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In organic chemistry, alkenols (shortened to enols) are a type of reactive structure or intermediate in organic chemistry that is represented as an alkene (olefin) with a hydroxyl group attached to one end of the alkene double bond (). The terms enol and alkenol are portmanteaus deriving from "-ene"/"alkene" and the "-ol" suffix indicating the hydroxyl group of alcohols, dropping the terminal "-e" of the first term. Generation of enols often involves deprotonation at the α position to the carbonyl group—i.e., removal of the hydrogen atom there as a proton . When this proton is not returned at the end of the stepwise process, the result is an anion termed an enolate (see images at right). The enolate structures shown are schematic; a more modern representation considers the molecular orbitals that are formed and occupied by electrons in the enolate. Similarly, generation of the enol often is accompanied by "trapping" or masking of the hydroxy group as an ether, such as a silyl enol ether. In organic chemistry, keto–enol tautomerism refers to a chemical equilibrium between a "keto" form (a carbonyl, named for the common ketone case) and an enol. The interconversion of the two forms involves the transfer of an alpha hydrogen atom and the reorganisation of bonding electrons. The keto and enol forms are tautomers of each other. Organic esters, ketones, and aldehydes with an α-hydrogen ( bond adjacent to the carbonyl group) often form enols. The reaction involves migration of a proton from carbon to oxygen: RC(O)CHR'_2

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Enol

Ketene

In organic chemistry, a ketene is an organic compound of the form , where R and R' are two arbitrary monovalent chemical groups (or two separate substitution sites in the same molecule). The name may also refer to the specific compound ethenone , the simplest ketene. Although they are highly useful, most ketenes are unstable. When used as reagents in a chemical procedure, they are typically generated when needed, and consumed as soon as (or while) they are produced. Ketenes were first studied as a class by Hermann Staudinger before 1905.

Isomer

In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism refers to the existence or possibility of isomers. Isomers do not necessarily share similar chemical or physical properties. Two main forms of isomerism are structural or constitutional isomerism, in which bonds between the atoms differ; and stereoisomerism or spatial isomerism, in which the bonds are the same but the relative positions of the atoms differ.

CH-233: Organic functions and reactions I

Le cours se focalisera sur les composés carbonyles: leur structures, réactivités, et leurs transformations; la réactivité des énols/énolates et leurs réactions fondamentales. L'importance de la compré

CH-435: Asymmetric catalysis for fine chemicals synthesis

The asymmetric synthesis of fine chemicals is a research topic of growing importance for the synthesis of modern materials, drugs and agrochemicals. In this lecture, the concepts of asymmetric catalys

CH-335: Asymmetric synthesis and retrosynthesis

La première partie du cours décrit les méthodes classiques de synthèse asymétrique. La seconde partie du cours traite des stratégies de rétrosynthèse basées sur l'approche par disconnection.

Catalytic Asymmetric Reactions in Organic Chemistry CH-435: Asymmetric catalysis for fine chemicals synthesis

Covers catalytic asymmetric reactions in organic chemistry, focusing on various methods and mechanisms.

Catalytic Asymmetric Reactions in Organic Chemistry

Explores catalytic asymmetric reactions in organic chemistry, focusing on electrophilic allylation, C-C bond activation, and chiral enolate generation.

Claisen Condensation: Mechanism and Applications CH-233: Organic functions and reactions I

Covers the Claisen condensation reaction and enamine chemistry, including enantioselective reactions using L-Proline as a catalyst.

Construction of Functional Superhydrophobic Biochars as Hydrogen Transfer Catalysts for Dehydrogenation of N-Heterocycles

Zhaowen Dong, Feng Zhou, Yujing Zhang

To endow metal-free materials with the high catalytic activity that is typically featured by a metal-based catalyst is yet a constant pursuit in the field of catalytic chemistry. In this work, novel functional biochars (DCNs) were prepared from wheat straw for the first time via a simple strategy of reconstructing the catalytic active sites in carbon precursors and subsequent controlled carbonization, which may be further applied in the oxidative dehydrogenation of N-heterocycles with ambient air as the oxidant. Whereas the superhydrophobicity of DCN-850 can effectively remove the only byproduct water to effectively reduce the possible effects of water on the catalyst, it also can decrease mass transfer resistance on active sites, thereby ensuring the reaction with high efficiencies and good generality. Especially, after several reuses, the activity and structures of DCN-850 remained unchanged in the catalytic system with water as a solvent. Furthermore, various characterization technologies and the model reaction were used to investigate the architectural attributes of DCNs, and the results show that there is a positive correlation between the catalytic performance and hydrophobicity of DCNs, as well as reveal that the catalytic active sites may be made up of a five-membered-ring ketone or its enol form and possibly a phenolic unit, which could be encapsulated in internal structures of catalysts and promote the reaction via the recycling of -C-C-OH and -C-C=O groups by the pathway of catalytic hydrogen transfer.

AMER CHEMICAL SOC2021

Rh(III)-Catalyzed C-H Functionalizations as Strategies for Versatile Organic Building Blocks

Van Manh Pham

Transition-metal catalyzed C-H functionalizations have impacted and changed synthetic approaches towards the construction of relevant complex molecules, comprising natural products, active pharmaceutical ingredients, and organic materials. This thesis describes the development of Rh(III)-catalyzed reactions via directed C-H functionalization and non-directed C-H functionalization. In this respect, acylated sulfonamides and N-sulfonyl ketimines were successfully employed as suitable directing groups, enabling directed C-H bond activation in the presence of a rhodium(III) catalyst. Subsequent migratory insertion of internal alkynes delivered a rich array of versatile benzosultams and chiral spirocyclic sultams, both of which are relevant structures in medicinal chemistry. Notably, the use of rhodium(III) complexes equipped with a suitable atropchiral cyclopentadienyl ligand enables enantioselective and high yielding access to the challenging spirocyclic sultam scaffolds. Complementary to the directed C-H bond functionalizations, application of CpRh(III) complexes in non-directed C-H functionalization reactions have been disclosed. Specific applications of this challenging strategy include the synthesis of highly valuable polyarenes from completely unbiased arenes via double C-H activation, and subsequent addition of internal alkynes. This method provides a convenient handle to access highly substituted and highly soluble acenes, possessing valuable electronic and photo physical properties. Furthermore, non-directed C-H functionalization of electron-rich heterocycles was also developed. In this context, a CpRh(III) catalyst enables a C2-selective activation of heteroarenes. Upon addition across an alkyne, a transmetalation to Cu(II) allows reductive C-O bond formation to deliver tetrasubstituted enol esters in a trans-selective fashion. A three-component coupling of heteroarenes, alkynes, and carboxylic acids was successfully demonstrated.

EPFL2016