Cross-dehydrogenative coupling of secondary benzylic ethers with indoles and pyrroles

Current studies on cross-dehydrogenative coupling of benzylic ethers for new C–C bond construction predominantly focus on primary ether moieties. Oxidative cross-coupling of secondary benzylic ethers remains elusive. Herein, we describe the first cross-dehydrogenative coupling of secondary benzylic ethers with indoles and pyrroles for tertiary ether construction. A broad range of α-aryl substituted isochromans react with a variety of electronically varied indoles and pyrroles smoothly under mild metal-free conditions in high efficiency. In addition, the catalytic asymmetric variant was preliminarily explored, and corresponding tertiary ether was obtained in 69% ee.     

Novel and facile synthesis of fluorinated enamino ketones and amino alcohols

Selected imines and one bis-imine react via their enamine tautomers with terminal perfluorinated epoxides, e.g. hexafluoropropene oxide to produce fluorinated enamino ketones or imino ketones. In contrast, internal perfluorinated linear epoxides and one cyclic epoxide yield intermediate imino alcohols, which in one case added hexafluoroacetone, furnishing a new imino diol investigated by X-ray diffraction.     

Microwave-assisted catalyst-free synthesis of tetrasubstituted pyrroles using dialkyl acetylenedicarboxylates and monophenacylanilines

An efficient catalyst-free microwave-assisted synthesis of tetrasubstituted pyrroles using dialkyl acetylenedicarboxylates and substituted monophenacylanilines has been developed. Axial chirality has been noticed in some N-(α-naphthyl/2-isopropylphenyl)-2,3-dicarbethoxy-4-arylpyrroles, but not with N-aryl-2,3-dicarbethoxy-4-(α-naphthyl)pyrrole.     

Modular one-pot synthesis of tetrasubstituted pyrroles from alpha-(alkylideneamino)nitriles

2,3,4,5-Tetrasubstituted pyrroles have been prepared with high regioselectivity by a formal cycloaddition of alpha-(alkylideneamino)nitriles and nitroolefins followed by elimination of HCN and HNO2. The reaction allows the convergent construction of the pyrrole ring in four steps from a nitroalkane and three aldehydes.     

Novel photochemical reactions of enamino ketones

Irradiation of the conjugated N-aryl enamino ketone (V) yielded the indole (VI) resulting from a novel decomposition of the ylide intermediate.     

A new approach to the synthesis of 1,2,3,5‐tetrasubstituted pyrroles

2‐Propargyl‐1,3‐dicarbonyl derivatives, namely the corresponding cumulenes and diethoxyphosphoryloxy containing substances in the reactions with primary amines, are converted into the corresponding 1,2,3,5‐tetrasubstituted pyrroles. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:220–225, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20265     

Conformational study of chiral cisoid enamino ketones

A study of a number of chiral cisoid cyclic enamino ketones by the circular dichroism method showed that they contain an inner disymmetric chromophore. The presence of homoconjugation of the phenyl and enamino ketone chromophores as a result of the drawing together of their orbitals in space was also established.Communication XXXVI from the series Stereochemical Studies; see [1] for communication XXXVTranslated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 511–515, April, 1976.     

Synthesis of enamino ketones from 4,5-dihydropyrazoles

Enamino ketones were synthesized in 97–99% yield by reactions of 4,5-dihydropyrazoles with 1,3-dicarbonyl compounds.     

One-pot,three-component cascade synthesis of new tetrasubstituted pyrroles by coupling reaction of 2-functionally substituted 2-alkenals,amines, and nitroethane

The reactivity of 2-alkylthio(2-alkoxy)-substituted 3-aryl(hetaryl)propenals in a one-pot, three-component reaction with primary amines and nitroethane has been studied. A method for the synthesis of highly functionalized pyrroles (in 36–80% yield) from 2-alkylthiopropenals has been developed on the basis of this reaction. It is found that the reaction proceeds via formation of the intermediate imine of the starting enal, which undergoes 1,2-addition by nitroethane to give kinetically controlled 2-alkylthio-3-alkylamino-1-aryl(hetaryl)-4-nitropentene. When left to stand, upon heating or under microwave assistance, this adduct can be transformed into the thermodynamically controlled 1,4-adduct. The latter undergoes intramolecular cyclization to afford the target pyrrole. A possibility of such isomerization of addition products of nitroalkane to 2-functionalized α,β-unsaturated imines is revealed for the first time. Scope of the reaction depending upon its conditions as well as structure of the starting substrates and amines has been studied.     

Conformational study of chiral heterocyclic enamino ketones

An assumption regarding the existence of a homoconjugation effect involving enaminoketo and phenyl groups as a result of the drawing together in space of their orbitals was made on the basis of circular dichroism (CD) data and an examination of the preferred conformations of two-ring enamino ketones with -phenylethyl and -benzylethyl substituents. A study of enamino ketones with a chiral alkyl substituent attached to the nitrogen atom made it possible to confirm this assumption.Communication XLIX from the series Stereochemical Studies. See [1] for communication XLVIII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1230–1233, September, 1978.     

Synthesis and rotatory dispersion of cisoid bicyclic enamino ketones

Optically active cisoid, bicyclic, enamino ketones — N-(-phenylethyl)-4-keto-^9,10-octa-hydroquinoline and N-(-phenylethyl)-4-keto-^8,9-hexahydropyridine — were synthesized by the condensation of ethyl -[N-(-phenylethyl)amino]propionate with cyclohexanone and cyclopentanone, while ethyl -(N-benzylamino)propionate and cyclohexanone gave N-benzyl-4-keto-^9,10-octahydroquinoline. A study of the rotatory dispersion of the compounds obtained demonstrated that a strong positive Cotton effect at 330–350 nm, which is associated with the presence of a cis-enamino ketone chromophore, is characteristic for them.Communication XXVIII of the series Stereochemical Investigations. See [1] for communication XXVII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 541–545, April, 1972.     

Single-isomer tetrasubstituted olefins from regioselective and stereospecific palladium-catalyzed coupling of beta-chloro-alpha-iodo-alpha,beta-unsaturated esters

The efficient regioselective and stereospecific synthesis of tetrasubstituted olefins using a mild and convenient method is disclosed. 2-Alkynyl esters are selectively converted to E-beta-chloro-alpha-iodo-alpha,beta-unsaturated esters by exposure to Bu4NI in refluxing dichloroethane. These products are produced cleanly, regio- and stereoselectively, and in high yields. Single-isomer tetrasubstituted olefins bearing four different carbon substituents are then synthesized by sequential palladium-catalyzed coupling reactions. Selectivity results from reactivity differences in the intermediate substrates.     

An improved synthesis of pyrroles from N-p-toluenesulfonylglycine esters and α,β-unsaturated aldehydes and ketones

N-p-Toluenesulfonylglycine esters 2 condensed with α,β-unsaturated carbonyl compounds 1 in the presence of the non-nucleophilic base DBU to give hydroxypyrrolidines 3 . Dehydration with phosphorus oxychloride-pyridine, followed by DBU mediated elimination of p-toluenesulfinic acid, gave a series of synthetically useful pyrrole-2-carboxylates 5 .     

Oxidative free radical reactions of enamino esters

Oxidative free radical reactions of enamino esters are described. Electrophilic carbon-centered radicals produced by the cerium(IV) ammonium nitrate (CAN) oxidation of β-dicarbonyl compounds undergo efficient addition to the C-C double bond of enamino esters. This CAN mediated free radical reaction between enamino esters and β-dicarbonyl compounds provides a novel method for the synthesis of highly substituted pyrroles. The direct CAN oxidation of β-enaminocinnamates gave the dimerization products effectively.     

Synthesis of substituted pyrroles from ketones

A number of substituted pyrroles have been prepared through a four step reaction sequence based on the regiospecific alkylation of N,N-dimethylhydrazones with 2-iodomethyl-1,3-dioxolane.