsup>+, or alkylated, CNR′sup>+. Synthesis Nitriles are only weakly basic and are poor nucleophiles, but they will attack very reactive electrophiles such as carbocations. Nitrilium salts can be prepared by reacting nitriles with trialkyloxonium salts. The nitrilium ions thus formed can then be reduced to secondary amines with sodium borohydride in diglyme. This is a convenient route to secondary amines of the form RCH2—NH—R′. As intermediates Nitrilium ions are believed to be intermediates in the hydrolysis of nitriles, the Beckmann rearrangement, the Friedel-Crafts cyclization of amines to isoquinolines, the Schmidt reaction with ketones, and the Ugi, Ritter, Pinner Pinner is a London suburb in the London borough of Harrow, Greater London, England, northwest of Charing Cross, close to the border with Hillingdon, historically in the county of Middlesex. The population was 31,130 in 2011. Originally a m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nucleophilic Addition
In organic chemistry, a nucleophilic addition reaction is an addition reaction where a chemical compound with an electrophilic double or triple bond reacts with a nucleophile, such that the double or triple bond is broken. Nucleophilic additions differ from electrophilic additions in that the former reactions involve the group to which atoms are added accepting electron pairs, whereas the latter reactions involve the group donating electron pairs. Addition to carbon–heteroatom double bonds Nucleophilic addition reactions of nucleophiles with electrophilic double or triple bond (π bonds) create a new carbon center with two additional single, or σ, bonds.March Jerry; (1985). Advanced Organic Chemistry reactions, mechanisms and structure (3rd ed.). New York: John Wiley & Sons, inc. Addition of a nucleophile to carbon–heteroatom double or triple bonds such as >C=O or -C≡N show great variety. These types of bonds are polar (have a large difference in electronegativity betwe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iminium
In organic chemistry, an iminium cation is a polyatomic ion with the general structure . They are common in synthetic chemistry and biology. Structure Iminium cations adopt alkene-like geometries. The central C=N unit is nearly coplanar with all four substituents. The C=N distances, which are near 129 picometers in length, are shorter than C-N single bonds. Cis/trans isomers are observed. Formation Iminium cations are obtained by protonation and alkylation of imines: :RN=CR'_2 + H+ -> NH=CR'_2 :RN=CR'_2 + R''+ -> R''N=CR'_2 They also are generated by the condensation of secondary amines with ketones or aldehydes: :O=CR'_2 + R2NH + H+ 2N=CR'_2 + H2O This rapid, reversible reaction is one step in "iminium catalysis". More exotic routes to iminium cations are known, e.g. from ring-opening reactions of pyridine. Occurrence Iminium derivatives are common in biology. Pyridoxal phosphate reacts with amino acids to give iminium derivatives. Many iminium salts are en ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkylimino-de-oxo-bisubstitution
In organic chemistry, alkylimino-de-oxo-bisubstitution is the organic reaction of carbonyl compounds with amines to imines. The reaction name is based on the IUPAC Nomenclature for Transformations. The reaction is acid catalyzed and the reaction type is nucleophilic addition of the amine to the carbonyl compound followed by transfer of a proton from nitrogen to oxygen to a stable hemiaminal or carbinolamine. With primary amines water is lost in an elimination reaction to an imine. With aryl amines especially stable Schiff bases are formed. Reaction mechanism The reaction steps are reversible reactions and the reaction is driven to completion by removal of water e.g. by azeotropic distillation, molecular sieves or titanium tetrachloride. Primary amines react through an unstable hemiaminal intermediate which then splits off water. : Secondary amines do not lose water easily because they do not have a proton available and instead they often react further to an aminal: : or whe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amine
In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group (these may respectively be called alkylamines and arylamines; amines in which both types of substituent are attached to one nitrogen atom may be called alkylarylamines). Important amines include amino acids, biogenic amines, trimethylamine, and aniline; Inorganic derivatives of ammonia are also called amines, such as monochloramine (). The substituent is called an amino group. Compounds with a nitrogen atom attached to a carbonyl group, thus having the structure , are called amides and have different chemical properties from amines. Classification of amines Amines can be classified according to the nature and number of substituents on nitrogen. Aliphatic amines contain only H and alkyl substituents. A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reaction Mechanism
In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical change occurs. A chemical mechanism is a theoretical conjecture that tries to describe in detail what takes place at each stage of an overall chemical reaction. The detailed steps of a reaction are not observable in most cases. The conjectured mechanism is chosen because it is thermodynamically feasible, and has experimental support in isolated intermediates (see next section) or other quantitative and qualitative characteristics of the reaction. It also describes each reactive intermediate, activated complex, and transition state, and which bonds are broken (and in what order), and which bonds are formed (and in what order). A complete mechanism must also explain the reason for the reactants and catalyst used, the stereochemistry observed in reactants and products, all products formed and the amount of each. The electron or arrow pushing method is often used in i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enantioselective Synthesis
Enantioselective synthesis, also called asymmetric synthesis, is a form of chemical synthesis. It is defined by IUPAC as "a chemical reaction (or reaction sequence) in which one or more new elements of chirality are formed in a substrate molecule and which produces the stereoisomeric (enantiomeric or diastereomeric) products in unequal amounts." Put more simply: it is the synthesis of a compound by a method that favors the formation of a specific enantiomer or diastereomer. Enantiomers are stereoisomers that have opposite configurations at every chiral center. Diastereomers are stereoisomers that differ at one or more chiral centers. Enantioselective synthesis is a key process in modern chemistry and is particularly important in the field of pharmaceuticals, as the different enantiomers or diastereomers of a molecule often have different biological activity. Overview Many of the building blocks of biological systems such as sugars and amino acids are produced exclusively as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
