ChemInform Abstract: (2+2)CYCLOADDITIONS OF TETRACYANOETHYLENE TO ENOL ETHERS, STRUCTURE OF THE PRODUCT OF INTERCEPTION WITH ALCOHOL

Marine natural products (MNPs) containing pyrone rings have been isolated from numerous marine organisms, and also produced by marine fungi and bacteria, particularly, actinomycetes. They constitute a versatile structure unit of bioactive natural products that exhibit various biological activities such as antibiotic, antifungal, cytotoxic, neurotoxic, phytotoxic and anti-tyrosinase. The two structure isomers of pyrone ring are γ- pyrone and α-pyrone. In terms of chemical motif, γ-pyrone is the vinologous form of α- pyrone which possesses a lactone ring. Actinomycete bacteria are responsible for the production of several α-pyrone compounds such as elijopyrones A-D, salinipyrones and violapyrones etc. to name a few. A class of pyrone metabolites, polypropionates which have fascinating carbon skeleton, is primarily produced by marine molluscs. Interestingly, some of the pyrone polytketides which are found in cone snails are actually synthesized by actinomycete bacteria. Several pyrone derivatives have been obtained from marine fungi such as Aspergillums flavus, Altenaria sp., etc. The γ-pyrone derivative namely, kojic acid obtained from Aspergillus fungus has high commercial demand and finds various applications. Kojic acid and its derivative displayed inhibition of tyrosinase activity and, it is also extensively used as a ligand in coordination chemistry. Owing to their commercial and biological significance, the synthesis of pyrone containing compounds has been given attention over the past years. Few reviews on the total synthesis of pyrone containing natural products namely, polypropionate metabolites have been reported. However, these reviews skipped other marine pyrone metabolites and also omitted discussion on isolation and detailed biological activities. This review presents a brief account of the isolation of marine metabolites containing a pyrone ring and their reported bio-activities. Further, the review covers the synthesis of marine pyrone metabolites such as cyercene-A, placidenes, onchitriol-I, onchitriol-II, crispatene, photodeoxytrichidione, (-) membrenone-C, lihualide-B, macrocyclic enol ethers and auripyrones-A & B.

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Addition of Allylsilanes and Silyl Enol Ethers to Small Oxygenated Rings: New Tools for Organic Synthesis

Current Organic Chemistry ◽

10.2174/1385272819666140201002221 ◽

2014 ◽

Vol 18 (5) ◽

pp. 525-546 ◽

Cited By ~ 4

Author(s):

Carmen Hernandez-Cervantes ◽

Miriam Alvarez-Corral ◽

Manuel Munoz-Dorado ◽

Ignacio Rodriguez-Garcia

Keyword(s):

Organic Synthesis ◽

Enol Ethers ◽

Silyl Enol Ethers

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α-Alkoxyalkyl Triphenylphosphonium Salts: Synthesis and Reactions

Current Organic Chemistry ◽

10.2174/1385272823666190926092242 ◽

2019 ◽

Vol 23 (16) ◽

pp. 1738-1755

Author(s):

Humaira Y. Gondal ◽

Zain M. Cheema ◽

Abdul R. Raza ◽

Ahmed Abbaskhan ◽

M. I. Chaudhary

Keyword(s):

Carbonyl Compounds ◽

Claisen Rearrangement ◽

Alder Reaction ◽

Coupling Reactions ◽

Phosphonium Salts ◽

Organic Transformations ◽

Enol Ethers ◽

Wide Range ◽

Synthetic Methodologies ◽

Alkoxy Groups

Following numerous applications of Wittig reaction now functionalized phosphonium salts are gaining attention due to their characteristic properties and diverse reactivity. This review is focused on α-alkoxyalkyl triphenylphosphonium salts: an important class of functionalized phosphonium salts. Alkoxymethyltriphenylphosphonium salts are majorly employed in the carbon homologation of carbonyl compounds and preparation of enol ethers. Their methylene insertion strategy is extensively demonstrated in the total synthesis of a wide range of natural products and other important organic molecules. Similarly enol ethers prepared thereof are important precursors for different organic transformations like Diels-Alder reaction, Claisen rearrangement, Coupling reactions, Olefin metathesis and Nazarov cyclization. Reactivity of these α-alkoxyalkylphosphonium salts have also been studied in the nucleophilic substitution reactions. A distinctive application of this class of phosphonium salts was recently reported in the phenylation of carbonyl compounds under very mild conditions. Synthesis of structurally diverse alkoxymethyltriphenylphosphonium salts with variation in alkoxy groups as well as counter anions are reported in literature. Here we present a detailed account of different synthetic methodologies for the preparation of this unique class of quaternary phosphonium salts and their applications in organic synthesis.

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Bench‐Stable Electrophilic Fluorinating Reagents for Highly Selective Mono‐ and Difluorination of Silyl Enol Ethers

Chemistry - A European Journal ◽

10.1002/chem.202101499 ◽

2021 ◽

Author(s):

Kohsuke Aikawa ◽

KyoKo Nozaki ◽

Takashi Okazoe ◽

Yuichiro Ishibashi ◽

Akiya Adachi

Keyword(s):

Enol Ethers ◽

Silyl Enol Ethers

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Haloacetylated enol ethers: a way out for the regioselective synthesis of biologically active heterocycles

European Journal of Organic Chemistry ◽

10.1002/ejoc.202100495 ◽

2021 ◽

Author(s):

Mateus Mittersteiner ◽

Helio G. Bonacorso ◽

Marcos A. P. Martins ◽

Nilo Zanatta

Keyword(s):

Biologically Active ◽

Regioselective Synthesis ◽

Enol Ethers

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Saegusa Oxidation of Enol Ethers at Extremely Low Pd-Catalyst Loadings under Ligand-free and Aqueous Conditions: Insight into the Pd(II)/Cu(II)-Catalyst System

The Journal of Organic Chemistry ◽

10.1021/acs.joc.0c02987 ◽

2021 ◽

Author(s):

Quan Zhu ◽

Yunsong Luo ◽

Yongyan Guo ◽

Yushun Zhang ◽

Yunhai Tao

Keyword(s):

Catalyst System ◽

Pd Catalyst ◽

Enol Ethers ◽

Ligand Free ◽

Aqueous Conditions ◽

Insight Into

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ChemInform Abstract: A NOVEL SYNTHESIS OF α,β-UNSATURATED ALDEHYDES AND ESTERS BY DYE-PHOTOOXYGENATION OF METHYL ENOL ETHERS

Chemischer Informationsdienst ◽

10.1002/chin.197818124 ◽

1978 ◽

Vol 9 (18) ◽

Author(s):

G. ROUSSEAU ◽

P. LE PERCHEC ◽

J. M. CONIA

Keyword(s):

Enol Ethers ◽

Unsaturated Aldehydes ◽

Novel Synthesis

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Synthese neuer Pyridin-C-nukleoside der 2 ,3 -Didesoxyribose durch „inverse“ [4+2]-Cycloaddition Synthesis of Novel Pyridine-C-nucleosides of 2,3-Dideoxyribose by „Inverse“ [4+2]-Cycloaddition

Zeitschrift für Naturforschung B ◽

10.1515/znb-1997-0715 ◽

1997 ◽

Vol 52 (7) ◽

pp. 851-858 ◽

Cited By ~ 6

Author(s):

Gunther Seitz ◽

Johanna Siegl

Keyword(s):

Cycloaddition Reaction ◽

Alder Reaction ◽

Diels Alder ◽

The Novel ◽

Protecting Group ◽

Enol Ethers ◽

Inverse Electron Demand ◽

Diels Alder Reaction ◽

Cyclic Ketene Acetals

The anomeric imido esters 5 and 6, appropriate precursors for C-nucleoside synthesis, were prepared and utilized as heterodienophiles in a Diels-Alder reaction with inverse electron demand to yield the novel, protected 1.2.4-triazine C-nucleosides 8 and 9. They could be deprotected by treatment with 70% trifluoroacetic acid to furnish the free C-nucleosides 10 and 11. The triazine „aglycon“ of 8 contains an electron deficient diazadiene system, highly activated to react with various electron rich dienophiles such as enamines, enol ethers and several cyclic ketene acetals in an „inverse“ [4+2]-cycloaddition reaction. The Diels-Alder adducts spontaneously eliminate N2 and after follow-up reactions the O-TBDPS protected pyridine-C-nucleosides 13, 15, 17,19, 21 and 23 are formed. Removal of the protecting group by treatment with CF3CO2H /H2O leads to the corresponding 2’,3’-dideoxy-β-D-ribofuranosyl- pyridines.

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