RESUMO
The difluorination reaction of alkenes catalyzed by molecular iodine was revealed for the first time. This difluorination reaction affords a simple and practical experimental method and can be applied to many aliphatic and aromatic alkenes bearing synthetically useful functional groups, such as ester, amide, hydroxy, and aryl groups. Preliminary mechanistic studies of this alkene difluorination suggest the existence of two catalytic cycles: the IF-driven cycle and the catalytic cycle by the IF adduct.
RESUMO
Fluorination reaction of alkenes with iodine and HF·pyridine complex (pyr·9HF) was performed under mild conditions in the presence of K2S2O8 or Na2S2O8 as an oxidant. Aliphatic and aromatic alkenes underwent iodofluorination to give the iodofluorinated products with high regioselectivity. The substitution reactions of the iodofluorinated product by nitrogen, sulfur, and oxygen nucleophiles indicated further applications as a building block for synthesis of 2-fluoroalkyl-substituted compounds.
RESUMO
This review article focused on the innovative procedure for electrophilic fluorination using HF and in situ generation of the required electrophilic species derived from hypervalent iodine compounds. The areas of synthetic application of this approach include fluorination of 1,3-dicarbonyl compounds, aryl-alkyl ketones, styrene derivatives, α,ß-unsaturated ketones and alcohols, homoallyl amine and homoallyl alcohol derivatives, 3-butenoic acids and alkynes.
Assuntos
Fluoretos/química , Flúor/química , Halogenação , Álcoois/química , Catálise , Ciclização , Ácido Fluorídrico/química , Cetonas/química , Estrutura Molecular , Estireno/químicaRESUMO
A new synthetic method for [1]benzothieno[3,2- b][1]benzothiophene derivatives (BTBTs) was developed. The present method consists of iodocyclization of 1,2-bis(2-methylthiophenyl)ethynes and photolysis of 3-iodo-(2-methylthiophenyl)benzo[ b]thiophenes. With 1,2-bis(2-methylthiophenyl)ethynes treated with I2/PhI(OAc)2 in CH2Cl2 at room temperature, selective cyclization at sulfur took place to give 3-iodo-(2-methylthiophenyl)benzo[ b]thiophenes in good yields. Irradiation of the iodinated benzo[ b]thiophenes with a high-pressure Hg lamp (>290 nm) provided BTBTs in good yields. Furthermore, the present method was applied to the synthesis of bis[1]benzothieno[2,3- d;2',3'- d']benzo[1,2- b;4,5- b']dithiophene (BBTBDT).
RESUMO
The hypervalent iodine/HF reagent consisting of PhIO and HF·py was found to be effective for fluorination of functionalized aromatic olefins bearing synthetically important carbonyl and hydroxyl groups. Fluorination of 1,3-diphenyl-2-propen-1-one with PhIO/HF·py reagent in CH2Cl2 at room temperature gave 3,3-difluoro-1,2-diphenyl-1-propanone in high yield. Other α-aryl-α,ß-unsaturated ketones underwent the fluorination to yield aryl 2,2-difluoroethyl ketone derivatives in good to high yields. Catalytic fluorination of α-aryl-α,ß-unsaturated ketones using a p-TolI/HF·py/mCPBA reagent system also worked well. Moreover, the fluorination of cinnamyl alcohol derivatives by PhIO/HF·py reagent proceeded smoothly to afford 2-aryl-3,3-difluoro-1-propanols in moderate yields.
RESUMO
The reaction of alkynes with PhIO and Py·HF followed by treatment with BF3·OEt2 gave ß-fluorovinyliodonium tetrafluoroborates in good to high yields. More conveniently, the reaction using PhI and Py·HF in the presence of m-CPBA also afforded ß-fluorovinyliodonium tetrafluoroborates in good yields. These methods have the advantages that ß-fluorovinyliodonium salts can be prepared without ArIF2.
RESUMO
The 1,4-benzdiyne equvalent, [2,5-bis(trimethylsilyl)-4-(trifyloxy)phenyl](phenyl)iodonium triflate, was prepared from sodium 2,4,5-trichlorophenoxide. The chemoselective generation of an aryne from the side of the phenyliodonio group was observed after treatment with a fluoride ion. Double cycloaddition of 1,4-benzdiyne with different arynophiles was conducted in one pot, giving bis-cycloadducts in high yields. Similarly, the 1,3-benzdiyne equivalent bearing phenyliodonio and triflate groups was prepared from sodium 2,3,6-trichlorophenoxide. The 1,3-benzdiyne equivalent also underwent the chemoselective stepwise generation of arynes and the double cycloaddition with different arynophiles. These hybrid benzdiyne equivalents provided the double cycloadducts in high yields and enabled the convenient one-pot procedure for synthesis of polycyclic aromatic compounds.
RESUMO
The intramolecular aminofluorination of homoallylamine derivatives using a reagent system of PhI(OAc)2 and Py·HF in CH2Cl2 at room temperature for 5 h gave N-tosyl-3-fluoropyrrolidines in good to high yields. Furthermore, the catalytic aminofluorination was furnished by the reaction using p-iodotoluene as a catalyst in the presence of Py·HF as a fluorine source and mCPBA as a terminal oxidant.
RESUMO
Fluorination of styrene derivatives with a reagent system composed of µ-oxo-bis[trifluoroacetato(phenyl)iodine] and a pyridine·HF complex gave the corresponding (2,2-difluoroethyl)arenes in good yields. Similarly, the reagent of PhI(OCOCF3)2 and the pyridine·HF complex acted as a fluorinating agent for styrene derivatives. The fluorination of styrene derivatives with the pyridine·HF complex underwent under catalytic conditions using 4-iodotoluene as a catalyst and m-CPBA as a terminal oxidant.
RESUMO
The direct fluorination reaction of acetophenone using iodosylarenes and TEA·5HF was conducted under mild conditions except for use of a HF reagent. The fluorination reaction was applied to acetophenone derivatives, acetonaphthones, benzyl phenyl ketone, propiophenone, butyrophenone, 1-indanone, and phenacyl chloride, giving selectively the corresponding α-fluoroketone derivatives in good yields.
Assuntos
Acetofenonas/síntese química , Etilaminas/química , Hidrocarbonetos Fluorados/química , Iodo/química , Acetofenonas/química , Halogenação , Indicadores e Reagentes/química , Estrutura MolecularRESUMO
A practical and safe synthesis of 1,2-bis(trimethylsilyl)benzene from 1,2-dichlorobenzene and Me3SiCl was achieved by use of a hybrid metal of Mg and CuCl in the presence of LiCl in 1,3-dimethyl-2-imidazolidinone (DMI). This method does not require a toxic HMPA, provides a high yield of the product under mild conditions, and is also applied to synthesis of substituted 1,2-bis(trimethylsilyl)benzenes and poly(trimethylsilyl)benzenes.
Assuntos
Derivados de Benzeno/síntese química , Cobre/química , Imidazóis/química , Cloreto de Lítio/química , Magnésio/química , Derivados de Benzeno/química , Estrutura MolecularRESUMO
Intramolecular hydroarylation of 4-benzofuranyl alkynoates using Pd(OAc)(2) as catalyst took place selectively and efficiently, giving angular furocoumarin derivatives in high yields. The parent angelicin was obtained in 80% yield by this method. The starting 4-benzofuranyl alkynoates were easily accessible from readily available 4-hydroxybenzofurans and alkynoic acids.
Assuntos
Alcinos/química , Benzofuranos/química , Furocumarinas/química , Furocumarinas/síntese química , Paládio/química , Catálise , Estrutura Molecular , EstereoisomerismoRESUMO
Reaction of dibenzoylmethane with (diacetoxyiodo)benzene in the presence of KOH in MeCN quantitatively gave the corresponding iodonium ylide, which was treated with a HF reagent to afford the corresponding 2-fluorinated dibenzoylmethane in 14-50% yields. The similar reaction of the iodonium ylides obtained from 1-phenylbutan-1,3-dione, ethyl benzoylacetate, and ethyl p-nitrobenzoylacetate with TEA·3HF gave the corresponding fluorinated products in 17-34% yields. It is suggested that the fluorinated products were formed through the C-protonation of the ylide, followed by displacement with fluoride ion. The same reaction of the iodonium ylide of dibenzoylmethane with concentrated HCl gave the corresponding chlorinated product in 45% yield.
Assuntos
Ácido Fluorídrico/química , Oniocompostos/química , Indicadores e ReagentesRESUMO
Phenyl(trimethylsilylethynyl)iodonium and tert-butyldimethylsilylethynyl(phenyl)iodonium triflates were applied to alkynylation of benzotriazole. Treatment of the silylethynyliodonium triflates with the potassium salt of benzotriazole ion in (t)BuOH and CH(2)Cl(2) gave 2-(trimethylsilylethynyl)-2H-1,2,3-benzotriazole and 2-(tert-butyldimethylsilylethynyl)-2H-1,2,3-benzotriazole in 74% and 76% yields, respectively. The regioisomers, 1-silylethynyl-1H-1,2,3-benzotriazole derivatives, were minor. In both cases of the silyl-substitued ethynyliodonium salts, novel regioselective alkynylation of benzotriazole at the 2 position was observed.
RESUMO
Iodoarylation of arylacetylenes was performed using a simple reagent system composed of molecular iodine and [bis(benzoyloxy)iodo]benzene. Most arylacetylenes efficiently underwent the iodoarylation reaction with electron-rich arenes to give trans 1,1-diaryl-2-iodoethene adducts regio- and stereoselectively. As an exception, the iodoarylation of p-methoxyphenylacetylene resulted in a mixture of E- and Z-isomers of the corresponding product.
Assuntos
Alcinos/química , Halogenação , Iodo/química , Indicadores e Reagentes/químicaRESUMO
Palladium complexes with bidentate phosphine ligands, Pd(dppe)(OAc)(2) and Pd(dppm)(OAc)(2), were found to be effective catalysts for reactions of simple arenes with ethyl propiolate, affording arylbutadiene derivatives selectively.
RESUMO
A strategy for desilylative acetoxylation of (trimethylsilyl)arenes has been developed in which (trimethylsilyl)arenes are converted into acetoxyarenes. The direct acetoxylation is performed in the presence of 5 mol % of Pd(OAc)2 and PhI(OCOCF3)2 (1.5 equiv) in AcOH at 80 °C for 17 h. The acetoxyarenes are obtained in good to high yields (67-98%). The synthetic utility is demonstrated with a one-pot transformation of (trimethylsilyl)arenes to phenols by successive acetoxylation and hydrolysis. Furthermore, desilylative acyloxylation of 2-(trimethylsilyl)naphthalene using several carboxylic acids has been conducted.
RESUMO
A simple, practical, and convenient fluorination of 1,3-dicarbonyl compounds was achieved by direct use of aqueous hydrofluoric acid and iodosylbenzene (PhIO). The reaction of ethyl benzoylacetate with the reagent system of aqueous HF and PhIO in CH(2)Cl(2) gave ethyl 2-fluoro-2-benzolyacetate in 98% yield. Other 1,3-dicarbonyl compounds including ß-keto esters and 1,3-diketones underwent the fluorination reaction to give the corresponding fluorinated products in good yields.