Study of furan compounds

The electrolytic alkoxylation of several furan aldehydes and ketones was accomplished. It is shown that the electrolytic methoxylation of the aldehydes is an intramolecular reaction and leads to compounds of the 2,7-dimethoxy-1,6-dioxaspiro[4.4]-3-nonene series. Depending on the conditions, 2,7-dimethoxy-1,6-dioxaspiro[4.4]nonanes and 1,6-dioxaspiro [4.4]-nonanes were synthesized by the catalytic hydrogenation of the latter. The corresponding -carbonyl-containing 2,5-dimethoxy-2,5-dihydrofurans are formed in the case of the methoxylation of the furan ketones.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1155–1158, September, 1971.     

Researches on condensation products of some 2, 2′-dithieniyl compounds. I

Crotonaldehyde-type condensation of 5-acetyl-2, 2-dithienyl with some aromatic and heterotyclic aldehydes and nitroaldehydes in the presence of alkali is used to synthesize a number of hitherto undescribed unsaturated 2, 2-dithienyl ketones. The visible and UV absorption spectra of these compounds of the ketones synthesized are measured in ethanol and 96% sulfuric acid solutions. In sulfuric acid all the compounds investigated form intensely colored halochromic solutions. Comparison of the spectral characteristics of the compounds prepared shows that replacement of the benzene ring by furan and thiophene rings gives rise to a bathochromic effect which is significantly greater in acid solution than in neutral solution. For the neutral solution, introduction of a single nitro group into the benzene or thiophene ring gives rise to a K-band bathchromic shift, while in acid solution there is a hypsochromic effect.     

Decarbonylation of furfural over oxide catalysts

Gas chromatography has been used to investigate the products accompanying tetrahydrofuran prepared by hydrogenation of furan, without isolating the latter pure from the gas mixture obtained by decarbonylating furfural over oxide catalysts. A number of unknown impurities accompanying tetrahydrofuran and furan, are identified. It is found that tetrahydrofuran contains isopropanol, along with furan,-methylfuran, and-methyltetrahydrofuran. Furan itself contains-methylfuran, and a number of unknown impurities, among them acetone. Ethane is found among the gaseous products of decarbonylation. Thus over Zn and Mn oxide catalysts there is joint hydrogenolysis of the furan ring, and ring opening at positions 1–5 and 3–4.     

Chemistry of oxalyl derivatives of methyl ketones. 28. Reaction of carbonyl compounds of adamantane with 5-phenyl-2,3--dihydrofuran-2,3-dione

The reaction of substituted methyl 1-adamantyl ketones with an equimolar amount of 5-phenyl-2,3-dihydrofuran-2,3-dione under the conditions of the thermal decarbonylation of the latter leads to the corresponding 2-methyl-2-adamantyl-6-pheny1-1,3-dioxen-4-ones, 6-phenyl-3-benzoyl-2,4-dione, and the starting ketones. The steric and electronic factors that affect the yields of the dioxen-4-ones were examined. -Hydroxymethyl 1-adamantyl ketones open up the furan ring to give 1-adamantoylmethyl benzoylpyruvate. Data from the IR, PMR, and UV spectra are presented.See [1] for communication 27.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1312–1315, October, 1982.     

Ruthenium(II)-catalyzed para-selective CH difluoroalkylation of aromatic aldehydes and ketones using transient directing groups

A Ru(II)-catalyzed para-difluoroalkylation of aromatic aldehydes and ketones with a transient directing group has been developed. It utilizes less expensive ruthenium catalysts and allows facile access to challenging difluoroalkylated aldehydes. The mechanism studies suggest that the distinct coordination mode of ruthenium complex with imine moieties is responsible for para-selectivity.     

Synthesis of 9-R1-10-R-1,8-Dioxodecahydroacridines and Dioximes Based on Them

3,3,6,6-Tetramethyl-9-R¹-10-R-1,8-dioxo-1,2,3,4,5,6,7,8,9,10-decahydroacridines were synthesized through the intermediate -R-methylenebisenamino ketones by the condensation of 5,5-dimethyl-3-N-R-aminocyclohex-2-enones with aliphatic, aromatic, and furan aldehydes (2-propanol, phosphorus pentoxide). It was found that the degree of substitution of the heterocycle in decahydroacridinediones has an effect on the direction of their transformations during oximation.     

Saturated nitrogen heterocyclic compounds

Results are given of research on the synthesis of-pyrrolidylalkan-3-ols by hydrogenating primary and secondary furan amines under pressure over Raney nickel in aqueous acid solution. Some views about the mechanism of the reaction are put forward. It is shown that the relative yields of the-pyrrolidylalkan-3-ols and corresponding tetrahydrofuran amines depend both on structural peculiarities of the starting furan amine, and on the hydrogenation conditions.     

Synthesis of oxoacids and oxoesters of the furan series

Summary ß-(Furyl-2)propionic acid and its methyl and ethyl esters add in acid medium to ,ß-unsaturated aldehydes and ketones, forming oxoacids and oxoesters of the furan series.     

Research on furan compounds

Pressure hydrogenation using Raney nickel or ruthenium on charcoal, of secondary and tertiary -furylalkanols is described. The products are the corresponding homologs of 1, 6-dioxaspiro[4, 4]nonane and tetrahydrofuran alcohols, the relative yields being determined by the structure of the initial furan alcohol and the type of catalyst.For Part XXXII see [1].     

Activity of catalysts in thiophene synthesis from furan and hydrogen sulfide

Thiophene synthesis from furan and H₂S over acid catalysts is reported. Proton donor catalysts are low-active, nonselective, and prone to deactivation. Alumina-supported catalysts having Lewis acid sites, such as alumina-supported catalysts, are more efficient. With these catalysts, the thiophene formation rate per Lewis acid site increases with increasing site strength. It is assumed that the reaction proceeds via the formation of a surface intermediate consisting of an acid site bonded to an α carbon atom of the furan ring and an H₂S molecule nondissociatively adsorbed on a basic site. At atmospheric pressure, T = 250–450°C, initial furan concentrations of 1–20 vol %, and H₂S/furan = 0.4–20 (mol/mol), the thiophene formation reaction is first-order with respect to both reactants and its rate constant increases with increasing temperature. The thiophene formation rate depends on the H₂S/furan molar ratio. Under optimal conditions, the thiophene yield is 95–98 mol % and the thiophene formation rate is high.     

Synthesis of pyrido [1',2':4,3 ]-s-triazolo[1,5-a]-pyrimidinium salts

Pyrido[l',2':4,3]-s-triazolo[1,5-a]pyrimidinium perchlorates were obtained by the condensation of 3-amino-s-triazolo[4,3-a]pyridinium perchlorate with -diketones, -chlorovinyl ketones, -chlorovinyl aldehydes, and 1,1,3,3-tetraethoxypropane. Unsymmetrical -diketones, -chlorovinyl ketones, and -chlorovinyl aldehydes in this reaction give mixtures of isomeric products that differ with respect to the position of the substituents in the pyrimidine ring. The structures of the reaction products and their ratios in the reaction mixture were determined by means of the PMR spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1433–1435, October, 1971     

Inside Cover: General Reductive Amination of Aldehydes and Ketones with Amines and Nitroaromatics under H2 by Recyclable Iridium Catalysts (Chin. J. Chem. 9/2017)

The inside cover picture shows secondary and tertiary amines, which are important intermediates in organic synthesis for the preparation of natural products, pharmaceutical and agronomical compounds. The direct reductive amination of aldehydes and ketones represents a powerful tool for the preparation of secondary and tertiary amines. Here, direct and general reductive amination of aldehydes and ketones with amines and nitroaromatics was presented under H₂ using recyclable iridium catalysts, and lots of secondary and tertiary amines were produced in high yields. Moreover, the heterogeneous iridium catalysts Ir@NC(600‐2h) can be reused several times without evident deactivation. More details are discussed in the article by Huang et al. on page 1371–1377.

     

5-Alkoxy-2-vinyloxazolidines

2-Methyl-1-arylsulfonylaziridines, formed in the reaction of tosyl and p-nitrobenzenesulfonyl azides with methyl vinyl ether, react regiospecifically with ,-unsaturated aldehydes and ketones to give 5-methoxy-2-vinyl-3-arylsulfonyloxazolidines. The effect of the structure of the aziridines and unsaturated aldehydes and ketones on the stereoselectivity of their reactions is discussed.Communication VII of the series Reaction of organic azides with unsaturated compounds. See [1] for communication VI. The results of this research are protected by an author's certificate [2].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 332–336, March, 1977.     

Ruthenium(ii)-catalyzed regioselective 1,6-conjugate addition of umpolung aldehydes as carbanion equivalents

One of the most efficient and reliable approaches to construct C–C bonds involves the conjugate addition of carbon nucleophiles to electron-deficient ketones. Yet, 1,6-conjugate additions of extended conjugated systems largely remain underexplored due to difficulties in controlling the regioselectivity. Herein, we report umpolung aldehydes as carbanion equivalents for highly regioselective 1,6-conjugate addition reactions to unsaturated ketones, with preliminary studies of the enantioselective variant. The synergy of ruthenium(ii) catalyst and electron-rich, bidentate phosphine ligand is essential for the reactivity and selectivity under mild reaction conditions.

Highly regioselective 1,6-conjugate addition was developed using hydrazone as carbanion equivalent catalyzed by ruthenium under mild conditions.     

Investigations of polyhydroacridines and related compounds

A method is proposed for the synthesis of polyhydroacridines with a hydroxyl group in the side chain by condensation of 4-lithio-sym-octahydroacridine and 4-lithio-1,2,3,4-tetrahydroacridine with aldehydes and ketones. The dehydration of the compounds obtained was studied. 4,5-Diarylidineoctahydroacridines are formed by heating 4--hydroxybenzylsym-octahydroacridine in acetic anhydride in the presence of aromatic aldehydes.See [1] for Communication VI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1542–1545, November, 1970.     

Paterno-Buchi photocyclization of 2-siloxyfurans and carbonyl compounds. Notable substituent and carbonyl (Aldehyde vs ketone and singlet- vs triplet-excited state) effects on the regioselectivity (Double-bond selection) in the formation of bicyclic exo-oxetanes

Paterno-Buchi coupling, photochemical [2 + 2] cycloaddition, of carbonyl compounds 2a-f with 2-siloxyfurans 1a-d has been investigated in detail. The stereoselective formations of exo-oxetanes 3 and 4 were observed in high yields. The regioselectivity (double-bond selection, 3 vs 4) was found to be largely dependent upon the carbonyls, the substituents at the furan ring, and the excited state of the carbonyls (singlet vs triplet). The photoreaction of aldehydes 2a-c gave bicyclic exo-oxetanes 3 and 4 at regio-random, independent upon their excited states and the substituents at furan ring. However, the photoreaction of the triplet state of ketones 2d-f was found to give regioselectively exo-oxetanes 4, except for the 4-methyl-2-siloxyfurane 1d case. The singlet-excited state of acetone 2f gave both oxetanes 3 and 4 at regio-random. For the singlet-state photochemistry, the approach direction of the electrophilic oxygen of the excited carbonyls to the furan ring is proposed to be an important factor for the exo-stereoselection. The Griesbeck model can rationalize the regio- and exo-selective formation of oxetanes in the triplet-state photoreaction.     

Synthesis and spectral-luminescence properties of hetarylethylene derivatives of 2,5-diphenyloxazole and 2,5-diphenyl-1,3,4-oxadiazole

A number of new organic luminophores was synthesized by PO olefination from 2- (4-bromomethylphenyl)-5-phenyloxazole and -1,3,4-oxadiazole and various heterocyclic aldehydes that contain a furan ring. The absorption and fluorescence spectra of the products in toluene, as well as their scintillation characteristics, were measured. The effect of the electronic nature of the substituents on the spectral-luminescence properties of the luminophores is discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 617–621, May, 1982.     

Alkylation of furan by olefins

IR and Raman spectra of 17 mono- and polyalkyl furans, with alkyl groups in various positions in the furan ring, are investigated. A change in Raman spectrum is found for C-H bond valence vibrations when alkyl groups substitute the furan ring at the position. Characteristic frequencies are found for 2-substituted and 2, 5-disubstituted furans.For part VI see [6].     

Asymmetric transfer hydrogenation of acetophenone derivatives with novel chiral phosphinite based η-p-cymene/ruthenium(II) catalysts

Enantioselective reduction of prochiral ketones to optically active secondary alcohols is an important subject in synthetic organic chemistry because the resulting chiral alcohols are extremely useful, biologically active compounds. The new chiral ligands (2R)-2-[benzyl{(2-((diphenylphosphanyl)oxy)ethyl)}amino]butyldiphenylphosphinite, 1 and (2R)-2-[benzyl{(2-((dicyclohexylphosphanyl)oxy)ethyl)}amino]butyldicyclohexylphosphinite, 2 and the corresponding ruthenium(II) complexes 3 and 4 have been prepared. The structures of these complexes have been elucidated by a combination of multinuclear NMR spectroscopy, IR spectroscopy and elemental analysis. ³¹P-{¹H} NMR, DEPT, ¹H-¹³C HETCOR or ¹H-¹H COSY correlation experiments were used to confirm the spectral assignments. These ruthenium(II)-phosphinite complexes have been used as catalysts for the asymmetric transfer hydrogenation of acetophenone derivatives. Under optimized conditions, aromatic ketones were reduced in good conversions and in moderate to good enantioselectivities (up to 85% ee).     

DFT-assisted design and evaluation of bifunctional copper(I) catalysts for the direct intermolecular addition of aldehydes and ketones to alkynes

Bifunctional catalysts containing discrete metal pi-acid and amine sites were designed and investigated for the direct intermolecular addition of aldehydes and ketones to unactivated alkynes. Copper(I)-based catalysts were prioritized based on intramolecular (Conia-ene type) reactions, and complexes were designed with tridentate ligands and potentially hemilabile heterocyclic spacers. The structures of the designed catalysts were computed using density functional theory (DFT), and the relative energies of putative catalytic intermediates were estimated and used to prioritize catalyst designs. Novel bifunctional precatalysts containing a thiazole spacer were synthesized via a 9-step sequence and combined with transition metals before screening for the direct addition of aldehydes and ketones to several internal and terminal alkynes. Despite the lack of desired intermolecular reactions, DFT calculations of putative catalyst intermediates appears to be a promising strategy for the design and prioritization of bifunctional catalysts for CC bond formation.