bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and reactions of 3‐OXO‐2H‐furan derivatives
Authors: de Rijke D. , Boelens H. 
Published: September 2010

Abstract2‐Alkyl‐4‐ethoxycarbonyl‐5‐methyl‐3‐oxo‐2H‐furans (I, R′ = Et) can be prepared at − 20° from ethyl acetoacetate and α‐bromo carboxylic acid chlorides. The furans do not enolize to hydroxyfurans, but behave essentially as unsaturated ketones towards various nucleophiles. With potassium hydroxide, ring opening and closure leads ultimately to 3‐acetyl‐5‐alkyl‐4‐hydroxy‐2‐oxo‐5H‐furans (II); with sodium methoxide the overall process is one of decarboxylation while oxidative decarboxylation with hydrogen peroxide in an alkaline medium yields 2‐alkyl‐4‐hydroxy‐5‐methyl‐3‐oxo‐2H‐furans (IV). As illustrated in Scheme 1 all three processes are thought to be initiated by the addition of a nucleophile (HO−, CH3O−, HOO−) on the activated double bond in the furans.
Chemistry of acetylenic ethers 100: Dialkyl(methylthioethynyl)phosphine oxides; synthesis and reactions
Authors: Hagens W. , Bos H. J. T. , Arens J. F. 
Published: September 2010

AbstractThe directiospecificity and stereochemistry of the addition of nucleophiles (Me2NH, MeS⊖ and MeO⊖), of electrophiles (HCl and H3O⊕) and of the free radical C2H5S to Me2P(O)CCSMe and Et2P(O)CCSMe have been studied. The structural assignment of the adducts was based on PMR (Table II); coupling constants 2JPH in R2P(O)CHCYZ decrease with increasing electronegativity of Y and Z.
Bicyclic γ‐lactone formation in the Reformatsky reaction with 2‐substituted cyclopentanones
Authors: Ward J.P. 
Published: September 2010

AbstractBicyclic γ‐lactones were found among the products of reaction of two 2‐substituted cyclopentanones with bromoacetic esters and zinc (Reformatsky). The intermediate β‐hydroxy‐acid obtained from 2‐pentylcyclopentanone with zinc and tert‐butyl bromoacetate in benzene was converted to 4‐pentyl‐3,4‐trimethylene‐4‐butanolide in 67% yield. The preparation of 1‐(2‐carboxyethyl)‐2‐(7‐carboxyheptyl)cyclopentene is described.
Kinetics of water‐ammonia exchange in the series of aquaamminecobalt(III) complexes: II. Reactivity difference between cis‐ and trans‐aquahydroxotetraamminecobalt(III) ions in the reaction with ammonia
Authors: Bohte E.G.A.M. , Balt S. 
Published: September 2010

AbstractThe reactions of dihydroxotetraamminecobalt(III) perchlorate have been studied in an aqueous solution of 8M‐ammonia containing 1.80M‐ammonium perchlorate, at 25°. Under these conditions the isomerization and the uptake of ammonia occur at comparable rates. From the analysis of the absorbance as a function of time it followed that cis and trans ions react with ammonia at nearly equal rates. On the basis of this information the steric factor in the labilization of Co(III) ligand bonds by a coordinated hydroxo group is discussed.
New macrocyclic compounds from the secretions of the civet cat and the musk rat
Authors: van Dorp D.A. , Klok R. , Nugteren D.H. 
Published: September 2010

AbstractThe odoriferous glands of the civet cat and the musk rat contain not only the limited number of macrocyclic components described in the classical literature, such as civetone (9cis‐cycloheptadecenone), but a whole spectrum of saturated and unsaturated cyclic ketones and alcohols. In the musk rat, peculiar compounds containing conjugated and/or triple bonds were found; the unsaturation was located here exclusively at the 5 and/or 7 position. The macrocyclic alcohols were always esterified with long chain fatty acids. The absolute configuration of the dextrorotatory unsaturated alcohols was established as S. Some of the new compounds have been made in quantity by total organic synthesis, viz. 5‐cyclopentadecynone, 5cis‐cyclopentadecenone, 5‐cycloheptadecynone, 5cis‐cycloheptadecenone and 9cis‐cyclononadecenone.
A study of π‐conjugation in Chichibabin's ‐ and Schlenk's ‐ like hydrocarbons with ESR: Part i
Authors: Kooistra By C. , van Dijk J. M. F. , van Lier P. M. , Buck H. M. 
Published: September 2010

AbstractAnalysis of the ESR spectrum of the radical cation, derived from p, p′‐bis‐{phenyl(triphenylphosphorylidene)methyl}biphenyl reveals that spin density is found at both 31P nuclei. Zero spin density is indicated for the outer phenyl rings. In the radical cation, derived from the corresponding m,m′‐isomer the spin density is delocalized over one half of the molecule and interaction is found with only one phosphorus atom. In this system the spin density in the outside ring exceeds that in the biphenyl ring. The localization of the odd electron on one half of the molecule must be caused by a strong Jahn‐Teller effect.The assignment of the hyperfine coupling constants was based on spin density calculations according to the Unrestricted Hartree‐Fock (UHF) method. From these calculations we also obtained an indication of the geometry of the radicals.The synthesis of these compounds is reported.
PMR‐spectra of some diastereoisomeric ionol isomers in the presence of EUIII‐2,2,6,6‐tetramethylheptadionate
Authors: Kruk C. , Roof A. A. M. , van Wageningen A. , Cerfontain H. 
Published: September 2010

AbstractPMR‐spectra of diastereoisomers containing two chiral centres can be elucidated by complexation with the EuIII‐heptadionate shift reagent, as is illustrated for the two pairs of diastereoisomers of both (E)‐α‐ionol (I) and the bicyclic ionol II.
Vinyl orthoformates and vinyl acetals. Part iii: The reactions of alkenyl acetals and l‐alkenyloxyalkyl carboxylates with carboxylic acids
Authors: van Melick J. E. W. , Posno T. , Scheeren J. W. , Nivard R. J. F. 
Published: September 2010

AbstractTreatment of alkenyl acetals IV with one equivalent of a carboxylic acid leads to the formation of either addition products, l‐acyloxyalkyl alkenyl acetals VI, or substitution products, l‐alkenyloxyalkyl carboxylates V, dependent upon the structure of the starting compounds. In a similar way the l‐alkenyloxyalkyl carboxylates V give 1,1′‐diacyloxy ethers X, or acylals XI, with a second equivalent of a carboxylic acid. Synthetic applications and tentative reaction schemes of these conversions are given.
Some aspects of the electronic spectra of 1,3‐cyclohexadiene, (E)‐ and (Z)‐1,3,5‐hexatriene
Authors: Minnaard N. G. , Havinga E. 
Published: September 2010

AbstractThe electronic spectra of 1,3‐cyclohexadiene, (Z)‐ and (E)‐1,3,5‐hexatriene were measured and interpreted.The absorptions between 220 and 280 nm in the gas phase are π → πx‐transitions whereas the second absorption (180‐210 nm) in these compounds is considered to be a Rydberg transition. A weak π → πx‐transition is hidden by the latter absorption in (Z)‐hexatriene. The band in the solution spectrum of cyclohexadiene at 190 nm is thought to correspond to the band at 175 nm in gaseous cyclohexadiene.Triplet absorption spectra were measured in heavy atom solvents (CH2I2, CHBr3).A scheme of energy levels is given.
Preparation and ESR of phosphorus spiro compounds. Part II: Stereo‐isomerization of organo‐phosphorus radicals
Authors: Rothuis R. , Freide J. J. H. M. Font , Buck H. M. 
Published: September 2010

AbstractThe synthesis of bis{2,2î‐(5,5î‐dimethoxy)biphenylenephosphonium and bis {2,2′‐(5,5′‐dimethylamino)biphenylene}phosphonium salts is described. The related spiro phosphoranyl radicals II and III, generated by electrochemical reduction, are measured by means of ESR spectroscopy. We observed the same small values of the phosphorus doublet splitting constants as for the bis(2,2′‐biphenylene)phosphoranyl radical I.In this investigation we found also that the radical obtained by photolysis of bis(2,2′‐biphenylene)phosphorane at −120° appeared to be identical with the radical obtained by electrochemical reduction of the bis(2,2′‐biphenylene)phosphonium ion. Irradiation of the phosphorane which has a trigonal bipyramidal (TBP) configuration results in a cleavage of the equatorial hydrogen atom. The small values of the phosphorus doublet splitting constants give rise to a tetrahedron like (T) configuration in which the unpaired electron is delocalized in the aryl ligands.We also discuss the associative character of these radicals in dependence on the temperature.
New aspects of the oxygen uptake by Rh(PPh3)3Cl ESR and kinetic results
Authors: van Vugt Barry H. , Koole N. J. , Drenth W. , Kuijpers F. P. J. 
Published: September 2010

AbstractThe rate of oxygenation of Rh(PPh3)3Cl in benzene was measured at 50°C. ESR measurements suggest the presence of a Rh(II)·· O2 species. A mechanism is proposed for this oxygenation and for the subsequent oxidation of one phosphine ligand.
Deazapurine derivatives XII. Investigations on the synthesis of 3‐deazaguanine
Authors: de Bode R. , Salemink C.A. 
Published: September 2010

AbstractThe attempted synthesis of 3‐deazaguanine along two pathways has lead to several new imidazo[4,5‐c]pyridines. 3‐Deazaguanine itself could not be isolated from the preceding 2‐(carbamate acetyl‐)amino‐derivative.
Electrochemical reduction of arenesulfonyl cyanides
Authors: van der Meer D. , Spaans A. , Thijsse H. 
Published: September 2010

AbstractBenzenesulfonyl cyanide and six para‐substitution products were reduced electrochemically at a dropping mercury cathode, in DMF as solvent. A linear Hammett relation between the half‐wave potentials of the first reduction wave and the σx‐values was observed. This suggests the reduction mechanism being analogous for all molecules studied. The half‐wave potentials could not be correlated with the electron affinities of these molecules, since for all compounds the first reduction wave is irreversible, due to the formation of mercurous intermediates. Performing electrochemical reduction within the ESR cavity spectra were obtained in some cases. For p‐cyanobenzenesulfonyl and p‐nitrobenzenesulfonyl cyanides these ESR spectra could be analysed and were assigned to the p‐cyanobenzenesulfonyl and p‐nitrobenzenesulfonyl dianion radicals, respectively. Prolonged reduction of p‐nitrobenzenesulfonyl cyanide in DMF yields two additional ESR spectra, which could be assigned to the p‐nitrobenzenesulfinyl and p‐nitrobenzenesulfenyl dianions. So the SO2 group is reduced selectively in presence of the NO2 group.
Reductive ring opening of thiazoles
Authors: Hoff S. , Blok A.P. 
Published: September 2010

AbstractThe course of the reductive ring‐opening reactions of 2‐mercapto‐, 2‐hydroxy, 2‐amino‐, 2‐methylamino‐ and 2‐dimethylamino‐4‐methylthiazoles with sodium in liquid ammonia, yielding substituted propenethiolates, has been found to depend on the nature of the hetero substituent. The mechanism of the ring opening is discussed.
Base‐catalysed cyclisation of 2‐alkynyl alkanedithioates (with a note on the preparation of O‐alkyl thioates)
Authors: Vermeer P. , Meijer J. , Bos H. J. T. , Brandsma L. 
Published: September 2010

Abstract2‐Alkynyl alkanedithioates R1R2CHC(S)‐S‐CH(R3)CCR4 (1, R1 = CH3; R2‐R4 = H or CH3) cyclise on treatment with NaOC2H5 in ethanol to 2,4‐dialkylidene‐1,3‐dithiolanes, 7; if ButOK in 1,2‐dimethoxyethane (DME) is used as a base, the end products are 1,3‐dithiole derivatives 8.
Ring transformations in reactions of heterocyclic halogeno compounds with nucleophiles (XXXIV): Ring contraction of 4‐chloropyrimidine‐1‐oxides into isoxazoles in liquid ammonia
Authors: Peereboom R. , van der Plas H. C. , Koudijs A. 
Published: September 2010

AbstractIn the reaction of 4‐chloro‐6‐R‐pyrimidine‐1‐oxides (R=CH3 or C6H5) with potassium amide in liquid ammonia at −75°C or with liquid ammonia at −33°C besides the formation of the corresponding 4‐aminopyrimidine‐N‐oxides, a ring contraction into 5‐amino‐3‐R‐isoxazoles (R=CH3 or C6H5) has been observed.A mechanism for the ring contraction reaction is postulated.
Chemistry of alkenethiolates IV: Synthesis and reactions of 1,3‐dithiolane‐2‐thiones and thiazolidine‐2‐thiones
Authors: Hoff S. , Blok A. P. 
Published: September 2010

Abstract2‐Acetamidoalkenethiolates (1) have been caused to react with several heterocumulenes. Carbon disulfide gave good yields of substituted 4‐acetamido‐1,3‐dithiolane‐2‐thiones (3), which rearranged thermally to thiazoles. Isothiocyanates afforded 4‐acetamidothiazolidine‐2‐thiones (8).
Ring transformations in reactions of heterocyclic compounds with nucleophiles [VII]N‐demethylation during the reaction of N‐methylpyrimidinium salts with liquid ammonia
Authors: Oostveen E. A. , van der Plas H. C. , Jongejan H. 
Published: September 2010

AbstractOn treatment with liquid ammonia at −33°C, the quaternary pyrimidinium salts, i.e. 1‐methylpyrimidinium methyl sulfate (4a), 1,2‐dimethylpyrimidinium iodide (4b), 1,4,6‐trimethyl‐pyrimidinium iodide (4c) and 1,2,4,6‐tetramethylpyrimidinium iodide (4d) demethylate yielding pyrimidine, 2‐methyl‐, 4,6‐dimethyl‐ and 2,4,6‐trimethylpyrimidine, respectively. It was observed that under these conditions 1‐methyl‐[1.3‐15N]‐pyrimidinium methyl sulfate yields [1‐15N]‐pyrimidine. By measuring the PMR spectra of above‐mentioned pyrimidinium salts in liquid ammonia it is shown that these salts undergo covalent amination on the 1,6‐azomethine bond. These results indicate that the demethylation reaction occurs via an Addition‐Nucleophile‐Ring‐Opening‐Ring Closure mechanism.
On the optical purity of synthetic thyrotropin‐releasing hormone
Authors: Syrier J. L. M. , Beyerman H. C. 
Published: September 2010

AbstractIt was demonstrated that considerable racemization of histidine took place in our preceding synthesis of thyrotropin‐releasing hormone (TRH), pyroglutamyl‐histidyl‐proline amide, <Glu‐His‐Pro‐NH2. This racemization was caused by application of Nim‐benzyl protection of histidine and could now be suppressed by addition of 1‐hydroxy‐1H‐benzotriazole in the dicyclohexyl‐carbodiimide‐mediated couplings.The efficiency of our TRH synthesis was compared with some other syntheses on a solid support and in solution.
ESCA‐investigations of copper(II) salts of β‐dicarbonyl compounds
Authors: Kolind‐Andersen H. , Lawesson S.‐O. , Folkesson B. 
Published: September 2010

AbstractThe binding energies of the Cu(2p3/2) electrons in various copper(II) salts of β‐dicarbonyl compounds have been measured. The binding energies are correlated with the σ‐constatnts of the substituents on the heterocyclic six‐membered ring formed by the ligand and the metal atom. It is observed that electron‐donating substituents diminish the binding energy of the core electrons on the copper atom. The binding energies are also correlated with the most highly energetic of the IR frequencies in the carbonyl and carbon double bond region originating from the six‐membered ring.
Conformation of non‐aromatic ring compounds ‐ 84 Dipole moments and 100 MHz Fourier‐transform Proton Magnetic Resonance spectra of some substituted 3‐phenylglutaric anhydrides; a conformational analysis
Authors: Koer F. J. , Altona C. 
Published: September 2010

AbstractThe dipole moments and PMR spectra of a series of 3‐(p‐X‐phenyl)glutaric anhydrides [X: H (2), F (3), Cl (4), Br (5), NO2 (6)] and of 3‐(p‐chlorophenyl)‐3‐methylglutaric anhydride (7) were measured and interpreted in terms of conformational properties of the anhydride ring and its side‐chain. The dipole moments of 2‐7 (measured in benzene) were 4.73, 3.82, 3.66, 3.70, 2.53 and 4.59 Debyes, respectively. Theoretical dipole moments for the individual conformers were calculated from atomic coordinates of model structures and standard point charges. The equilibrium compositions derived from vicinal proton coupling constants are compared with those obtained from the dipole moments. A satisfactory agreement is noted. The p‐X‐C6H4 group in 2‐6 is shown to prefer the equatorial Epl conformation (Ph//βH) over the axial Apr conformation (Ph // βH) to the extent of 0.6‐1.2 kcal/mol. In compound 7 the equatorial Ph group probably takes up the Epr conformation.
Deazapurine derivatives XIII 5,7‐Disubstituted imidazo[4,5‐b]pyridines. A new synthesis of 1‐deazaguanine
Authors: Schelling J. E. , Salemink C. A. 
Published: September 2010

AbstractA number of 7‐substituted‐5‐acetamido imidazo[4,5‐b]pyridines, useful in ribose coupling reactions, were synthesized by application of the ring‐closure reaction with ethyl orthoformate and acetic anhydride. A new synthesis of 1‐deazaguanine, using mild reaction conditions and a possible preparation of 1‐deazaxanthine is described.
Analgetics: Part I. The crystal structure of pethidine hydrochloride, 4‐carbethoxy‐1‐methyl‐4‐phenylpiperdine hydrochloride, C15H21NO2.HCl
Authors: Tillack J. V. , Seccombe R. C. , Kennard C. H. L. , Oh P. W. T. 
Published: September 2010

AbstractThe crystal structure of pethidine hydrochloride, 4‐carbethoxy‐1‐methyl‐4‐phenylpiperidine hydrochloride, C15H21NO2.HCl, was determined from three dimensional diffractometer data with 2886 reflections. There are eight molecules in the monoclinic unit cell, space group, P21/c, a = 2262 (2), b = 1153 (4), c = 1183 (1) pm, β = 90.00(5)°. Refinement was halted when R = 0.12. In the two independent molecules in the asymmetric unit, the phenylring is equatorial to the piperidine ring. However, the molecules differ in the orientation of carbethoxy‐group.
Reactivities of 3‐ and 4‐halogenopyridines towards potassium tert‐butoxide and potassium benzenethiolate (thiophenoxide) in dimethyl sulfoxide
Authors: van Zoest W. J. , den Hertog H. J. 
Published: September 2010

AbstractWhen 3‐ and 4‐fluoropyridine are treated with a mixture of potassium tert‐butoxide and potassium benzenethiolate (thiophenoxide) in dimethyl sulfoxide (DMSO), they are converted into the corresponding tert‐butoxypyridines by an addition‐elimination mechanism. The 3‐ and 4‐bromo‐and‐iodo‐pyridines react mainly by the EA‐mechanism via 3,4‐didehydropyridine producing mixtures of principally 3‐ and 4‐(phenylthio)pyridine and partly according to the AE‐mechanism with potassium benzenethiolate.Reactivities of the halogenopyridines towards potassium tert‐butoxide and potassium benzenethiolate are compared with those towards other bases. The formation of 3,4‐didehydropyridine as an intermediate in the reactions of 3‐bromopyridine with both potassium tert‐butoxide and potassium amide was confirmed by trapping it with furan.
Adenylyl‐uridine. Assignment and analysis of the 270 Mhz fast Fourier transform proton magnetic resonance spectrum
Authors: Altona Cornelis , Koeners Herman J. , de Jager Jenny R. , van Boom Jacques H. , van Binst G. 
Published: September 2010

AbstractThe fast Fourier‐transform proton magnetic spectrum of Adenylyl‐uridine (ApU) was taken at 270 MHz. The complex group of signals due to the ribose protons could be analyzed to yield chemical shifts. 1H1H and 1H31P coupling constants. The assignment of the various peaks was based mainly on the known assignment of the N6‐monomethylated analogue m6ApU, see C. Altona et al., Nature 247, 558 (1974). Best values of the chemical shifts and coupling constants of ApU were obtained by carrying out a series of computer simulations of line shapes and intensities.
Stereochemistry of cyclopropane ring hydrogenolysis
Authors: Kieboom A. P. G. , Breijer A. J. , van Bekkum H. 
Published: September 2010

AbstractThe hydrogenolysis of trans‐1,2‐dimethyl‐1,2‐diphenylcyclopropane has been studied using palladium, platinum, rhodium and Raney‐nickel as the catalysts. The latter three metals show a rather low stereospecificity, i.e. 40% suprafacial versus 60% antarafacial hydrogen addition to the C‐1 and C‐2 atoms, whereas on palladium this ratio is 80:20. However, when a strong acid is present, antarafacial hydrogen addition predominates on palladium due to protonation of the cyclopropane ring during the hydrogenolytic cleavage process.
Proton‐catalysed hydride‐transfer from alkanes to methylated benzyl cations. Part II: Spectroscopy and kinetics; isotope‐effects for proton‐exchange and hydridetransfer
Authors: van Pelt P. , Buck H. M. 
Published: September 2010

AbstractThe PMR and UV spectra of para‐X substituted 2,3,5,6‐tetramethylbenzyl cations II (a‐f) (X = OCH3, CH3, F, Br, H, NO2) are discussed and from the solvolytic behaviour of the parent benzyl chlorides the stability of these ions is found to be IIa > IIb > IIc > IId ∼ IIe > IIf. Proton exchange between [2‐3H]isobutane and HSO3F is found to have a small isotope effect of 6.5 at − 74°. The hydride‐transfer reaction between labelled isobutane and ions IIb has a larger isotope‐effect, estimated to be about 20. A termolecular transition state where transferred hydrogen is symmetrically bonded is proposed for the hydride‐transfer reaction.
Synthesis of 19‐cis‐docosenoic, 17‐cis‐eicosenoic and 15‐cis‐octadecenoic acid
Authors: Klok R. , Egmond G. J. N. , Pabon H. J. J. 
Published: September 2010

AbstractLarge‐scale syntheses of 19‐cis‐docosenoic, 17‐cis‐eicosenoic and 15‐cis‐octadecenoic acid by chain extension of 8‐undecynoic acid via Kolbe's anodic synthesis, as well as by coupling of 1‐butyne with n‐bromoalkanoic acids were found unsuitable. Therefore, 15‐octadecynoic acid was prepared on a large scale from 13‐hexadecyn‐1‐ol by malonic ester coupling. Esterification and reduction with lithium aluminium hydride yielded 15‐octadecyn‐1‐ol. Converting the latter into a methanesulfonate followed by malonic ester synthesis yielded 17‐eicosynoic acid, which, in turn, was converted by the same sequence of reaction steps into 19‐docosynoic acid. Hydrogenation of the acetylenic acids in the presence of Lindlar's catalyst yielded the title compounds.
On the occurrence of the SN(ANRORC) mechanism in the amination of 2‐halogeno‐4,6‐diphenylpyrimidines and 2‐chloro‐ and 4‐chloro‐quinazolines
Authors: Kroon A. P. , van der Plas H. C. 
Published: September 2010

AbstractAmination of the 2‐X‐4,6‐diphenylpyrimidines (X=F, Cl, Br) with potassium amide in liquid ammonia yields the corresponding 2‐amino compounds, and in addition some dehalogenated product in the case of X = Br. It is proved, using the corresponding [1,3‐15N]‐labelled pyrimidines, that for the 2‐chloro and 2‐bromo compounds the amination goes to the extent of about 70% via a ring‐opening [SN(ANRORC) mechanism] but that in the amination of the 2‐fluoro compound no ring‐opening takes place [SN(AE) process]. One of the supposed intermediates during the ring‐opening i.e. 3‐(cyanoimino)‐1,3‐diphenyl‐1‐propenamine could be isolated.Also the amination of 2‐chloro‐4‐phenylquinazoline with potassium amide occurs to the extent of about 70% via the SN(ANRORC) mechanism. If instead of potassium amide in liquid ammonia an ethanolic ammonia solution is used at elevated temperatures, a considerable amount of the corresponding 2‐amino compound is also formed via the ring‐opening process, i.e. 34‐67% (depending on the ammonia concentration). 2‐Chloro‐ and 4‐chloro‐quinazoline behave similarly on reaction with ethanolic ammonia.
Ring transformations in reactions of heterocyclic halogeno compounds with nucleophiles (XXXVI). Conversion of 4‐amino‐3‐halogenopyridazines into pyrazoles and of 4‐amino‐3,6‐dihalogenopyridazines into 1,2,4‐triazoles
Authors: Klinge D. E. , van der Plas H. C. , Geurtsen G. , Koudijs A. 
Published: September 2010

AbstractOn treatment of 4‐amino‐3‐X‐pyridazine (X=Cl, Br) with potassium amide in liquid ammonia 4‐cyanopyrazole is formed. Under the same reaction conditions 4‐amino‐3,6‐di‐X‐pyridazine (X=Cl, Br) undergoes a ring contraction into 3‐(cyanomethyl)‐1,2,4‐triazole.The mechanism of both ring contractions is discussed.
Koch‐Haaf carboxylations. Part III. Exchange phenomena during Koch‐Haaf carboxylations in sulfuric acid‐d2
Authors: Peters J. A. , Rog J. , van Bekkum H. 
Published: September 2010

AbstractIt is shown that during the Koch‐Haaf carboxylation of 3‐ and 4‐methylcyclohexanols the isomerisation of the intermediate secondary carbenium ion to the tertiary 1‐methylcyclohexyl cation proceeds via a succession of 1,2‐hydride shifts. By using D2SO4 as the reaction medium the latter cation is shown to be in rapid interconversion with 1‐methylcyclohexene and methylenecyclohexane. The intermediacy of alkenes in some other Koch‐Haaf carboxylations is demonstrated. On the basis of H/D exchange of some carboxylic acids in D2SO4HCOOH, the reversibility of the Koch reaction under different reaction conditions is discussed.