A mild method for the synthesis of bis-pyrazolo[3,4-b:4′,3′-e]pyridine derivatives

A mild and efficient method for the synthesis of bispyrazolo[3,4-b:4′,3′-e]pyridines from 5-aminopyrazoles and aromatic aldehydes using an inexpensive FeCl₃ catalyst is reported. The reaction temperature was reduced from 220–250?°C to 130?°C compared to conventional methods. A large proportion of the products precipitated directly from the mixture at room temperature. Aliphatic and α,β-unsaturated aldehydes selectively resulted in formation of the corresponding 1H-pyrazolo[3,4-b]pyridine derivatives. A possible domino reaction mechanism was also proposed. Several aryl alkynyl groups were introduced to these tricyclic molecules via the Sonogashira coupling reaction.     

Some reactions of tetrafluoroethylene oligomers

As part of a programme to prepare and evaluate a series of perfluoro- chemicals for use as inert fluids, the fluorinations of some tetrafluoroethylene oligomers over cobalt (III) fluoride have been studied.Fluorination of perfluoro-3,4-dimethylhex-3-ene (tetramer) and perfluoro-4-ethyl-3,4-dimethylhex-2-ene (pentamer) over CoF₃ at 230°C and l45°C respectively afforded the corresponding saturated fluorocarbons however, at 250°C, pentamer gave predominantly the saturated tetramer. The thermal behaviour of these saturated fluorocarbons alone and in the presence of bromine and toluene has been studied.Pyrolysis of pentamer over glass beads at 500°C gave perfluoro-1,2,3- trimethylcyclobutene and isomers of perfluoro-2,3-dimethylpenta-1,3- diene. Under similar conditions perfluoro-2-(1-ethyl-1-methylpropyl). 3-methylpent-1-ene (hexamer) gave perfluoro-1-methyl-2-(1-methyl- propyl)-cyclobut-1-ene and perfluoro-2-methyl-3-(1-methylpropyl)-buta- 1,3-diene.These reactions and the structural elucidation of the products will be discussed.     

Fluorocyclohexanes. Part XVII. Dehydrofluorinations of the cis and the trans isomers of 2H-1-(difluoromethyl)decafluorocyclohexane

2H-1-(Difluoromethyl)octafluorocyclohex-1-ene (I) and cobalt trifluoride at 165 °C afforded 2H-1-(trifluoromethyl)octafluorocyclohex-1-ene (IV) and four decafluorocyclohexane derivatives: the cis (III), and trans (V), -2H-1-(trifluoromethyl)-; the cis (VII), and trans (VI), 2H-1-(difluoromethyl) compounds. Dehydrofluorination of VII, using aqueous potassium hydroxide, gave only one alkene, 1-(difluoromethyl)nonafluorocyclohex-1-ene (VIII). In a slower reaction VI afforded two alkenes, mainly VIII, But also an isomer, 1-(difluoromethyl)nonafluorocyclohex-2-ene (IX) (ratio 2:1).     

Effect of the chalcogen nature on the reaction of propane-1,3-dichalcogenolates with 2,3-dichloroprop-1-ene

The direction of the reaction of propane-1,3-dichalcogenolates with 2,3-dichloroprop-1-ene in the system hydrazine hydrate-KOH depends not only on the conditions but to a greater extent on the chalcogen nature. Dipotassium propane-1,3-dithiolate and propane-1,3-diselenolate give rise to products of substitution of the chlorine atom on the sp ³-carbon atom, which are capable of undergoing further transformations (domino reaction). Dipotassium propane-1,3-ditellurolate promotes elimination of both chlorine atoms with formation of allene.     

Tandem Prins cyclization for the synthesis of 1,8-dioxa-3-azaspiro[4.5]dec-2-ene derivatives

A tandem Prins strategy has been developed for the synthesis of 1,8-dioxa 3-azaspiro[4.5]dec-2-ene derivatives using 5?mol% Cu(OTf)₂ in dichloromethane at 0?°C under mild reaction conditions in short reaction times. This method provides the products in good yields with a diverse substitution pattern.     

Synthesis of new indolylpyrrole derivatives via a four-component domino reaction between arylglyoxals,acetylacetone, indole and aliphatic amines in aqueous media

A novel synthesis of indolylpyrrole derivatives is described by a four-component domino reaction between arylglyoxals, acetylacetone, indole and aliphatic amines in water as solvent at 60?°C without using any catalyst or promoter. The FT-IR, ¹H NMR, ¹³C NMR spectral and elemental analysis confirm the structures of the products.     

Low pressure,highly active rhodium catalyst for the homogeneous hydroformylation of olefins

Hex-1-ene hydroformylation was examined at pressures of 1–11 atm and 40 °C, using Rh(acac)[P(OPh)₃]₂ + P(OPh)₃ as catalyst. The highest efficiency of aldehydes was achieved employing a small P(OPh₃)₃ excess-[P(OPh)₃]:[Rh] = 2:1. For reactions carried out at 1 atm, very high n/iso ratios i.e. 10–80 were obtained. Pressure increase caused a systematic drop of the n/iso ratio to ca. 5 at 11 atm. Simultaneously with hydroformylation, isomerisation of hex-1-ene to hex-2-ene occurs, but the contribution of the latter declines with increasing pressure. IR examination of the reaction mixture revealed that HRh(CO)[P(OPh)₃]₃ was the active form of the catalyst.The same catalytic system was applied in propylene hydroformylation at 5–10 atm pressure and 40 °C. In such conditions the yield of aldehydes was 10–70%, with a n/iso selectivity of 2–10.     

Direct sulfenylation of acetone with benzothiazolesulfenamides to benzothiazolylthio-substituted alkylaminopropene: synthesis and application

N-Substituted derivatives of 2-benzothiazolesulfenamides give high yields of 1-(2′-benzothiazolylthio)-2-alkylaminoprop-1-ene and 1,1-bis-(2′-benzothiazolylthio)-2-alkylaminoprop-1-ene in a reaction with acetone in the temperature range from 56°C to 70°C and in the presence of a small amount of water. The α-sulfenylated carbonyl product, 2′-benzothiazolylthiopropan-2-one, is supposed to be an intermediate of this one-pot synthesis. 1,1-Bis-(2′-benzothiazolylthio)-2-tert-butylaminoprop-1-ene has been proved an accelerator of sulfur curing of rubber composites with high processing safety.     

Efficient Synthesis of 3‐Phenylnaphtho[2,3‐b]furan‐4,9‐diones in Water and Their Fluorimetric Study in Solutions

A simple and efficient protocol has been developed for the synthesis of 3‐phenylnaphtho[2,3‐b]furan‐4,9‐diones by domino reaction of α‐bromonitroalkenes to 2‐hydroxynaphthalene‐1,4‐dione. With the optimal reaction conditions [NaOAc (120 mol%), water, 70°C, 7 h], the scope of the domino reaction was explored and the green approach provided the desired products in moderate to good yields at elevated temperature under aqueous‐mediated conditions. A mechanistic rationalization for this reaction is also provided. The absorption characteristics of the compounds were examined by UV‐Vis spectra and fluorescence spectroscopy. All compounds were fluorescent in solution emitting at blue light (432–433 nm), green light (512–536 nm), or yellow light (591 nm).     

Stereochemistry of an Ene Reaction Involving 1,7-Dienes; Bicyclo[3.3.1]nonanes from (3-Cyclohexenyl)diallylcarbinols

(3-Cyclohexenyl)diallylcarbinols undergo a thermal retro-ene reaction to give crotonylcyclohexenes at ca. 200°. A side-reaction is an ene reaction to give bicyclo[3.3.1]nonanes. These become the main products above 300°. The stereochemistry of 2-allyl-1,4,6-trimethylbicyclo[3.3.1]-6-none-2-ols and related compounds is discussed, and a case is described in which the allyl group is not freely rotating.     

Addition von organomagnesium-verbindungen an nicht aktivierte CC-doppelbindungen : IV. Benzylmagnesiumchlorid und olefine

Benzylmagnesium chloride (I) adds to ethylene and 1-alkenes, to the strained CC double bonds in bicyclo[2.2.1]hept-2-ene and bicyclo[2.2.1]heptadiene and to 1,3-alkadienes if the reaction of the etherate of (I) with olefin is carried out in an apolar reaction medium between 60 and 130°. Reaction products of the mono-olefins are the 1,1-adducts; derivatives of divinylcyclohexane are formed with butadiene as 1,3-adducts. With bicyclo[2.2.1]heptadiene the addition of the magnesium compound is followed by an intramolecular MgC-addition to the second double bond forming 2-benzyltricyclo[2.2.1.0¹]hept-3-ylmagnesium chloride.     

Synthesis of 7-sulfonyl-substituted norpinan-6-ones and -thiones from 1-bromotricyclo[4.1.0.0<Superscript>2,7</Superscript>]heptane

1-Bromotricyclo[4.1.0.0^2,7]heptane reacted with benzene- and methanesulfonyl thiocyanates in benzene at 20°C via anti addition to the central C¹–C⁷ bicyclobutane bond with formation of 6-endo-bromo-6-exo-thiocyanato-7-syn-(R-sulfonyl)bicyclo[3.1.1]heptanes. Treatment of the benzenesulfonyl thiocyanate adduct with potassium tert-butoxide in THF at 20°C gave 7-endo-(benzenesulfonyl)norpinan-6-one, whereas the reaction with 1,8-diazabicyclo[5.4.0]undec-7-ene in methylene chloride afforded 7-exo-(benzenesulfonyl)-norpinane-6-thione which was converted into 7-exo-(benzenesulfonyl)norpinan-6-one by alkaline hydrolysis.     

Flow pyrolysis of hexafluorodisilane as a source of highly reactive difluorosilylene

Gas-phase fast-flow pyrolysis of Si₂F₆ at 670–720°C in a mixture with excess 1,3-butadiene led to the formation of high yields (56–75%) of 1,1-difluro-1-silacyclopent-3-ene. A lower limit of k₂ = 10⁶ M⁻¹ s⁻¹ for the gas-phase addition of SiF₂ to butadiene at 700°C was estimated.     

A New Strategy for Enantioselective Construction of Multisubstituted Five‐Membered Oxygen Heterocycles via a Domino Michael/Hemiketalization Reaction

A new highly enantioselective domino Michael/hemiketalization reaction of α‐hydroxyacetophenone with β,γ‐unsaturated α‐keto esters for the synthesis of 2,2,4,5‐tetrasubstituted chiral tetrahydrofurans is reported. With 2 mol % intramolecular dinuclear zinc‐AzePhenol complex prepared in situ from the reaction of multidentate semi‐azacrown ether ligand with ZnEt₂, the corresponding anti‐multisubstituted tetrahydrofuran products were obtained in up to 90 % yields, and 98 % enantiomeric excess (ee) at 0 °C for 45 min. Moreover, the products were easily converted to 2,3,5‐trisubstituted 2,3‐dihydrofurans without any loss in optical activity.     

Convenient synthesis of ethylene carbonates from carbon dioxide and 1,2-diols at atmospheric pressure of carbon dioxide

An efficient and convenient synthesis of ethylene carbonates was achieved by the reaction of carbon dioxide with 1,2-diols in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), followed by treatment with 1-bromobutane. This DBU-promoted transformation proceeded at an atmospheric pressure of carbon dioxide at 25 °C and gave ethylene carbonates in good yields.     

The thermal decomposition of (NH4)4V2O11 in a nitrogen atmosphere and the kinetics of the first decomposition step

Although the reaction products are unstable at the reaction temperatures, at a heating rate of 2 deg·min^?1 ammonium peroxo vanadate, (NH₄)₄V₂O₁₁, decomposes to (NH₄)[VO (O₂)₂ (NH₃)] (above 93°C); this in turn decomposes to (NH₄) [VO₃ (NH₃)] (above 106°C) and then to ammonium metavanadate (above 145°C). On further heating vanadium pentoxide is formed above 320°C. The first decomposition reaction occurs in a single step and the Avrami-Erofeev equation withn=2 fits the decomposition data best. An activation energy of 148.8 kJ·mol^?1 and a ln(A) value of 42.2 are calculated for this reaction by the isothermal analysis method. An average value of 144 kJ·mol^?1 is calculated for the first decomposition reaction using the dynamic heating data and the transformation-degree dependence of temperature at different heating rates.     

Lipase-catalyzed domino Michael–aldol reaction of 2-methyl-1,3-cycloalkanedione and methyl vinyl ketone for the synthesis of bicyclic compounds

Synthesis of bicyclic compounds was achieved via a lipase-catalyzed, stereoselective, domino Michael–aldol reaction of 2-methyl-1,3-cycloalkanedione and methyl vinyl ketone. Appropriate reaction conditions, including the type of enzyme, solvent, and temperature, were determined. In addition, the effects of solvent polarity and addtives were investigated. The reaction proceeded in the presence of lipase AS in a solution of 20% acetone in dimethylsulfoxide (DMSO) at 10 °C for 8 days, followed by the addition of p-toluenesulfonic acid (TsOH) to afford bicyclic compounds in 51–83% yields with moderate stereoselectivity. Although this domino Michael–aldol reaction showed only moderate stereoselectivity, even with the acid-supported enhancement of the reaction, these results represent potential new applications for lipase.     

Polyfluoro-compounds based on the cycloheptane ring system. Part 6. Bicyclic compounds derived from nonafluorocyclohepta-1, 3-dienes and from octafluorocyclohepta-1, 3, 5-triene

1H-, 2H-, and 5H- Nonafluoro- and 1H,4H-octafluoro-cyclohepta-1,3 diene afforded the corresponding H-substituted polyfluorobicyclo(3, 2, 0)- hept-6-enes by cross-ring bond formation between positions 1 and 4. Octafluorocyclohepta-1, 3, 5-triene similarly gave octafluorobicyclo- (3,2,0)hepta-2,6-diene. By passage over cobalt(III) fluoride at 100°C, the 1H-bicyclo-6-ene gave 1H-undecafluorobicyclo(3, 2, 0)heptane and thence the corresponding fluorocarbon. The bridgehead hydrogen of the 1H- bicyclo-ane was sufficiently acidic to exchange for deuterium with deuterium oxide, alone or containing some potassium hydroxide, but longer exposure to aqueous potash gave decafluorobicyclo(3, 2, 0)hept-1(5)-ene. This was oxidised by potassium permanganate in acetone to give decafluoro-1, 5- dihydroxy-8-oxabicyclo(3, 2, 1)octane (hydrated), which underwent methylation by diazomethane to the corresponding 1,5-dimethoxy-compound. A Diels-Alder reaction between ethylene and 1H-nonafluorocyclohepta-1, 3- diene afforded 1H,8H,8H,9H,9H-nonafluoro-bicyclo(3,2,2)non-6-ene. Cobalt (III) fluoride at 300°C converted this principally to 1H-pentadecafluoro- bicyclo(3,2,2)nonane. The bridgehead hydrogen of this was exchanged for deuterium using deuterium oxide alone or containing potassium hydroxide. However, dehydrofluorination occurred with bases, though an olefin could not be isolated.     

Separation and characterization of products from thermal cracking of individual and mixed polyalkenes

Low-density polyethylene (LDPE), polypropylene (PP), and their mixture in the mass ratio of 1: 1 (LDPE/PP) were thermally decomposed in a batch reactor at 450°C. The formed gaseous and oil/wax products were separated and analyzed by gas chromatography. The oils/waxes underwent both atmospheric and vacuum distillation. Densities, molar masses and bromine numbers of liquid distillates and distillation residues were determined. The first distillate fraction from the thermally decomposed LDPE contained mostly linear alkanes and alk-1-enes ranging from C₆ to C₁₃ (boiling point up to 180°C). The second distillate fraction was composed mostly of hydrocarbons C₁₁ to C₂₂ (boiling point up to 330°C). 2,4-Dimethylhept-1-ene was the major component of the first distillate fraction obtained from the product of PP decomposition, while in the 2nd distillate fraction it was 2,4,6,8-tetramethylundec-1-ene. The yields of some gaseous or liquid hydrocarbons obtained by distillation from thermally degraded LDPE/PP differed from the values corresponding to the decomposition of individual plastics due to the mutual influence of polyalkenes during their thermal cracking. Similarly, the yields of propene and methylpropene in the gaseous phase were higher in the case of mixture. Whereas the content of C₉ to C₁₇ alkanes and alkenes in the distillates separated from the liquid mixture obtained by the decomposition of LDPE/PP decreased, the formation of 2,4,6,8,10,12-hexamethylpentadec-1-ene remained unchanged. The corresponding mechanisms of thermal cracking were discussed.     

Fluorinations with potassium tetrafluorocobaltate [III]. Part VIII fluorinations of toluene and of phenylacetic acid

At 340 °C, toluene gave five 1-trifluoromethyl-substituted compounds:- -2H,4H,5H-tetrafluorocyclohexa-1,4-diene (IX); -2H-4H/5H-hexafluorocyclohex-1-ene (X); -2H-octafluorocyclohex-1-ene (IV); -nonafluorocyclohex-1-ene (III); also perfluoromethylcyclohexane (II); traces of perfluorocyclohexane (I) were found. The 1-difluoromethyl-substituted analogues of these five were also obtained:- compounds XII, XV, VIII, VI, and V, respectively. A further five 1-difluoromethyl-substituted derivatives were found:- -nonafluorocyclohex-3-ene (VII); an inseparable mixture of the -2H,4H- and -2H, 5H-heptafluorocyclohex-1-enes (XI); -2H-3H/4H-hexafluorocyclohex-1-ene (probably) (XIV); and (difluoromethyl)benzene (XIII).Structures of the unknown products were established by analysis and by nmr and ir spectroscopy. Further, the key intermediate (XII) was oxidized to difluoromalonic acid, whilst compound XV was dehydrofluorinated, to give 2H-(difluoromethyl)tetrafluorobenzene (XXI), together with an inseparable mixture of 2H,4H- and 2H,5H-1-(difluoromethyl)pentafluorocyclohexa-1,4-diene (XX). Dehydrofluorination of mixed heptafluoro-enes XI afforded 2H -1-(difluoromethyl)hexafluorocyclohexa-1,4-diene (XVIII), and mixed 2H-1- and 1H -2- (difluoromethyl)hexafluorocyclohexa-1,3-diene (XIX).Difluoromethylundecafluorocyclohexane (V) did not dehydrofluorinate.Phenylacetic acid was fluorinated likewise, and gave a similar range of products, but also one (originally an acid fluoride ?) which was converted to the methyl ester of tridecafluoro(cyclohexylacetic) acid (XVII).The probable pathway of the fluorination process could be worked out.