Catalytic synthesis of dihydrofurans (review)

Various methods for the preparation of 2,3-dihydrofuran, 2,5-dihydrofuran, 2-methylenetetrahydrofuran, and their alkyl and aryl derivatives are examined. The most promising method for the preparation of 2,3-dihydrofuran is the conversion of 1,4-butanediol on cobalt catalysts. 2,5-Dihydrofuran is obtained by dehydration of 2-butene-1,4-diol on Al₂O₃, cobalt-containing and other catalysts, while 2-methylenetetrahydrofuran is obtained by dehydrohalogenation of tetrahydrofurfuryl halides. The various methods for the isomerization of 2,5-dihydrofuran to 2,3-dihydrofuran are discussed. Examples of the application of dihydrofurans in organic synthesis are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1299–1311, October, 1982.     

Transformations of heterocyclic compounds on membrane catalysts

The transformations of furan, -methylfuran, furfural, and 2,3-dihydrofuran on a palladium — nickel membrane catalyst at 50–300°C under conditions of diffusion of hydrogen through the catalyst were investigated. Under these conditions furan is hydrogenated to tetrahydrofuran in quantitative yield. Considerable amounts of furan, the hydrogenation of which in the presence of the above-named derivatives is inhibited, are detected in the catalyzate along with hydrogenation products in the transformations of -methylfuran, furfural, and 2,3-dihydrofuran.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 599–601, May, 1975.     

Liquid-phase hydroformylation of 2,3- and 2,5-dihydrofurans

The synthesis of 3-formyl derivatives of the tetrahydrofuran series was carried out by hydroformylation of 2,3-dihydrofuran and 2,5-dimethoxy-2,5-dihydrofuran in the presence of HRh(CO)(PPh₃)₃. The influence of the temperature, pressure, catalyst concentration, and the nature of the solvent on the conversion of dihydrofuran, the composition of aldehydes obtained and the selectivity of their formation was investigated.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2569–2571, November, 1989.     

Thermal reactions of dihydrofurans

Summary In contact with active birch charcoal at 470–480° in a stream of nitrogen 2-n-propyl-4,5-dihydrofuran isomerized to propylcyclopropylketone, whereas 2-n-butyl-2,5-dihydrofuran was dehydrogenated to -butylfuran under the same conditions.     

Synthesis of Perfluoro- and 2-Trifluoromethylpentafluorodihydrofurans and Their Epoxy Derivatives

Perfluorotetrahydrofuran-2-carboxylic acid was converted through a series of transformations into perfluoro-2,3-dihydrofuran and perfluoro-2,5-dihydrofuran; likewise, from (2-perfluorotetrahydrofuryl)difluoroacetic acid 2-trifluoromethylpentafluoro-2,3-dihydrofuran was obtained. Perfluoro-2,3-dihydrofuran and 2-trifluoromethylpentafluoro-2,3-dihydrofuran underwent isomerization into perfluoro-2,5-dihydrofuran and 2-trifluoromethylpentafluoro-2,5-dihydrofuran by the action of cesium fluoride. Treatment of perfluoro-2,5-dihydrofuran with SbF₅ resulted in ring opening and formation of cis-perfluoro-2-butenoyl fluoride, while 2-trifluoromethylpentafluoro-2,3-dihydrofuran was converted into 2-trifluoromethylpentafluoro-2,5-dihydrofuran under the same conditions. Perfluoro-3,4-epoxytetrahydrofuran and 2-trifluoromethyl-3,4-epoxypentafluorotetrahydrofuran containing fused oxirane and tetrahydrofuran rings were synthesized by reactions of perfluoro-2,5-dihydrofuran and 2-trifluoromethylpentafluoro-2,5-dihydrofuran, respectively, with sodium hypochlorite.     

Heterocyclization of 1-acetoxy-4-halo-substituted 2-butenes in the presence of alkali

The reaction of 1-acetoxy-4-halo-substituted 2-butenes with potassium hydroxide was studied. It was established that trans-1,4-haloacetates form -oxides of 1,3-dienes, whereas the corresponding cis isomers form 2,5-dihydrofuran derivatives. It was observed that the acetyl group in these compounds facilitates, as compared with halovinylhydrins, the formation of the corresponding heterocycles under the conditions described.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10. pp. 1317–1319, October, 1988.     

Research on lactams

The reaction of O-phenylhydroxylamine hydrochloride with -oxocaprolactam gave -oxocaprolactam O-phenyloxime, which gave two substances -1,2,3,4-tetrahydro-pyrido[2,3-c]coumarin as the principal product and 1-oxo-10a-hydroxy-1H-2,3,4,5, 5a,10a-hexahydrobenzofuro[2,3-c]azepine as the minor product — under the conditions of the Fischer reaction. The minor product was converted to 1-oxo-1H-2,3, 4,5-tetrahydrobenzofuro[2,3-c]azepine in quantitative yield by dehydration in trifluoroacetic acid.See [1] for communication XXXI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1504–1507, November, 1978.     

Low-molecular-weight bioregulators 4. Synthesis of 2-isopropyl-2,5-dimethyl-2,3-dihydrofuran — The sex pheromone of the leather-winged sailorHylecoetus Dermestoides L.

A new four-stage method has been developed for obtaining racemic 2-isopropyl-2,5-dimethyl-2,3-dihydrofuran — the sex pheromone of the leather-winged sailorHylecoetus Dermestoides L.For Communication 3, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 468–471, April, 1992.     

Cyclization of N-alkylazinium cations with bisnucleophiles. 6. Cycloelimination of tetrahydro-endo-furo[2,3-b]quinoxalines leading to 2,3-disubstituted tetrahydroquinoxalines

The reaction of an N-methylquinoxalinium salt with a -diketone under thermodynamic-control conditions leads to 2,3-disubstituted tetrahydroquinoxaline via cycloelimination of the initially formed tetrahydro-endo-furo[2,3-b]quinoxaline.See [1] for communication 5.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1410–1416, October, 1982.     

An Ab Initio Study of the Relative Stabilities and Molecular Structures of 3-Substituted 2,5-Dihydrofurans and 4-Substituted 2,3-Dihydrofurans

The geometry optimized structures and total energies of 3-substituted (R) 2,5-dihydrofurans (a) and their isomers, 4-substituted 2,3-dihydrofurans (b), have been determined by ab initio calculations at the MP2/6-31G^*//HF/6-31G^* level. The nature of the moiety R has a marked effect on the relative total energies of the isomeric forms: at the calculation level cited, the reaction enthalpies for the a b isomerization range from +4.7 kJ mol^–1 for R = MeO to –30.5 kJ mol^–1 for both R = COOMe and R = NO₂. The reaction enthalpies appear to be controlled by the electronic effect of R on the strength of p- conjugation in b. The a isomer has a planar ring, independent of R (excluding NH₂), whereas the planarity of b depends on the electronic nature of R: the 2,3-dihydrofuran ring is planar for both R = COOMe and R = NO₂, but nonplanar for less conjugation-enhancing substituents.     

Behavior of an alkylthioacetaldehyde under conditions of the Mannich reaction

Conclusions Alkylthioacetaldehydes under the conditions of the aminomethylation reaction give-alkylthioacro-leins, which under the synthesis conditions are dimerized to 2-formyl-2,5-dialkylthio-2,3-dihydro--pyrans.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2516–2519, November, 1972.     

Highly diastereoselective synthesis of new chromenylaminoanthraquinones through a one-pot, three-component hetero Diels–Alder reaction

A new, efficient, and diastereoselective one-pot synthesis of cis-fused pyrano and furano chromenylaminoanthraquinones through hetero Diels–Alder reaction of 1-aminoanthraquinone and salicylaldehydes with electron-rich alkenes such as 3,4-dihydro-2H-pyran, 2,3-dihydrofuran, and ethyl vinyl ether under mild conditions is reported.     

Condensed isoquinolines. 9. Alkylation of 7,12-dihydro-5H-isoquino[2,3-a]quinazolin-5-ones

The alkylation of 7,12-dihydro-5H-isoquino[2,3-a]quinazolin-5-one proceeds at N₍₆₎ or C_(–) depending on the type of alkylating agent and reaction conditions. C_(–)-Alkylation occurs in the presence of base. The secondary alkylation of the 7-alkyl derivatives occurs at the same position under these conditions. Depending on the conditions, the reaction with o-xylylene dibromide leads to spiro[5H-isoquino[2,3-a]quinazolin-7(12H).2-indane]-5-one or 11-oxo-4b,5,10,16-tetrahydro-11H-10a-azonia-15b-azadibenz[a,e]pleiadene bromide, which are derivatives of new heterocyclic systems.Communication 8, see ref. [1].See also Letter to Editor [2].Taras Shevchenko Kiev University, 252017 Kiev, Ukraine. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 643–652, May, 2000.     

Direct spectrophotometric method for the determination of cobalt with indane 1,2,3-trionetrioxime in aqueous medium

A simple, sensitive and selective Spectrophotometric method has been developed for the determination of cobalt using indane 1,2,3-trionetrioxime (ITT): The method is based on the colour reaction between ITT and cobalt(II) in sodium acetate-acetic acid buffer (pH 4.5–7.5) medium. The calibration graph for measurement at 320 nm is linear in the range 1.18–23.60g of cobalt per 25 ml, with molar absorptivity of 5.32×10⁴1mol^–1 cm^–1. The effect of interfering ions has been studied and the method was applied to the determination of cobalt in alloys, with good results.     

Dichloromethyl tert-butyl ketone in the Darzens reaction

The condensation of dichloromethyl tert-butyl ketone (1) with benzaldehyde, para-bromobenzaldehyde, and 2,4-dichlorobenzaldehyde under conditions for the Darzens reaction gives 1-aryl-1-chloro-4,4-dimethyl-2,3-pentanediones (2–4). In the case of nitrobenzaldehydes, the reaction products are 1-aryl-2-chloro-1,2-epoxy-4,4-dimethylpentanones (5 and 6), which isomerize to -chloroketones (7 and 8) upon prolonged storage or heating at reflux in benzene.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Science Center, Russian Academy of Sciences, 420083 Kazan. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 438–441, February, 1992.     

Chemical modification of estafiatin

A high reactivity of the olefinic double bonds of the lignin (Lg) macromolecule in the reaction with molecular chlorine has been found which has permitted the chlorination of Lg to be carried out under cryogenic conditions at 150–250 K. The process takes place by a radical-chain mechanism with a length of the kinetic chain of approximately 1000 units. The bulk of the chlorine is consumed in the olefinic chains of the Lg. Other reaction products besides chlorolignin are hydrogen chloride and phenoxyl radicals, which have singlet ESR spectrum (H=1.0–1.2 mT) and are retained in the chlorinated samples of Lg to 250 K.Institute of Chemical Physics, Academy of Sciences of the USSR, Chernogolovka, Moscow Province. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 671–676, September–October, 1990.     

Synthesis of pyrroloquinolines

The ethyl ester of -(2,3-dimethylindolyl-5)aminocrotonic acid under Vilsmeier reaction conditions is converted into isomeric linear and bent pyrroloquinolines with predominant formation of the latter. The enaminoketone which is obtained from the same aminoindole and dibenzoylmethane under the same conditions underoges the usual Comb cyclization with a change in the ratio for the yield of isomeric pyrroloquinolines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 228–230, February, 1989.     

Synthesis and carbene decomposition of functionally substituted diazoacetate esters. 6. Propargyl diazoacetate

A synthesis of propargyl diazoacetate (I) was carried out and its chemical transformations were studied. The reaction of (I) in the presence of Rh(OAc)₂ at 25C with 1-pentyne gives the propargyl ester of l-propylcyclopropene-3-carboxylic acid in 80% yield, while reaction with 2,3-dimethyl-2-butene at 60C results in the propargyl ester of tetramethylcyclopropanecarboxylic acid in 10% yield. Compound (I) reacts under the same conditions (35–60C) with ether, CH₂Cl₂ and water, with the formation of propargyl esters of ethoxyacetic, 2,3-dichloropropionic, and a mixture of glycols and 2-[(propyn-2-yl)-oxycarbonyl]methoxy acetic acids in yields of up to 35%. A spontaneous oligomerization of (I) was observed as a result of a dipolar [1, 3]-cycloaddition of the CH=N₂ fragment of one molecule of (I) to the terminal triple bond of the second molecule with the formation of oligomers of 3-hydroxymethylpyrazole-5-carboxylic acid.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1051–1056, May, 1991.     

A study of the use of crystalline titania for cobalt fixation

A study of fixation of cobalt on the crystalline matrix of titania by co-precipitation was carried out. The tracer level solid-liquid distribution of⁶⁰Co over preformed hydrous titania showed an appreciable uptake of 71%. Macro amounts of Co²⁺ ions were precipitated along with Ti(IV) hydroxide (pH 8–9) and a maximum loading of 29 wt% was observed. The Soxhlet leachabilities of the calcined mixed mass, heated at 1000 °C, were found to be in the order of 10^–1 g·m^–2·d^–1 and the observation of structural changes of the original host matrix of titania revealed the fixation of cobalt in the mineral assemblage of CoTiO₃ (rhombohedral) and the rutile form of titania.     

Electrochemical ω-epoxidation of the ethyl ester of Z,Z-farnesylic acid

Conclusions The anodic -epoxidation of the ethyl ester of Z,Z-farnesylic acid proceeds regioselectively when the electrolysis is carried out under rigorously controlled conditions with I=10–12 mA and V=2–2.5 V.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 224–225, January, 1985.The authors thank V. P. Gul'tyai for assistance in carrying out the electrochemical experiments and for a discussion of the results.