Synthesis of dihydrofurans containing trifluoromethyl ketone and heterocycles by radical cyclization of fluorinated 1,3-dicarbonyl compounds with 2-thienyl and 2-furyl substituted alkenes

Manganese(III) acetate based radical cyclization of various fluorinated 1,3-dicarbonyl compounds with 2-thienyl and 2-furyl substituted alkenes produced 3-trifluoroacetyl and 2-trifluoromethyl-dihydrofurans in good yields. The radical cyclizations of 2-methyl-5-[(E)-2-phenylvinyl]furan 2b and 2-[(E)-2-phenylvinyl]thiophene 2c led to the formations of 5-(5-methyl-2-furyl)-4,5-dihydrofuran and 5-(2-thienyl)-4,5-dihydrofuran, respectively. In the reactions of 1,3-dicarbonyls with alkenes, 2-thienyl substituted alkenes formed 4,5-dihydrofurans in higher yields than 2-furyl substituted alkenes.     

Pyrroles from ketoximes and acetylene. 41. Some reactions of 1-vinyl-2-(2-furyl)- and-(2-thienyl)pyrroles

We have studied the reaction of 1-vinyl-2-(2-furyl)- and -(2-thienyl)pyrroles with trifluoroacetic anhydride, with hydrogen in the presence of catalysts (Raney nickel, palladium black, palladous chloride), with propargyl alcohol in electrophilic conditions [catalysis by perfluorobutyric acid in the system azoisobutyrodinitrile (AIBN)-CCl₄), and with alkane thiols with AIBN initiation. The products are novel substituted hetarylpyrroles.See [1] for Communication 40.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 337–342, March, 1991.     

Synthesis of carotenoid analogues having pyridine,furan, and thiophene rings as terminal groups

Heteroaromatic carotenoid analogues having 2-pyridyl, 3-pyridyl, 2-furyl, 3-furyl, 2-thienyl, and 3-thienyl groups at both the ends of tetramethyloctadecanonaene chain, were synthesized and their spectral properties were examined.     

Synthesis and properties of 2-(2-furyl)-and 2-(2-Thienyl)-1,3-benzoxazoles

Condensation of o-aminophenol with furoyl and thenoyl chlorides in 1-methylpyrrolidin-2-one gave, respectively, 2-(2-furyl)- and 2-(2-thienyl)-1,3-benzoxazoles in which the furan and thiophene rings showed no acidophobic properties. Reactions of 2-(2-furyl)- and 2-(2-thienyl)-1,3-benzoxazoles with electrophilic reagents (acylation, bromination, nitration, and sulfonation) afforded products of hydrogen replacement in both hetaryl and benzene rings, depending on the conditions.     

Base cleavage of substituted [phenyl(2-thienyl)methyl]- and [phenyl(2-furyl)methyl]-trimethylsilane. Stabilization of carbanionic centres by 2-thienyl and 2-furyl groups

Rates of cleavage by NaOMEMeOH at 25°C have been determined for (2-thienyl)₂CHSiMe₃ and for the compounds Ph(2-thienyl)CHSiMe₃ and Ph(2-furyl)CHSiMe₃ and some of their derivatives with a substituent in the m- or p-position of the phenyl group or the 5-position of the heterocyclic group. The results indicate that the 2-thienyl and 2-furyl groups stabilize a carbanionic centre more effectively than a phenyl group, and the following approximate pK_a values can be derived: Ph₂CH₂, 33.4; Ph(2-thienyl)CH₂, 30.0; Ph(2-furyl)CH₂, 29.6; (2-thienyl)₂CH₂, 27.1. The effect of the 2-Cl substituent in the thiophen ring is close to that of the p-Cl substituent in the benzene ring, and the effects of the p-Me substituents on the benzene ring are very close to those of the 2-Me substituents on the thiophen or furan rings. The product and rate isotope effects (determined by use of MeOD) are consistent with separation of the carbanion in the rate-determining step.     

Synthesis of Certain S-Triazole and s-Triazolo[3,4-B] 1,3,4-Thiadiazole Derivatives of Expected Pharmacological Activity

Reaction of the newly prepared 3-(2-thienyl)-4-amino-s-triazole-5-thione (I) with different alkyl kalides and aromatic aldehydes afforded the corresponding thioethers and arylidene derivatives (II and III), respectively. Attempt ring closure of (I) with acetic anhydride produced the unexpected triacetyl derivative (IV). The synthesis of certain 3-(2-thienyl)-6-substituted-s-triazolo[3,4-b] 1,3,4-thiadiazoles (V and VII) was described. IR, NMR and mass spectral analyses of the prepared compounds were discussed.     

Synthesis and Properties of 2-(2-Furyl)- and 2-(2-Thienyl)-1-methylphenanthro[9,10-d]imidazoles

Condensation of 9,10-phenanthrenequinone with 2-furaldehyde and 2-thiophenecarbaldehyde in glacial acetic acid in the presence of ammonium acetate gave 2-(2-furyl)- and 2-(2-thienyl)phenanthro[9,10-d]imidazoles which were converted into the corresponding 1-methyl derivatives. The furan and thiophene rings in the products lose their acidophobic properties. Depending on the conditions, electrophilic substitution reactions in 2-(2-furyl)- and 2-(2-thienyl)phenanthro[9,10-d]imidazoles occur both at the furan (thiophene) and phenanthrene moieties.     

THE CHEMISTRY OF HETEROARYLPHOSPHORUS COMPOUNDS. PART XII.1 THE DIFFERENTIAL-PULSE POLAROGRAPHIC REDUCTION OF HETEROARYL-AND HETEROARYLMETHYLPHOSPHONIUM SALTS

Abstract

The polarographic reduction of series of heteroaryl- and heteroarylmethylphosphonium salts has been studied using a differential pulse polarographic technique, this having a number of advantages over classical dc polarography. For the salts Ar₃P⁺CH₂PhBr^-, the observed order of ease of reduction correlates with the electron-withdrawing ability of the heteroaryl group (i.e. Ar = 2-furyl > 2-thienyl > phenyl > 1-methylpyrrol-2-yl). In contrast, for the salts Ph₃P⁺CH₂ArBr^- (Ar = 2-furyl, 2-thienyl, phenyl, 1-methylpyrrol-2-yl, 3-thienyl and 3-furyl), the ease of reduction correlates best with the order of stability of the forming carbanions as established in earlier studies of the alkaline hydrolysis of these salts.     

Furan ring opening–indole ring closure: SnCl2-induced reductive transformation of difuryl(2-nitroaryl)methanes into 2-(2-acylvinyl)indoles

A simple and efficient method for the synthesis of 2-(2-acylvinyl)-3-(5-alkyl-2-furyl)indoles by reductive recyclization of bis(5-alkyl-2-furyl)(2-nitroaryl)methanes is reported. This transformation was carried out by heating the substrates with SnCl₂·2H₂O in ethanol. The intermediate nitrosoarene moiety interacted with the furan ring via electrophilic nitrogen attack onto the C(2) position of the furan ring. It was shown that the related bis(5-alkyl-2-thienyl)(2-nitroaryl)methanes under the same reaction conditions failed to undergo the analogous recyclization and were transformed into bis(5-alkyl-2-thienyl)(2-aminoaryl)methanes.     

Inclusion complexes of prochiral heterocyclic ketones with β-cyclodextrins and their reduction with sodium borohydride

Alkyl(2-furyl), alkyl(2-thienyl), and methyl pyridyl ketones form stoichiometric inclusion complexes with -cyclodextrins. Reduction of these complexes in aqueous solution of Na₂CO₃ at room temperature yields the corresponding secondary alcohols with an optical yield which attains 27%.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1621–1627, December, 1993.     

Oxidative cyclization of 3-oxopropanenitriles with α,β-unsaturated amides by manganese(III) acetate. Regio- and stereoselective synthesis of 4-cyano-2,3-dihydrofuran-3-carboxamides

4-Cyano-2,3-dihydrofuran-3-carboxamides were obtained from the oxidative cyclization of 3-oxopropanenitriles with unsaturated amides using manganese(III) acetate. Treatment of 3-oxopropanenitriles with (2E)-3-(5-methyl-2-furyl)acrylamide and (2E)-3-(2-thienyl)acrylamide gave 2-(5-methyl-2-furyl) and 2-(2-thienyl) substituted 4-cyano-2,3-dihydrofuran-3-carboxamides in moderate yields, respectively. However, (2E)-3-(2-furyl)acrylamide and (2E)-3-phenylacrylamide did not produce any product under the same conditions. On the other hand, reaction of a dienamide such as (2E,4E)-5-phenylpenta-2,4-dienamide with 3-oxopropanenitriles gave diastereomeric mixtures of 2-(2-vinylphenyl)-4-cyano-2,3-dihydrofuran-3-carboxamides. Mechanisms are proposed for the formation of all of these compounds.     

Greenish metal-lustrous organic crystals formed from 1-aryl-2-(2-thienyl)-5-(5-tricyanoethenyl-2-furyl)pyrroles

On the treatment of 1-aryl-2-(2-furyl)-5-(2-thienyl)pyrroles with tetracyanoethylene, 1-aryl-2-(2-thienyl)-5-(5-tricyanoethenyl-2-furyl)pyrroles were produced. These compounds formed crystals with greenish metallic luster. In their solid-state UV-vis-NIR diffuse reflection-absorption spectra, absorption band corresponding to metallic reflection spreads in the range of 550-900 nm. Furthermore, strong absorption appeared below 520-540 nm. This absorption results in the appearance of green color. Single-crystal X-ray crystallographic analysis revealed the crystal structure of 1-(4-methoxyphenyl)-2-(2-thienyl)-5-(5-tricyanoethenyl-2-furyl)pyrrole (2c). The distinct features of the crystal structure are as follows: (1) the thiophene-pyrrole-furan-tricyanoethenyl π-system is approximately flat; (2) the conformational relation between the pyrrole ring and the furan ring is anti, that is, these rings are pointing in opposite directions and the dihedral angle of N-C-C-O=180°; (3) as a result, the tricyanoethenyl group is far from the 4-methoxyphenyl group; (4) the molecules of 2c are arranged in a ribbon structure; (5) the ribbons are assembled side-by-side to form a terraced layer; (6) the layers stack so that the π-orbitals of 2c become close to each other.     

Infrared spectra of thiophene analogs of chalcones and their vinylogs

The IR spectra of 45 thiophene analogs of chalcones and vinylogs, and (2-thienyl)phenylketone are determined in the 1700-650 cm^–1 region, and frequency assignments made. It is confirmed that the carbonyl group and aliphatic double bond are so situated with respect to one another that there is approximation to the S-cis form. It is shown that in the systems studied, 2-thienyl has an electron-donating effect, exceeding that of 2-furyl. It is also found that for 1-(2-thienyl)-3-arylpropen-1-ones the carbonyl group frequency shift due to substituents tends to correlate with the Hammett parameters.     

Reactions of benzoylheteroaroylmethanes with hydroxylamine hydrochloride

Benzoyl-2-furoylmethane reacts with hydroxylamine hydrochloride to give predominantly 5-(2-furyl)-3-phenylisoxazole and not as reported in the literature 3-(2-furyl)-5-phenylisoxazole. Benzoyl-2-thenoylmethane and benzoylpicolinoylmethane afforded 3-phenyl-5-(2-thienyl)isoxazole and 5-phenyl-3-(2-pyridyl)isoxazole respectively.     

An Amphiphilic Selenide Catalyst Behaves Like a Hybrid Mimic of Protein Disulfide Isomerase and Glutathione Peroxidase 7

Protein disulfide isomerase (PDI) and glutathione peroxidase 7 (GPx7) cooperatively promote the oxidative folding of disulfide (SS)‐containing proteins in endoplasmic reticulum by recognizing the nascent proteins to convert them into the native folds by means of SS formation and SS isomerization and by catalyzing reoxidation of reduced PDI with H₂O₂, respectively. In this study, new amphiphilic selenides with a long‐chain alkyl group were designed as hybrid mimics of PDI and GPx7 and were applied to the refolding of reduced hen egg‐white lysozyme (HEL‐R). Competitive SS formation at pH 4 using HEL‐R and glutathione (GSH) in the presence of the selenide catalyst and H₂O₂ showed that the amphiphilic selenides can preferentially catalyze SS formation of HEL‐R, probably on account of hydrophobic interactions between the protein and the catalyst. In contrast, simple water‐soluble selenides did not exhibit such behavior. In addition, when the pH of the solution was adjusted to 8.5 after the SS formation, surviving GSH promoted the SS isomerization of misfolded HEL to recover the native SS linkages. Thus, the amphiphilic selenides designed here could mimic the function of the PDI‐GPx7 system. The combination of a water‐soluble selenide and a long‐chain alkyl group would be a useful motif in designing medicines for both protein misfolding diseases and antioxidant therapy.     

Unsuccessful/successful attempts to produce penta(heteroaryl)-phosphoranes/-arsoranes R5E (E = P, As; R = 2-furyl, 2-thienyl)

Tri(2-thienyl)phosphine (1) has been transformed into chlorotri(2-thienyl)phosphonium chloride (3) in the reaction with hexachloroethane, into tetra(2-thienyl)phosphonium bromide (4) in a NiBr2-catalyzed quaternization with 2-bromothiophene, and into the p-tolylsulfonyliminotri(2-thienyl)phosphorane (6) using "chloramine T". Attempts to generate the homoleptic penta(2-thienyl)phosphorane (2-C4H3S)5P (5) by treating 3, 4, 6 or the known (PhO)3P=NSO2C6H4-2-Me (9) with 2-thienyllithium were unsuccessful. Tri(2-furyl)phosphine (2) was converted into the related imine 7, but the reaction of 7 or of 9 with 2-furyllithium failed to give (2-C4H3O)5P (8). It was only with the strained phosphorane Ph(C12H8)P=NSO2C6H4-4-Me (C12H8= 2,2'-biphenylylene) (10) that with 2-C4H3OLi the corresponding phosphorane Ph(C12H8)P(C4H3O-2)2 (11) could be obtained (31P NMR: delta-106.7 ppm). In the arsenic series, tri(2-thienyl)- and tri(2-furyl)arsine (12, 13) were converted into the tosylimino compounds (14, 15) and successfully transformed into the homoleptic arsoranes with 2-C4H3E-Li: penta(2-thienyl)- (16) and penta(2-furyl)-arsorane (17) are stable colourless crystalline solids, the NMR spectra of which indicate rapid pseudo-rotation in solution. The single crystal structure analysis of 17 shows an only slightly distorted trigonal-bipyramidal configuration. In crystals of the phosphine 2 and the arsine 13 the molecules have a propeller configuration with approximate C3v symmetry for the former, but Cs symmetry for the latter. The crystal structures of the precursors or intermediates 3, 4, 6, 9, and 10 have also been determined.     

Diastereoselective Diels-Alder Reaction of 2-Thienyl and 2-Furyl Substituted 3-Propenethioamides with Electron Deficient Dienophiles

Summary. The hetero-Diels-Alder reaction of N-aryl-3-(2-thienyl)-2-propenethioamides with N-phenylmaleimide and maleimide yielded a mixture of endo- and exo-2-arylimino-4-(2-thienyl)tetrahydrothiopyran[2,3-c]pyrroles. Cycloaddition to diethyl fumarate required acylation and furnished a mixture of diastereoisomeric 5-(N-acetylphenylamino)-2,3-bis-(ethoxycarbonyl)-4-(2-thienyl)-3,4-dihydro-2H-thiopyrans. Reactions of 3-(2-furyl)-2-propenethioamides with N-arylmaleimides furnished the correspondent 2-arylimino-4-(2-furyl)tetrahydrothiopyran[2,3-c]pyrroles. In the cycloadditions of the heterodienes with N-arylmaleimides the endo-cycloadducts were formed as the major products.     

PMR spectral study of the structure of 1-vinyl-2-(2-furyl)- and 2-(2-thienyl)pyrroles

Conclusions PMR spectral data indicate that the heterocycles in 1-vinyl-2-(2-fury1- and 1-vinyl-2-(2-thienyl) pyrroles lie in a single plane with syn arrangement of the heteroatoms and trans orientation of the vinyl group relative to the non-pyrrole heterocycle. Molecular coplanarity is lost in 3-alky1-1-vinyl-2-(2-furyl)- and 3-alkyl-1-vinyl-2-(2-thienyl) pyrroles.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 184–186, January.     

Pyrazine-2,3-dicarbonitriles substituted with maleimide derivatives

Syntheses and spectroscopic characteristics are reported for eight pyrazine-2,3-dicarbonitriles substituted with maleimide residue in addition to phenyl, 2-thienyl, or 2-furyl substituent. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1409–1414, September, 2007.     

β-(2-furyl and 2-thienyl)acroleins in reactions with vinyloxyanilines

Equimolecular amounts of-(2-furyl and 2-thienyl)acroleins and o-, m-, and p-vinyloxy-anilines react at room temperature to form-(2-furyl and 2-thienyl)acrylidinevinyloxy-anilines. Their structures were proved by hydrogenation, hydrolysis, and IR spectroscopy. Their capacity for complexing with hydrated stannic chloride was established. The bacteriostatic activity of some of the synthesized substances was tested.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1626–1630, December, 1971.