ABSTRACT
The first example of an iodocyclisation reaction made recyclable by the use of an ionic liquid as the reaction medium is reported. Readily available 1-mercapto-3-alkyn-2-ols were smoothly converted into the corresponding 3-iodothiophenes (50-81% yields, 10 examples) when allowed to react with iodine (1-2 equiv.) in a proper ionic liquid, such as 1-ethyl-3-methylimidazolium ethyl sulfate (EmimEtSO4), as the solvent under mild reaction conditions (25 °C) and in the absence of an external base. The reaction medium can be recycled several times without significantly affecting the reaction outcome. Theoretical calculations have also been performed to investigate the role of the ionic liquid anion in the reaction.
Subject(s)
Alkynes/chemistry , Ionic Liquids/chemistry , Sulfhydryl Compounds/chemistry , Thiophenes/chemical synthesis , Cyclization , Molecular Structure , Thiophenes/chemistryABSTRACT
About two decades after Kobayashi's discovery in 1983 of a very mild way of generating highly reactive aryne intermediates, the synthetic community embraced o-(trimethylsilyl)aryl triflates as convenient and versatile aryne precursors for the synthesis of carbocycles and heterocycles, as well as natural products and pharmaceutically promising drug candidates. This review provides a comprehensive overview of the construction of heterocycles using Kobayashi's silylaryl triflate aryne precursors. It is organized according to the type of heterocycle generated.
ABSTRACT
An efficient and simple route to biologically and pharmaceutically important o-hydroxyaryl ketones, xanthones, 4-chromanones, and flavones has been developed utilizing readily available carboxylic acids and commercially available o-(trimethylsilyl)aryl triflates.
ABSTRACT
An efficient one-pot method for the synthesis of 2,3-disubstituted benzo[b]furans from commercially available 2-iodophenols, terminal acetylenes and aryl iodides has been developed utilizing Sonogashira reaction conditions. After an initial Sonogashira coupling of the 2-iodophenol with the terminal alkyne, cyclization involving the aryl iodide provides the 2,3-disubstituted benzo[b]furan in good to excellent yields. The use of microwave irradiation shortens the reaction times and minimizes the side products. This methodology is especially useful for the construction of libraries of highly substituted benzo[b]furans and their analogues.
ABSTRACT
A novel approach to 3-iodothiophenes by direct iodocyclization of alkynylthiol derivatives is presented. A variety of 1-mercapto-3-yn-2-ols 5 (readily available from alkynylation of the corresponding alpha-mercapto ketones or alpha-mercapto esters) were smoothly converted into the corresponding 3-iodothiophene derivatives 6 in good yields by reaction with molecular iodine in the presence of NaHCO(3) at room temperature in MeCN as the solvent.
Subject(s)
Sulfhydryl Compounds/chemistry , Thiophenes/chemical synthesis , Cyclization , Molecular Structure , Stereoisomerism , Thiophenes/chemistryABSTRACT
The electrophilic cyclization of 2-(1-alkynyl)benzamides affords high yields of cyclic imidates, instead of the previously reported isoindolin-1-ones, where cyclization proceeds on the oxygen of the carbonyl group rather than the nitrogen of the amide functionality. X-ray crystallography and spectroscopic techniques have been used to characterize the products. A correction is hereby provided in order to rectify the previous misassignment of structure.
Subject(s)
Alkynes/chemistry , Benzamides/chemistry , Imidoesters/chemistry , Crystallography, X-Ray , Cyclization , Molecular Structure , StereoisomerismABSTRACT
The palladium-catalyzed annulation of arynes by substituted o-halobenzamides produces N-substituted phenanthridinones in good yields. This methodology provides this important heterocyclic ring system in a single step by simultaneous C-C and C-N bond formation, under relatively mild reaction conditions, and tolerates a variety of functional groups.
Subject(s)
Benzamides/chemistry , Fluorenes/chemical synthesis , Hydrocarbons, Halogenated/chemistry , Palladium/chemistry , Phenanthridines/chemical synthesis , Catalysis , Cyclization , Fluorenes/chemistry , Molecular Structure , Phenanthridines/chemistryABSTRACT
N-Acylcarbazoles have been synthesized in moderate to good yields by the annulation of in situ generated arynes with 2-haloacetanilides in the presence of a palladium catalyst and CsF. Both C-C and C-N bonds are formed simultaneously, and a variety of functional groups are tolerated in this reaction.
Subject(s)
Acetanilides/chemistry , Benzene/chemistry , Carbazoles/chemistry , Carbazoles/chemical synthesis , Palladium/chemistry , Catalysis , Substrate SpecificityABSTRACT
A variety of substituted benzisoxazolines have been synthesized by the [3 + 2] cycloaddition of nitrones and arynes. The reaction scope is broad, the reaction conditions are mild, and the process tolerates a variety of functional groups.
Subject(s)
Benzene Derivatives/chemistry , Isoxazoles/chemical synthesis , Nitrogen Oxides/chemistry , Cyclization , Isoxazoles/chemistry , Molecular Structure , StereoisomerismABSTRACT
A novel, efficient route to biologically and pharmaceutically important o-(dimethylamino)aryl ketones, acridones, acridinium salts, and 1H-indazoles has been developed starting from readily available hydrazones of aldehydes and o-(trimethylsilyl)aryl triflates. The reaction proceeds through arynes under mild conditions, tolerates a wide range of functional groups, and provides the final products in good to excellent yields.
Subject(s)
Acridines/chemical synthesis , Benzene Derivatives/chemistry , Hydrazones/chemistry , Indazoles/chemical synthesis , Ketones/chemical synthesis , Salts/chemistry , Acridines/chemistry , Acridones , Chemistry Techniques, Synthetic , Cyclization , Halogenation , Imines/chemistry , Indazoles/chemistry , Ketones/chemistry , Nitriles/chemistryABSTRACT
N-Unsubstituted ß-lactams react with a molecule of aryne by insertion into the amide bond to form a 2,3-dihydroquinolin-4-one, which subsequently reacts with another molecule of aryne to form an acridone by extrusion of a molecule of ethylene. 2,3-Dihydroquinolin-4-ones react under the same reaction conditions to afford identical results. This is the first example of ethylene extrusion in aryne chemistry.
Subject(s)
Acridones/chemical synthesis , Alkynes/chemistry , Ethylenes/chemistry , Quinolones/chemistry , beta-Lactams/chemistry , Acridones/chemistry , Molecular Structure , StereoisomerismABSTRACT
Pyrido[1,2-a]indoles are known as medicinally and pharmaceutically important compounds, but there is a lack of efficient methods for their synthesis. We report a convenient and efficient route to these privileged structures starting from easily accessible 2-substituted pyridines and aryne precursors. A small library of compounds has been synthesized utilizing the developed method, affording variously substituted pyrido[1,2-a]indoles in moderate to good yields.
Subject(s)
Amines/chemical synthesis , Indoles/chemical synthesis , Malonates/chemical synthesis , Amines/chemistry , Indoles/chemistry , Malonates/chemistry , Molecular StructureABSTRACT
The reaction of readily accessible 1,1-dialkylhydrazones with commercially available o-(trimethylsilyl)aryl triflates provides a direct one-step route to pharmaceutically important 1-alkylindazoles. The products are obtained in high yields by one-pot NCS-chlorination/aryne annulation or Ac(2)O-acylation/deprotection/aromatization protocols.
Subject(s)
Hydrazones/chemistry , Indazoles/chemical synthesis , Alkylation , Cyclization , Molecular StructureABSTRACT
The aryne [3 + 2] cycloaddition process with pyridinium imides breaks the aromaticity of the pyridine ring. By equipping the imide nitrogen with a sulfonyl group, the intermediate readily eliminates a sulfinate anion to restore the aromaticity, leading to the formation of pyrido[1,2-b]indazoles. The scope and limitation of this reaction are discussed. As an extension of this chemistry, N-tosylisoquinolinium imides, generated in situ from N'-(2-alkynylbenzylidene)-tosylhydrazides via an AgOTf-catalyzed 6-endo-dig electrophilic cyclization, readily undergo aryne [3 + 2] cycloaddition to afford indazolo[3,2-a]-isoquinolines in the same pot, offering a highly efficient route to these potential anticancer agents.
Subject(s)
Imides/chemistry , Indazoles/chemistry , Isoquinolines/chemistry , Phenazopyridine/chemistry , Sulfur Compounds/chemistry , Cyclization , Molecular Structure , Nitrogen/chemistryABSTRACT
A study of the nucleophilic addition of amines to 2,3-pyridyne has been carried out. 2-Aminopyridines have been generated exclusively. A series of benzonaphthyridinones have been synthesized by reacting 2,3-pyridyne and o-aminobenzoates.
ABSTRACT
The reaction of o-(trimethylsilyl)aryl triflates, CsF, and o-hydroxychalcones affords a general and efficient way to prepare biologically interesting 9-substituted xanthenes. This chemistry presumably proceeds by tandem intermolecular nucleophilic attack of the phenoxide of the chalcone on the aryne and subsequent intramolecular Michael addition. The introduction of an external base, Cs(2)CO(3), has proven beneficial in this reaction.
ABSTRACT
N-Arylisatins are efficiently prepared by the reaction of 2-oxo-2-(arylamino)acetates and arynes under mild reaction conditions.
Subject(s)
Acetates/chemistry , Isatin/chemical synthesis , Benzene Derivatives/chemistry , Methylation , Molecular StructureABSTRACT
A rapid and efficient synthesis of 2H-indazoles has been developed using a [3 + 2] dipolar cycloaddition of sydnones and arynes. A series of 2H-indazoles have been prepared in good to excellent yields using this protocol, and subsequent Pd-catalyzed coupling reactions can be applied to the halogenated products to generate a structurally diverse library of indazoles.
Subject(s)
Indazoles/chemical synthesis , Sydnones/chemistry , Catalysis , Hydrocarbons, Halogenated/chemistry , Indazoles/chemistry , Molecular Structure , Palladium/chemistry , StereoisomerismABSTRACT
The [3 + 2] cycloaddition of arynes with N-tosylpyridinium imides, followed by an elimination of Ts(-), affords pyrido[1,2-b]indazoles under mild reaction conditions in good yields.
Subject(s)
Imides/chemistry , Indazoles/chemical synthesis , Pyridinium Compounds/chemistry , Catalysis , Cyclization , Molecular Structure , StereoisomerismABSTRACT
Waterborne castor oil-based polyurethane-silica nanocomposites with the polymer matrix and silica nanoparticles chemically bonded have been successfully prepared through a sol-gel process. The formation of silica nanoparticles in water not only reinforces the resulting coatings, but also increases the crosslink density of the nanocomposites. The (29)Si solid state NMR spectrum indicates the formation of silica and the TEM indicates that the nanoparticles are embedded in the polymers, resembling a core-shell structure. The silica nanoparticles in the polymer matrix play an important role in improving both the mechanical properties and the thermal stabilities of the resulting nanocomposites. This work provides an effective and promising way to prepare biorenewable, high performance nanocomposite coatings.