bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vinylpolymerisation mit reduzierenden Übergangsmetallverbindungen. VII. Polymerisation von Methylmethacrylat in Gegenwart von Molybdän(III)‐chlorid‐Sulfoxid‐Systemen
Authors: Moszner N. , Hartmann M. 
Published: December 2004

Vinyl Polymerization Initiated by Reducing Compounds of Transition Metals. VII. Polymerization of Methyl Methacrylate in the Presence of Molybdenum(III) Chloride/Sulfoxide SystemsThe polymerization of methyl methacrylate initiated by the molybdenum(III) chloride/dimethyl sulfoxide redox system was carried out at 70° in 1, 4‐dioxane. The rate of polymerization can be described by the equation Rp = k · [MoCl3]0,5 · [DMSO]0,5 · [MMA]1,0. The overall activation energy was estimated to be 36.0 kJ/mol. It was found that diethyl, dipropyl, dibutyl, diphenyl and dibenzyl sulfoxides could also initiate the polymerization of methyl methacrylate in the presence of molybdenum(III) chloride, whereas vanadium(II) chloride, vanadium(III) chloride, titanium(III) chloride and chromium(II) acetate are inactive in combination with sulfoxides.
Photochemische Reaktionen von Arylglycidethern
Authors: Timpe H.‐J. , Garcia C. , Fedtke M. 
Published: December 2004

Photochemical Reactions of Arylglycidyl EthersThe absorption, fluorescence and phosphorescence spectra, respectively, of arylglycidyl ether 1 correspond to those of other alkyl aryl ethers. Also the photolysis product distribution (λ = 254 nm) is in agreement with a normal ether photolysis. Furthermore, photoinduced epoxy ring opening takes place giving homopolyaddition oligomers and in methanolic solution also CH3OH addition products. These reactions can be explained using the model of bichromophoric molecules with the ArO‐chromophore as donor and the epoxy ring as acceptor. The calculations based on this model are in agreement with the experimental data. In the aromatic nucleus halogene substituted 1 were dehalogenated with high quantum yield (0.25 in the case of bromo substituted compound 1g). The quantum yields of the ArO‐C‐bond scission are about 0.08 independently of the aromatic ring substituents. As indicated by sensitization and quenching experiments, respectively, with aromatic hydrocarbons the photo reactions proceed via S1 state. It was found that phenol quenches the photodegradation of 1 very efficiently. Excited methyl phenyl glycerol ether 5a reacts with phenyl glycidylether 1a in its ground state producing oligomers.
Untersuchungen zur Thermischen Umsetzung von Phenylcyclopentan, ‐hexan, ‐heptan und ‐octan in der Gasphase
Authors: Lam Ho Són , Zimmermann G. , Anders G. , Bach G. , Rennecke D. , Zychlinski W. 
Published: December 2004

Studies on Thermal Conversion of Phenyleyclopentane, ‐hexane, ‐heptane, and ‐octane in the Gas PhaseThe title compounds were pyrolyzed from 700 to 780°C in a metallic laboratory tubular reactor in the presence of steam. The reaction products were analyzed by gas chromatography and by a combination of gas chromatography and mass spectrometry. From the phenylcyclanes tested, more than 65 hydrocarbons could be detected in the liquids, besides gaseous reaction products. In most cases unambiguous structures could be derived by using different analytical methods.As typical initial‐step products phenylcyclenes, ω‐phenyl‐1‐alkenes and 1‐phenyl‐1‐alkenes are formed by dehydrogenation and isomerization of the title compounds. The detection of phenylalkenes corresponds well with the isomerization of unsubstituted cyclanes to the corresponding α‐olefines described in former papers.
Reactivity of heterocyclic compounds. VI. 2,6‐Diaminopyrimidine‐5‐carbonitriles and 3,5‐Dicyanopyridones from 2‐amino‐4H‐pyran‐3, 5‐dicarbonitriles
Authors: Seoane C. , Soto J. L. , Quinteiro M. 
Published: December 2004

AbstractThe reaction of different 2‐amino‐4H‐pyrans (1, 10) with guanidine affords 2,6‐diaminopyrimidine derivatives (3). Treatment of the pyrans mentioned or their acetylated derivatives with trityl tetrafluoroborate does not yield pyrylium salts, and pyrid‐2‐one systems (8, 11, 14) are obtained from the 2‐amino‐4H‐pyrans (1, 10, 13) on treatment with H2SO4/ethanol.
Synthese, Reaktivität und 1H‐NMR‐Daten von 14,15‐Methylenderivaten der Androstan‐ und Östratrienreihe
Authors: Prousa R. , Schönecker B. , Tresselt D. , Ponsold K. 
Published: December 2004

Synthesis, Reactivity and 1H‐NMR‐Spectroscopy of 14,15‐Methylene Derivatives of the Androstane and Estratriene SeriesUnder the activating and syn‐directing effect of the 17‐hydroxy group the Simmons Smith cyclopropanation of 14,15‐unsaturated 17‐hydroxy steroids of the androstane and estratriene series 1a, 5 and 9 affords the 14,15‐methylene steroids 2a, 6 and 10 with cis position of the 14,15‐methylene and 17‐hydroxy groups in a stereospecific reaction. Oxidation of these compounds yields the 17‐keto derivatives 3, 7 and 11, which were reduced to the compounds 4a, 8 and 12 with trans position of the 14,15‐methylene and 17‐hydroxy groups by complex hydrides or diborane. In a phase transfer catalyzed reaction dichloro‐ or dibromocarbene was added to 3β, 17β‐diacetoxy‐5α‐androst‐14‐ene 1b forming the 14β, 15β‐dihalogenmethylene steroids 13 and 14. The 17‐keto steroids 7 and 11 were transformed into 17‐methyl and 17‐ethynyl derivatives 15–20. Cleavage of the cyclopropane ring of 2a, 2b and 3 by catalytic hydrogenation affords the 14β‐methyl derivatives 21–23, the acid catalyzed ring opening with hydrogen chloride yields the 14β‐chloro, 15β‐methyl derivatives 24–29. Structure elucidation has been established by 1H n.m.r. and mass spectroscopy. The configuration at C17, C14 and C15 was also determined by means of 1H n.m.r. spectroscopy, using the chemical shifts of the 18‐protons, the coupling constants and the chemical shifts of the 17‐protons. The configuration of the 17‐disubstituted steroids was established with the aid of an europium shift reagent.
Pikosekunden‐spektroskopische Untersuchungen an 1‐Phenylazo‐2‐naphtholen
Authors: Gase R. , Weber A. , Grummt U.‐W. , Epperlein J. 
Published: December 2004

Picosecond Spectroscopic Investigations of 1‐Phenylazo‐2‐naphtholsThe photoisomerization of substituted 1‐phenylazo‐2‐naphthols is studied in fluid solution and in polymer film (cellulose acetate). With the help of picosecond spectroscopy the absorption from an excited state, bleaching, and time resolved fluorescence were measured. The results can be interpreted by the assumption that during periods of less than 10 ps, the S1‐state of the azo form is changed to the S1‐state of the hydrazone form by proton transfer. This S1‐state relaxes by internal conversion and by diabatic isomerization with a time constant of 20 to 60 ps, depending on substituent and solvent. By exciting the substances solved in polymer film, we observed a relatively strong fluorescence, which is found to be amplified spontaneous emission (superfluorescence).
Synthese und Konformation einiger Dioxaspirane mit dem Bicyclo[2.2.2]octan‐System
Authors: Jamrozik Maria , Jamrozik Janusz 
Published: December 2004

Synthesis and Conformation of Some Dioxaspiranes with Bicyclo [2.2.2]octane SystemBy condensation of 7,7‐bis‐(bromomethyl)‐2,3,5,6‐dibenzo‐bicyclo[2.2.2]octane with different diols, three new “bridge‐spiranes” 1, 2 and 3 were obtained. On the basis of 1H‐n.m.r. spectra and the respective topic relations of the hydrogen atoms the dominant conformations of heterocyclic rings in these compounds have been assigned.
Darstellung und Eigenschaften hexasubstituierter Benzenderivate
Authors: Rosenthal Uwe , Schulz Wolfgang 
Published: December 2004

Preparation and Properties of Hexasubstituted BenzenesHexasubstituted benzenes are of potential interests as polypodands, host molecules and disc‐like molecules. They are prepared by catalytic cyclotrimerization of disubstituted alkynes 1–8 or by nucleophilic substitution of bromine in hexakis (bromomethyl)benzene 9–17. The different methods of preparation were compared. The new hexasubstituted benzenes were characterized by some chemical and physical properties.
Kristallin‐flüssige Heterocycloalkane. II [1]. Synthese und kristallin‐flüssiges Verhalten substituierter 1‐Phenylpiperazine
Authors: Süsse M. , Skubatz R. , Demus D. , Zaschke H. 
Published: December 2004

Liquid‐crystalline Heterocycloalkanes. II. Syntheses and Liquid‐crystalline Properties of Substituted 1‐PhenylpiperazinesSeveral homologous series of the 1,4‐disubstituted piperazines of the general formulas 4a—1, 6a—k, 7a, b, 8a—r were synthesized. Most of the new substances are liquid crystalline. Besides nematic phases also smectic phases of the types A, B and E exist, which was proved by texture and miscibility studies.Die Palette kristallin‐flüssiger Substanzen wurde in den letzten Jahren durch die Verwendung von Cyclohexan und Sechsringheterocycloalkanen als Strukturfragmente in Flüssigkristallmolekülen [2, 3] bedeutend erweitert. Diese Verbindungen besitzen meistens breite kristallin‐flüssige Existenzgebiete, niedrige Viskositätswerte und günstige dielektrische Eigenschaften. Sie sind daher gegenwärtig unentbehrliche Bestandteile der Flüssigkristallgemische in allen LCD‐Anzeigesystemen.Besonders intensiv wurden Flüssigkristalle, die den 1,3‐Dioxanring enthalten, synthetisiert und die physikalisch‐chemischen Eigenschaften untersucht [1 4–10]. Die einfache Synthese der 1,3‐Dioxane aus 2‐substituierten Propan‐1,3‐diolen und Aldehyden ermöglicht eine große Variationsbreite im Substituentenmuster. Die Untersuchungen bestätigten, daß analog den Cyclohexanderivaten nur die trans‐isomeren 1,3‐Dioxane zur Ausbildung kristallin‐flüssiger Phasen befähigt sind.
Reactions of 2‐(N‐Cyclohexyl)aminopyridine with Electrophiles
Authors: Mørkved Eva H. 
Published: December 2004

Abstract2‐(N‐Cyclohexyl)aminopyridine 1 was reported to form a 1,2‐dihydropyridine derivative with carbonyl chloride [4]. This implies that the pyridine nitrogen of 1 is a stronger nucleophile than the exocyclic nitrogen. Presently 1 is found to react with electrophiles, including carbonyl chloride, to form derivatives at the exocyclic nitrogen of 1. This is proven by relating the structures of these compounds to 2‐(N‐alkoxycarbonyl‐N‐cyclohexyl)aminopyridine 1‐oxides 5. Compounds 5 were prepared by two independent routes, thus proving the structure of 5. 1H n.m.r. and 13C n.m.r. spectra also support the assigned structures.
Über die Reaktionen von Benzimidazol‐2‐carbonsäurehydrazid mit Elektrophilen
Authors: Graubaum Heinz , Martin Dieter 
Published: December 2004

About the Reactions of Benzimidazole‐2‐carbohydrazide with Electrophilic CompoundsBenzimidazole‐2‐carbohydrazide (1) reacts with aldehydes and ketones to form N‐alkylidene‐benzimidazole‐2‐carbohydrazides(2a–j). With carbon disulfide, diphenyl carbonate and cyanates, ring closure takes place to afford 1,2,4‐triazines and 1,3,4‐oxadiazoles. Attempts to synthezise 2‐isocyanato‐benzimidazole failed.1H‐n.m.r. and 13C‐n.m.r. spectroscopic data of the compounds are given.
Zur Herstellung von Säurederivaten der Oxalsäure‐N1‐acylamidrazone
Authors: Dost J. , Stein J. , Heschel M. 
Published: December 2004

Preparation of Carboxylic Acid Derivatives of Oxalic Acid‐N1‐acyl AmidrazonesThe synthesis of oxalic acid ethylester‐N1‐acyl amidrazones 1 is described. The amidrazonecarboxylates 1 were converted to the oxalic acid‐N1‐acyl amidrazones 2 and to the corresponding carboxamides 3 and hydrazides 4, which yield [5‐amino‐1,3,4‐oxadiazol‐2‐yl]‐N1‐acylamidrazones 5.
Pyryliumverbindungen. 34 [1] 2‐Acetonyl‐2H‐thiopyrane aus 2,4,6‐Triaryl‐thiopyryliumsalzen
Authors: Zimmermann Thomas , Fischer Gerhard W. 
Published: December 2004

Pyrylium Compounds. 34. 2‐Acetonyl‐2H‐thiopyrans from 2,4,6‐Triarylthiopyrylium Salts2,4,6‐Triarylthiopyrylium salts 4 react with acetone in the presence of amine salts of weak acids (e.g. piperidine acetate) to give the hithero unknown 2‐acetonyl‐2‐H‐thiopyrans 5, the structure of which was established by spectroscopic methods. Depending on the nature of the amine salt used, the enamine 6 or the enol 7 of acetone may function as attacking nucleophile. Using the 2,4,6‐triphenyl derivative 5a as model compound, some typical reactions of 2‐acetonyl‐2H‐thiopyrans were studied. With 2,4‐dinitrophenylhydrazine, semicarbazide and thiosemicarbazide, the carbonyl derivatives 10a–c are formed. Hydrogen peroxide in acetic acid affords the S,S‐dioxide 11. Methanolic sodium methoxide or sodium hydroxide in aqueous ethanol give rise to a ring transformation yielding 1,3,5‐triphenylbenzene (12) and 2,4,6‐triphenylacetophenone (13). Under similar conditions, benzaldehyde reacts with 5a to give 2′, 4′, 6′‐triphenylchalcone (14). Perchloric acid regenerates from 5a the initial thiopyrylium perchlorate 4a.
Photochemical Reactions of Triplet Methylene Blue with arene diazonium salts relative efficiency of the oxidation and the reduction mechanisms
Authors: Becker H. G. O. , Schütz R. , Tillack B. , Rehak V. 
Published: December 2004

AbstractRate constants and efficiencies of the oxidative bleaching of triplet‐excited methylene blue by different arene diazonium salts are determined by flash photolysis and stationary experiments.In the same way the rate constants of methylene blue photoreductions by diazabicylo[2,2,2]‐octane (DABCO), sodium tetraphenyl borate (TPB), sodium ethylenediamine tetraacetate (EDTA), and allyl thiourea (ATU) are determined.According to these results TPB reduces methylene blue photochemically not exceedingly fast (ke = 1.5 × 107M−1s−1) but with a high efficiency (η = 0.8).At high diazonium salt concentrations (10−1 – 10−2 M), the oxidation and the reduction mechanisms of the triplet‐methylene‐blue sensitized dediazoniation of arene diazonium salts have similar efficiencies at high as well as at low light intensities.At low diazonium salt concentrations and with diazonium salts of low reactivity, the reduction mechanism is favoured over the oxidation mechanism.
Trennung und absolute Konfiguration der Enantiomeren von cis‐6,6a,7,8,13,13a‐Hexahydro‐1‐benzopyrano[4,3‐b]‐1,5‐ benzodiazepin‐Derivaten
Authors: Werner W. , Burckhardt G. 
Published: December 2004

Resolution and Absolute Configuration of the Enantiomers of cis‐6,6a,7,8,13,13a‐Hexahydro‐1‐benzopyrano[4,3‐b]‐1,5‐benzodiazepine DerivativesThe enantiomers of the cis‐6,6a,7,8,13,13a‐hexahydro‐1‐benzopyrano [4,3‐b]‐1,5‐benzodiazepine derivatives 1–4 have been obtained by resolution of their respective salts with (+)‐ or (−)1,1′‐bi‐2,2′‐naphthyl hydrogen phosphate. Their absolute configurations were assigned by X‐ray analysis of the hydrobromide of the (+)enantiomer 3a and by subsequent comparison of its circular dichroism with those of the other enantiomers. Contrary to the high biological activity of the enantiomer 3a, its antipode 3b was shown to be biologically completely inactive.
The “Normalizing Factor” for the Tomato Mutant chloronerva. XXIII. Deaminonicotianamine and 2‐Decarboxynicotianamine
Authors: Ripperger H. 
Published: December 2004

AbstractDeaminonicotianamine (8) and 2‐decarboxynicotianamine (11) were synthesized by stepwise reductive alkylation of (S)‐2‐ethoxycarbonylazetidine (3) or azetidine (9) with ethyl (S)‐4‐oxo‐2‐(trifluoroacetylamino)butanoate (4) and ethyl 4‐ oxobutanoate (7), respectively. The amino acids 8 or 11 as well as the intermediates, (2S,αS)‐α‐amino‐2‐carboxy‐1‐azetidinebutanoic acid (6) and (S)‐α‐amino‐1‐azetidinebutanoic acid (10) did not show biological activity with regard to chlorophyll synthesis in chlorotic leaflets of the tomato mutant chloronerva. The compound 11 promoted the normally inhibited root growth of the mutant.Nicotianamine (1) has been identified as the “normalizing factor” which restores chlorophyll synthesis, growth and development of the auxotroph mutant chloronerva of Lycopersicon esculentum Mill. [2]. Nicotianamine proved to be widespread in the plant kingdom ([1], cf. [3]). Biochemical experiments revealed a disturbed iron metabolism of the mutant, leading to an excessive iron absorption by the roots on the one hand and an irregular iron distribution within young leaves on the other [4, 5]. Nicotianamine (1) forms stable 1:1 complexes with iron (II) and other bivalent metal ions [6] with high stability constants in comparison with those of bidentate amino acids; e.g. the stability constants for the 1:1 copper complexes of nicotianamine and α‐alanine are 1018.6 [6] and 108.5 [7], respectively. As is evident from a Dreiding model, nicotianamine has an optimal molecular structure for complex formation with metal ions. Not only are six functional groups present, necessary for octahedral coordination, but the distances between the groups are also optimal for the formation of chelate rings: three 5‐membered rings formed by the α‐amino acid residues and two 6‐membered rings formed by the 1,3‐diaminopropane moieties [2, 3]. In order to study whether strong complex formation is important for the biological activity of nicotianamine, a series of synthetic analogues were prepared. The antipode of nicotianamine [8] and the proline analogue [9] were biologically active, further analogues, e.g. homologues with 1,4‐diaminobutane moieties [10], peptides [11] or quadridentate ligands [2, 8, 10] proved to be inactive. The hitherto existing results indicate that a partial structure 2 (or enantiomeric) is essential for the biological activity and that nicotianamine plays an important role in the cellular iron transport and/or metabolism in plants.
Photochemical Dediazoniation of Arene Diazonium Salts sensitized by zinc phthalocyanine tetra(sulfomorpholide)
Authors: Becker H. G. O. , Krüger R. , Schütz R. 
Published: December 2004

AbstractPhoto‐excited zinc phthalocyanine tetra(sulfomorpholide) (ZnPcTSM) sensitizes the dediazoniation of arene diazonium salts via electron transfer. 1ZnPcTSM* reacts with p‐methyl‐, p‐methoxy‐, and p‐diethylamino benzenediazonium tetrafluoroborate, respectively, diffusion‐controlled, 3ZnPcTSM* with rate constants 3.3 × 107, 8.5 × 107, and 1.1 × 108 M−1 s−1.Quantum yields of the dye bleaching by p‐methoxy benzenediazonium tetrafluoroborate show that the singlet reaction proceeds due to symmetry‐allowed back electron transfer with very low efficiency, whereas the triplet reaction reaches the ISC quantum yield at [ArN2⊕] ≈︁ 10−3 M.In the triplet reaction an exciplex is formed as proved by the temperature dependence of the quenching rate constants and direct spectroscopic determination (τexciplex = 157 μs). From ΔG≠ of the quenching reaction the solvation reorganization parameter λ0 and the reaction distance (r = 0.37 nm) are calculated.
On the Mechanism of Hydroperoxide Decomposition by Boric Acid Derivatives
Authors: Kunzelmann Astrid , Lauterbach Gerlinde , Potekhin Vyacheslav Matveevich , Pritzkow Wilhelm , Schmidt‐Renner Wolfgang , Vasina Larisa Fedorovna 
Published: December 2004

AbstractDecomposition of cyclohexane and 1‐methylcyclohexane hydroperoxides in cis‐and trans‐1,4‐dimethylcyclohexane in the presence of boric acid esters results in a non‐stereospecific attack at the tertiary CH bonds of the 1,4‐dimethylcyclohexanes. Mixtures of cis‐ and trans‐1,4‐dimethylcyclohexanols are formed in every case. This proves that the attack of the hydroperoxides at the tertiary CH bonds does not proceed by an aliphatic SE2 mechanism.
Quantenchemische Berechnungen an Radikalen vom Allyltyp: Methylsubstituierte Allylradikale
Authors: Ziegler U. , Ondruschka B. , Köhler H.‐J. 
Published: December 2004

Quantum‐Chemical Calculations on Allyl‐Type Radicals: Methyl‐Substituted Allyl RadicalsMethyl‐substituted allyl radicals were calculated by MINDO/3. Based on heats of formation of planar and perpendicular radicals phenomena like thermodynamic stability and regio as well as stereoselectivity are discussed. It is shown that the semiempirical method has artefacts. But in most of the cases MINDO/3 gives a qualitatively correct description of the chemical behaviour of allyl radicals with respect to experimental details.
Über die bevorzugte Bildung von trans‐Epoxiden bei der Technetiumkatalysierten Flüssigphasenoxidation von cis/trans‐n‐Alkenen
Authors: Rummel Siegbert , Schnurpfeil Dieter 
Published: December 2004

About the Formation of trans‐Epoxides in the Liquid Phase Oxidation of cis/trans‐n‐Alkenes Catalyzed by TechnetiumThe liquid‐phase oxidation of n‐oct‐1‐ene, cis‐oct‐4‐ene and cis/trans mixtures of oct‐4‐ene with molecular oxygen in the presence of the technetium complexes 1 to 10 was studied. Low epoxide yields (≦10%) are characteristic features of the reactions. Pure cis‐oct‐4‐ene and mixtures of cis/trans‐oct‐4‐ene yields in cis/trans‐epoxide ratios lower than 0.05. Isomerization reactions and nucleophilic epoxide ring opening reactions are not responsible for the low epoxide yield and the favoured formation of trans‐epoxide. Epoxide decomposition by a Tc‐catalyzed radical reaction which prefers the cis‐epoxide is discussed.
An Amidoalkylation of Trivalent Phosphorus Compounds with P(O)H Functions Including Acetic Acid Solutions of PCl3, RPCl2 or R2PCl, Diesters of Phosphorus Acid and Phosphorus‐III‐Acids
Authors: Oleksyszyn Jozef 
Published: December 2004

AbstractAn amidoalkylation of PCl3 or its organic derivatives in acetic acid solution takes place because equilibrium between AcOH and exist, leading to hydroxychlorophosphines. Those last compounds undergo an amidoalkylation like other nucleophiles. Based on these data, it was shown that an amidoalkylation reaction is usual for all phosphorus compounds with the R2P(O)H system and provides derivatives with the functions. The scope and limitation of these reactions are discussed.
Strukturabhängige Eigenschaften von Tensiden, untersucht an Reihen von 2‐Alkylsulfaten, Phosphinoxiden und ω‐H‐Perfluorverbindungen
Authors: Greiner Anneliese , Herbst Marrit 
Published: December 2004

Structure‐Dependent Properties of Detergents as Studied at 2‐Alkylsulphates, Phosphine‐oxides, and ω‐H‐Perfluoroalkyl CompoundsCMC values from δ/lg c‐curves were determined for the homologous series of 2‐alkyl‐branched alkylsulphates, dimethyl‐ an diethyl‐phosphine‐oxides and ω‐H‐perfluoroalkyl‐sulfosuccinates. On this basis effective chainlengths were calculated and correlated with other properties as maximum of surface tension depression, wettability and foaming.
Über 1,2‐Umlagerungen und CH‐Einschubreaktionen Acyclischer Alkylidencarbene
Authors: Ondruschka Bernd , Remmler Matthias , Zimmermann Gerhard , Krüger Christian 
Published: December 2004

On 1.2‐Shift Reactions and CH‐Insertions of Acyclic Alkylidene CarbenesTwo series of acyclic terminal vinyl bromides (1…4 and 5…7) were tested in the reaction with potassium tert‐butoxide as precursors of alkylidene carbenes. As expected 1 up to 4 only give 1‐alkynes whereas the 2‐methylated vinyl bromides 5, 6 and 7 yield 1‐methylated cyclopentenes predominantly besides 2‐alkynes. The formation of cyclopentenes indicates a reaction route via alkylidene carbenes and 1,5‐CH‐insertion reactions, that of 2‐alkynes is convincing evidence for 1,2‐alkyl shift reactions in 2‐methyl substituted alkylidene carbenes. The selectivity of 1,5‐CH‐insertion depends on the degree of alkyl substitution of the C‐5‐atom. At 240°C the selectivity is 1°:2°:3° ≈ 1:54:240.
α,β‐Unsaturated nitriles in heterocyclic synthesis. II. Synthesis of Pyrazolo[3,4‐b]pyridine and Pyrazolo[1,5‐a]pyrimidine derivatives of antipyrine
Authors: Elagamey Abdel Ghani Ali , El‐Taweal Fathy Mohamed Abdel‐Aziz , Amer Fathy Abdel Kader 
Published: December 2004

Abstract5‐Amino‐3‐antipyrinyl‐pyrazole (1) reacted with cinnamonitriles 2a and 2c, d to afford 5‐amino‐4‐benzylidene‐pyrazole derivatives 3a, b. Compound 1 reacted with two moles of 2a to yield pyrazolo[3,4‐b]pyridine derivative 7a which could be also obtained from the reaction of 3a with 2a. The reaction of 1 with α‐cyanochalcone 2e resulted in the formation of pyrazolo‐[1,5‐a]pyrimidine derivative 8.