bluuebunny/crossref_metadata_2025 huggingface dataset:
Proton magnetic resonance studies of specifically deuterated cyclohexane compounds. Part IV. 1,1‐Dimethylcyclohexane, 1,3‐ and 1,4‐di‐t‐butylcyclohexane (cis and trans), and cis,cis‐1,3,5‐tri‐t‐butylcyclohexane
Authors: Remijnse J. D. , van Bekkum H. , Wepster B. M.
Published: September 2010

This paper describes the preparation and a PMR investigation of a series of deuterium derivatives of 1,1‐dimethylcyclohexane, cis‐ and trans‐1,3‐ and 1,4‐di‐t‐butylcyclohexane, and cis,cis‐1,3,5‐tri‐t‐butylcyclohexane. Accurate PMR parameters are obtained by the application of deuterium decoupling and computer simulation and iteration of the spectra. The coupling constants in trans‐1,4‐di‐t‐butylcyclohexane show that the t‐butyl sides of the ring are puckered to the same extent as in t‐butylcyclohexane. In cis‐1,3‐di‐t‐butylcyclohexane and cis,cis‐1,3,5‐tri‐t‐butylcyclohexané the axial protons at the carbon atoms between the t‐butyl groups are also bent towards the centre of the ring. The axial methyl group in 1,1‐dimethylcyclohexane is shown to cause a flattening of the ring. The chemical shifts of the ring protons provide further insight into the “anomalous” shift of 2‐axial protons in methylcyclohexane(s).

The vicinal coupling constants of trans‐1,3‐di‐t‐butylcyclohexane confirm that this compound exists for the greater part in a twist conformation.
The preparation of the eight‐membered ring system (NPCl2)3NSOCl
Authors: Voswijk C. , van de Grampel J. C.
Published: September 2010

From the reaction mixture of [Cl3P=N‐PCl2=N‐PCl3] + [PCl6]− and SO2(NH2)2 (molar ratio 1:1) a solid with formula (NPCl2)3NSOCl could be isolated in small yield. The IR and mass spectrum of this eight‐membered ring system are discussed.
Conformational analysis of some alkylbenzene derivatives Part III: The barriers to rotation and the preferred conformations of some hydroxy‐alkyl groups in 1‐(1‐hydroxyalkyl)‐3,4,5‐trimethoxybenzenes
Authors: Baas J. M. A. , van der Toorn J. M. , Wepster B. M.
Published: September 2010

The barriers to rotation about the Cal‐Car bond of six hydroxyalkyl groups in 1‐C(OH)‐R1R2‐3,4,5‐trimethoxybenzenes have been determined from the coalescence of the PMR signals for the aromatic hydrogen atoms. The coalescence temperatures (°C) and the free energies of activation (kcal/mole) measured for the groups substituted with R1 and R2 are, respectively: But, H, −96, 8.7; But, Et, −38, 11.3; But. Pr, −40, 11.3; But, Bu, −38, 11.4; But, Pri, −8, 13.0; Pri, Pri, −42, 11.2. The heights of the barriers to rotation and the preferred conformations of the hydroxyalkyl groups with respect to the plane of the benzene ring are discussed.
A comparison of properties of 3,4‐dibromo and 3,4‐dichloro derivatives of 1,6‐and 1,7‐naphthyridine
Authors: Czuba W. , Woźniak M.
Published: September 2010

Differences have been found in the reactivity of halogens in positions 3 and 4 of 1,6‐naphthyridine. The differences were observed in the reaction of 3,4‐dihalogenonaphthyridines with p‐toluenesulfonic hydrazide. Convenient methods are described for the synthesis of 3‐bromo‐ and 3‐chloro‐1,6‐naphthyridine.
Photochemical additions of o‐quinones and benzil to conjugated alkenynes
Authors: Koster R. J. C. , Streefkerk D. G. , Oudshoorn‐van Veen J. , Bos H. J. T.
Published: September 2010

Phenanthraquinone (PQ) and tetrachloro‐o‐benzoquinone were added photochemically to the double bond of various substituted alkenynes (1), yielding dihydrodioxin derivatives (2, 5); in some cases oxetane derivatives (4) were isolated too. Generally the photochemical addition occurred non‐stereospecifically. Reversible additions of PQ to the double bond were established. Thermal additions of tetrachloro‐o‐benzoquinone occurred with retention of configuration. The photochemical addition of benzil to conjugated alkenynes and to alkenes, however, led to oxetanes (6) only.
Kinetics of water‐ammonia exchange in the series of aquaamminecobalt(III) complexes. IV. Rates of interconversion reactions between the tetraammine and pentaammine ions
Authors: Bohte E. G. A. M. , Balt S.
Published: September 2010

The kinetics of base hydrolysis of the Co(NH3)5OH2+ ion have been studied as a function of pH, ammonia concentration and temperature. The reaction takes the route via outer sphere complexes of the pentaammine ion or its conjugate base. The actual process can be understood as a dissociative interchange of ammonia from the first coordination sphere and hydroxyl ions (or possibly water) from the second sphere. Also rate constants for the reverse reaction are compared with previously determined values. The conjugate base mechanism, one of the routes for the reaction of the tetraammine ion with NH3, is put on a more quantitative basis.
Cycliacylation of 3‐phenylpropanoic and 4‐phenylbutanoic acids in liquid hydrogen fluoride: Kinetics, mechanism and substituent effects
Authors: Brouwer D. M. , van Doorn J. A. , Kiffen A. A. , Kramer P. A.
Published: September 2010

A kinetic study has been made of the cycliacylation in liquid HF of protonated 3‐phenylpropanoic and 4‐phenylbutanoic acids and a number of their alkyl derivatives to the corresponding 1‐indanones and 1‐tetralones*. The acylating species in these reactions has been shown to be the free acyl cation. Formation of this cation becomes rate‐determining at high rates of the cyclization step proper and then masks any further activation of the benzene ring. The cyclization to 1‐indanones, but not that to 1‐tetralones, exhibits an unusually large ortho partial rate factor (for methyl groups fo is as large as fp). PMR spectroscopic data indicate that replacement of the benzylic hydrogen atoms in 3‐phenylpropanoic acids by methyl groups has a great influence on the conformation around the C(2)‐C(3) bond. This results in a proximity effect that accelerates the cyclization reaction by a factor of about 102.
Didehydrohetarenes (XXXIII). Evidence for a 4,5‐didehydropyridazine in the amination of 4‐halogenopyridazines with potassium amide in liquid ammonia
Authors: Klinge D. E. , van der Plas H. C. , Koudijs A.
Published: September 2010

4‐X‐3‐(methoxymethyl)‐6‐methylpyridazine (X = Cl, Br, I) on treatment with potassium amide in liquid ammonia at − 33°C gives a mixture of 4‐ and 5‐amino‐3‐(methoxymethyl)‐6‐methylpyridazine (ratio 1: 5), which ratio is independent of the nature of the halogen atom. A 4,5‐didehydropyridazine is proposed as intermediate.
Penta co‐ordinated organo‐phosphorus compounds as model substances for simulation of biochemical conversions. Part I. A model description for the specific interaction t‐RNA synthetase‐amino acid; a selection procedure
Authors: Voncken W. G. , Buck H. M.
Published: September 2010

It is demonstrated that the O‐alkylation of acids and phenols with oxaphospholenes can be used as a model system for biochemical conversions. The mechanism of the acylation of Coenzyme A and a selection procedure for amino acids by the t‐RNA synthetases are described with the aid of the model system.
Ring transformations in reactions of heterocyclic compounds with nucleophiles (VIII). Conversion of pyrimidines into isoxazoles
Authors: van der Plas H. C. , Vollering M. C. , Jongejan H. , Zuurdeeg B.
Published: September 2010

When pyrimidine, 1‐methylpyrimidinium methosulfate, 1,3‐diethylpyrimidinium tetrafluoroborate or pyrimidine N‐oxide is reacted with hydroxylamine hydrochloride, isoxazole is formed in a good yield. On reaction of 4,6‐dimethylpyrimidine and its corresponding N‐oxide with the same reagent 3,5‐dimethylisoxazole is obtained. Similarly, from 6‐methyl‐4‐phenylpyrimidine 1‐oxide 3‐methyl‐5‐phenylisoxazole is formed. It has been found by 15N‐labelling experiments that the NO moiety of the isoxazole ring originates from the hydroxylamine and not from the magnified image function of the pyrimidine N‐oxide.
PMR‐studies on the formation of adducts between 4‐substituted‐5‐bromopyrimidines and potassium amide in liquid ammonia
Authors: Geerts J. P. , Rasmussen C. A. H. , van der Plas H. C. , van Veldhuizen A.
Published: September 2010

PMR‐spectra of some 5‐bromo‐4‐R‐pyrimidines (R=Ph, But, OMe, PhMeN, MeNH, Me) in KNH2/liquid NH3 are described. Evidence is presented for the formation of stable σ‐adducts by attack of an amide ion on C6 of the pyrimidine ring in the cases of R=Ph, But, OMe, PhMeN. When the C4‐substituent contains an acidic hydrogen atom α to the aromatic nucleus (R=MeNH, Me), deprotonation occurs and in the case of R=Me also adduct formation has been observed.
Chemistry of acetylenic ethers 105. Addition of organocopper(I) reagents to 1‐alkynyl sulfoxides
Authors: Vermeer P. , Meijer J. , Eylander C.
Published: September 2010

Organocopper(I) reagents R1Cu add readily to l‐alkynyl sulfoxides R2CCS(O)R3 with the formation of vinylic sulfoxides R1R2CCHS(O)R3 in high yields. The addition proceeds in a stereospecific manner.
Synthesis of 1‐(methylthio)propyl propenyl disulfide and sec‐butyl 3‐(methylthio)allyl disulfide, two pesticides from asa foetida
Authors: Meijer J. , Vermeer P.
Published: September 2010

1‐(Methylthio)propyl propenyl disulfide (IV) and sec‐butyl 3‐(methylthio)allyl disulfide (VII), isolated from Asa foetida, have been synthetisized in reasonable yields, starting from methyl dithiopropionate and 1‐(methylthio)‐3‐chloropropene respectively.
Diversity in the course of the reactions of the 4‐halogenoisoquinolines with potassium amide in liquid ammonia and with piperidine
Authors: Sanders Georgine M. , van Dijk M. , den Hertog H. J.
Published: September 2010

The reactions of the 4‐X‐isoquinolines (X=F, Cl, Br, I) with potassium amide in liquid ammonia were investigated. In amounts depending on the halogen present, 1‐amino‐4‐X‐isoquinoline and 1‐aminoisoquinoline are formed by a Chichibabin‐type reaction and an abnormal AE mechanism, respectively. Evidence for the intermediate tetrahedral complex in position 1 was obtained by PMR measurements on 4‐chloroisoquinoline. In the case of 4‐bromo‐ and 4‐iodoisoquinolines reduction and coupling processes occur at the same time, leading to isoquinoline, 4,4′‐biisoquinoline and 1‐amino‐4,4′‐biisoquinoline, probably via a carbanion initially formed. Abnormal substitution was also established together with the normal AE process in the reactions of 4‐chloro‐, 4‐bromo‐ and 4‐iodo‐isoquinolines with piperidine, yielding both 1‐piperidinoisoquinoline and 4‐piperidino‐isoquinoline.
The chemistry of small ring compounds. Part 28: Cyclopropyl cation stabilisation in thermolysis of some cyclopropyl ethers and sulfides
Authors: van Tilborg W. J. M. , Steinberg H. , de Boer Th. J.
Published: September 2010

The thermolysis of 1,1′‐disubstituted dicyclopropyl ethers with substituents AcO, OH (3a); MeO, OH (3b) and HO, OH (3c) has been studied, together with the sulfide 3d, the thioether analogue of 3c. It is found that the cyclopropyl ethers 3 easily split off cyclopropanone, which cannot be isolated as such because of rapid oligomerisation. This is accompanied by some ring‐opening to a 2‐hydroxyallyl cation, CH2C(OH)\documentclass{article}\pagestyle{empty}\begin{document}$\rm{C}^\oplus $\end{document}CH2, thus explaining the ultimate formation of substituted acetones. No evidence for the transient existence of O‐protonated cyclopropanone magnified image, isomeric with the hydroxyallyl cation, could be obtained. The sulfide 3d behaves entirely differently: on heating it gives the spirocyclic sulfur compounds 12 and 13. The formation of these products is explained in terms of d‐orbital participation of sulfur in the stabilisation of an intermediate cyclo‐propylsulfinium ion.
Cycloaddition of isothiocyanates with diazomethane and hydrazoic acid
Authors: Hoff S. , Blok A. P.
Published: September 2010

Methyl, phenyl and 1‐alkenyl isothiocyanates 1 can react with diazomethane to give the corresponding 5‐amino‐1,2,3‐thiadiazoles 4. In the presence of an excess of diazomethane these thiadiazoles rearrange to 1‐substituted‐5‐(methylthio)‐1H‐1,2,3‐triazoles 3. Reaction of 1‐alkenyl isothiocyanate 1a with hydrazoic acid yields the corresponding 5‐(1‐alkenylamino)‐1,2,3,4‐thia‐triazole 11, which does not rearrange when treated with diazomethane.
Cycloaddition reactions involving carbon‐carbon double bonds of heteroaromatic compounds
Authors: Reinhoudt D. N. , Kouwenhoven C. G.
Published: September 2010

The enamine‐like character of a pyrrolidino‐substituted carbon‐carbon double bond in heteroaromatics has been demonstrated by the fact that such compounds can undergo cycloaddition reactions with 1,3‐dipolar reagents such as benzonitrile oxides, diaryl nitrilimines and electron‐deficient dienes such as 1,4‐diphenyl‐s‐tetrazine and tetrachloro‐o‐quinone. In some cases the reaction products are tautomeric mixtures of the cycloadduct and the corresponding linear (Michael) adduct. Reagents such as phenyl iso(thio)cyanate give rise to the exclusive formation of a linear Michael adduct.

The mechanisms of the reactions are discussed.
Réactivité des germylamines vis à vis de certains esters. Obtention de dérivés germaniés β‐difonctionnels
Authors: Satgé Jacques , Rivière‐Baudet Monique
Published: September 2010

The action of diethyl malonate and ethyl cyanoacetate on dimethyl(triethylgermyl)amine has been studied. In both cases, competition between two reactions is observed: a cleavage reaction of the germanium‐nitrogen bond by these reagents and an addition reaction on to the carbonyl group of an ester function.

The cleavage reaction of the Ge‐N bond leads to the corresponding β‐functional C‐germanium derivatives: ethyl C‐(triethylgermyl)malonate and ethyl C‐(triethylgermyl)cyanoacetate, thermally stable.

The addition reactions on the carbonyl group of ester functions lead to new thermally unstable β‐functional α‐aminoalkoxygermanes. These last reactions are compared with those obtained with ethyl acetate or ethylenic esters.

The thermal decomposition of β‐functional α‐aminoalkoxygermanes formed in the course of these reactions has been studied, and leads mainly to alkoxygermanes and the corresponding β‐functional amide by an intramolecular decomposition process.
Alkene exchange in chloro‐bridged platinum(II) complexes
Authors: Masters C. , Kramer P.A.
Published: September 2010

The synthesis and characterization of some chloro‐bridged platinum(II) complexes [Pt2Cl4L2], where L = 3,3‐dimethyl‐1‐butene, 3,3‐dimethyl‐1‐pentene, 3,3‐dimethyl‐1‐hexene or partially deuterated 3,3‐dimethyl‐1‐pentene is described. Complexation of these alkenes produces asymmetry within the molecule, which can be seen in the 1H NMR spectra of the complexes. The coordinated alkenes undergo exchange with free alkene in solution. The kinetics of this exchange in benzene and chloroform are reported. It has been found that alkene exchange in these complexes is preceded by a rapid dedimerization of the dimeric species.
On the mechanism of ammoxidation of propene over cerium‐doped bismuth molybdate catalysts
Authors: Giordano N. , Bart J.C.J.
Published: September 2010

The origin of the products of the ammoxidation of propene over cerium‐doped silica supported bismuth molybdates was derived from the effects of temperature (380°‐480°C) on overall conversion and selectivity in fixed‐bed operations. At low (< 80 %) conversion levels, the ammoxidation reaction leads to acrylonitrile at Mo(VI) active sites and to by‐products (HCN, acetonitrile, CO and CO2) at Mo(V) sites; at the highest conversions, by‐products derive from consecutive oxidation of acrylonitrile.
Coordination compounds containing l‐methyl‐2‐pyridone
Authors: Reedijk J. , Schrijver H. , Welleman J. A.
Published: September 2010

New compounds with the general formula M(mepydo)2+n (anion)−2 are described, where M = Mn, Co, Ni, Cu, Zn and Cd, and mepydo = 1‐methyl‐2‐pyridone; the anions being ClO−4, BF−4 and NO−3. The value of n depends upon the particular combination of cation and anion, and reaches 6 for the perchlorates and tetrafluoroborates of Cd, Mn and Ni (all octahedral cations); n can be both 6 and 4 for the perchlorates and tetrafluoroborates of Co(II) and only 4 for Zn and Cu; values for n of 2 and 3 are found for the nitrates.

Information on the structure of the compounds was obtained from infrared spectra, ligand‐field spectra and X‐ray powder diagrams. In addition, EPR spectra of Mn(II) and Cu(II) compounds and Mn doped samples of the diamagnetic compounds proved to be very useful in elucidating structures. The strenght of the metal‐ligand bond was studied further with the aid of far‐IR spectra, which showed that no metal‐oxygen vibrations occur in the region above 300 cm−1, except in the case of the copper solvates, where a band at 325 cm−1 is assigned to a Cu‐O stretch.

The ligand mepydo appears to be rather similar to the unsubstituted 2‐pyridone, although the steric effect of the methyl group has a dramatic effect upon the coordination number for the small cations, which decreases to four in the case of the Zn(II), Cu(II) and Co(II) ions, and upon the ligand‐field splitting of the Co(II) and Ni(II) ions, which decreases by more than 10% compared with unsubstituted 2‐pyridone. Moreover, the Dq value of Ni(mepydo)2+6 of 760 cm−1 is one of the lowest values sofar observed for a carbonyl group donor ligand.
1H NMR studies of σ‐adducts of pteridine and some of its derivatives in liquid ammonia
Authors: Nagel A. , van der Plas H. C. , van Veldhuizen A.
Published: September 2010

Low temperature 1H NMR spectra of pteridine dissolved in liquid ammonia, indicate that at −60°C a 1: 1 σ‐adduct is formed by addition of ammonia to the C4‐N3 bond in the pyrimidine ring and that at room temperature a stable 2:1 σ‐adduct is obtained by addition of ammonia to the pyrazine ring. The influence of substituents in the pyrimidine and in the pyrazine ring on adduct formation has been investigated. By reaction of pteridine with 15N‐labelled ammonia it was proved that no ring opening ‐ ring closure mechanism in the formation of the adducts is involved.
1H‐NMR study of the complex formation of alditols with multivalent cations in aqueous solution using praseodymium(III) nitrate as shift reagent
Authors: Kieboom A. P. G. , Spoormaker T. , Sinnema A. , van der Toorn J. M. , van Bekkum H.
Published: September 2010

Complexation of ten alditols with praseodymium(III) [isosteric with calcium(II)] as the model cation has been studied in aqueous solution by 1H‐NMR. The paramagnetic praseodymium ion shifted the resonances downfield in a regular way and allowed the identification of all the signals and the determination of the coupling constants.

The following configurational sequence of tridentate ligands (H‐COH), with respect to complex formation with PrIII has been established: xylo > threo > arabino (lyxo) > glycerol > erythro, ribo. Two major effects appear to be operative: (i) secondary hydroxyl groups show better complexation than primary hydroxyl groups; (ii) gauche butane and 1,3‐dihydroxyl repulsions introduced upon complexation cause a decrease of the complex stability.

Conformational data of both the uncomplexed and the complexed state in aqueous solution have been obtained from the vicinal coupling constants.
Conformational preference and rotational barriers in NAD+ model systems. Temperature dependence of NMR spectra for some N‐aralkylpyridinium ions
Authors: Bakker C.J. , de Gee A.J. , Verhoeven J.W. , de Boer Th. J.
Published: September 2010

In pyridinium compounds of the type X‐CH2‐CH(t‐Bu)‐Y (X,Y = substituted aryl or ‐pyridinium), hindered rotation on NMR time scale is observed for Y, even when Y does not carry ortho substituents. For X no hindered rotation is observed and furthermore, only a minor influence of meta‐ and para‐substituents in X or Y on the rotational barrier is found. The barrier appears to be mainly steric in origin and not due to charge transfer interaction. For X = p‐methoxyphenyl and Y = nicotinamidium two unequally populated rotational isomers are observed, pointing to a preferred orientation of the nicotinamidium group relative to the p‐methoxyphenyl group.
Preparation of chloroalkyl alkanedithioates and their conversion into 2‐alkylidene‐1,3‐dithiacycloalkanes
Authors: Meijer J. , Vermeer P. , Brandsma L.
Published: September 2010

Chloroalkyl alkanedithioates, R1R2CHC(S)‐S(CH2)nCl, 1 (R1, R2 = H or CH3; n = 2‐4), prepared from Grignard‐reagents R1R2CHMgX, CS2 and Cl(CH2)nBr, are treated with LiNH2 in tetrahydrofuran to form 2‐alkylidene‐1,3‐dithiacycloalkanes 3. On heating the dithioates 1 (R1, R2 = CH3; n = 1‐2) gave the corresponding 2‐alkylidene‐1,3‐dithiacycloalkanes 3. The dithioates 1 (R1, R2 = H; R1, R2 = H, CH3; n =1) cannot be converted into 3 under these circumstances 3.
Photodehydrocyclisations of stilbene‐like compounds XII. Photochemistry of 2‐(2‐benzo[c]phenanthrylethenyl)‐1,6‐methano[10]annulene
Authors: Laarhoven W.H. , Kuin N.P.J.
Published: September 2010

On irradiation of the title compound the methano group is completely eliminated. Benzo‐[m]hexahelicene is obtained as the sole cyclization product.
Oxydation des alcools. I — Choix de l'adamantanol pour déterminer la structure de l'état de transition dans l'oxydation par Cr(VI)
Authors: Durand R. , Geneste P. , Lamaty G. , Roque J.P.
Published: September 2010

The comparison of the rates of chromic oxydation of 2‐adamantanol, bicyclo[3.3.1]nonan‐9‐ol and cis and trans 4‐tert‐butylcyclohexanols shows that the transition state of this reaction is product‐like.

It appears that 1,3 diaxial interactions increase, according to the system, in the following order: cyclohexyl < adamantyl < bicyclo[3.3.1]nonane.
Approaches to analogues of anhydrogliotoxin V Syntheses of monodesthio‐secogliotoxin analogues
Authors: Ottenheijm H.C.J. , Hoffmann J.J.M.L. , Biessels P.T.M. , Potman A.D.
Published: September 2010

Two routes for the synthesis of monodesthiosecogliotoxin analogues 4 are described. The addition of suitable N‐protected α‐mercapto α‐amino acids to ethyl 3H‐indole‐2‐carboxylates followed by removal of the amino‐protecting group provides a convenient approach to the title compound. Illustrative of this, the adduct of ethyl 3,3‐dimethyl‐3H‐indole‐2‐carboxylate 8 with 2‐mercapto‐2‐(benzyloxycarbonylamido)propionic acid 11, which was prepared in situ from the mercaptoacetylated precursor 12, gave 17 after deprotection of the amino group.

A simple alternative route starts with bromination of the thiazolidinone 13 with N‐bromosuccinimide to yield 29. Substitution of the bromine with an azido group yielded the imino compound 32 directly; this could then be reduced with NaCNBH3 giving the secogliotoxin analogue 4 (RR′H).
Deazapurine derivatives XIV. The synthesis of 1‐deazaguanosine
Authors: Schelling J. E. , Salemink C. A.
Published: September 2010

A fusion reaction of 5,7‐dichloroimidazo[4,5‐b)]pyridine (2) with 1,2,3,5‐tetra‐O‐acetyl‐β‐D‐ribofuranose (3) gave, after deacetylation, 5,7‐dichloro‐3‐β‐D‐ribofuranosylimidazo[4,5‐b]pyridine (5). The site of attachment of the ribosyl moiety and the anomeric configuration of 5 were determined by converting it into 3‐β‐D‐ribofuranosylimidazo[4,5‐b]pyridine (6). In a direct condensation of 5‐acetamido‐7‐benzyloxyimidazo[4,5‐b]pyridine (7) with 2,3,5‐tri‐O‐benzoyl‐D‐ribofuranosyl chloride (8) in nitromethane, riboside 9 was formed, which afforded 1‐deazaguanosine (1) upon removal of the protecting groups. The structure of this compound was confirmed by its conversion into 5.
Reactions of hydroxycarbonium ions in strong acids VIII. Cyclization of hydroxyallyl to tetrahydrofuryl ions and related reactions
Authors: Brouwer D. M. , van Doom J. A. , Kiffen A. A.
Published: September 2010

The cyclization of hydroxyallyl ions (protonated 3‐alken‐2‐ones) to tetrahydrofuryl ions in a series of strong acids (HF, H2SO4, FSO3H) and superacids (FSO3HSbF5, HFSbF5) has been studied, together with some related reactions. The rates of cyclization of hydroxyallyl ions increase with substitution of alkyl groups at the C(5) carbon; they pass through a maximum if the acidity of the solvent is increased. It is concluded that the cyclizations involve concerted reactions, the formation of any distinct (short‐lived) intermediates taking place only when particular combinations of acidity of the solvent and structure of the starting ion are present.

Rate constants are also reported for the cis/trans isomerization of protonated 3‐penten‐2‐one. Protonated 4‐penten‐2‐one isomerizes to the hydroxyallyl ion, via solvent addition products as long‐lived intermediates, but protonated 4‐hexen‐2‐one gives the cyclized ion even under conditions of kinetic control. The acid‐catalysed ionization of protonated 5‐chloropentan‐2‐one gives a hydroxyallyl ion as the first product. All these reactions, too, involve concerted processes.
Structure analysis of the reaction products of 1′,3′,3′‐trimethylspiro[2H‐1‐benzopyran‐2,2′‐indolines] with 1,1‐bis[4‐(dimethylamino)phenyl]ethylene and related compounds
Authors: van Den Bogaert H.M. , Zwanenburg D.J. , Maas Th. A. M. M.
Published: September 2010

Reaction of 1′,3′,3′‐trimethylspiro[2H‐1‐benzopyran‐2,2′‐indolines] with 1,1‐bis[4‐(dimethylamino)phenyl]ethylene can give two types of isomeric products, 2,2‐bis[4‐(dimethylamino)‐phenyl]‐4‐{2‐methylidene‐1,3,3‐trimethylindoline}chromans (2a–e) and 1′,3′,3′‐trimethyl‐4‐{2,2‐bis[4‐(dimethylamino)phenyl]vinyl}‐spiro[chroman‐2,2′‐indolines] (3a–d).

These products and related compounds have been analysed by spectroscopic methods. The conformation of the dihydropyran ring and the chemical shift differences in the pairs of isomeric adducts are discussed.
(2 + 2)‐Cycloaddition of 9,10‐phenanthrenequinone to alkyl‐substituted aminoacetylenes. Isomerisation of the adducts via photochemical γ‐hydrogen‐abstraction and via base‐catalysis. Preparation of some phenanthro(9,10‐b]furan‐2‐one derivatives
Authors: Mosterd A. , Bos H.J.T.
Published: September 2010

Phenanthrenequinone (1) reacts with 1‐dialkylamino‐1‐alkynes 2 via (2 + 2)‐cyclo‐addition to γ‐oxo‐α,β‐unsatutrated amides 3E of the quinone methide type.

These adducts isomerise under the influence of base to α,β‐unsaturated hydroxyamides 4. Irradiation of the adducts 3E in benzene affords the same α,β‐unsaturated hydroxyamides 4 via intramolecular hydrogen‐abstraction.

Treatment of 3E with boron trifluoride gives 3‐alkyl‐3‐dialkylamino‐2,3‐dihydrophenanthro[9,10‐b]furan‐2‐ones 6 in good yields. With hydrochloric acid in acetic acid, the unsaturated hydroxyamides 4 afford 3‐alkylidene‐2,3‐dihydrophenanthro[9,10‐b]furan‐2‐ones 7. Similar reactions have been performed starting from 3,5‐di‐tert‐butyl‐o‐benzoquinone.
NMR studies on σ‐adducts of heterocyclic systems with nucleophiles (Part VII). 1H‐NMR investigations on σ‐adduct formation of pyridazine, of pyridazine 1‐oxide and some of its derivatives with ammonia. A new substitution mechanism
Authors: Klinge D. E. , van Der Plas H. C.
Published: September 2010

In the reaction of 6‐chloro‐3‐methoxy‐4‐nitropyridazine 1‐oxide with methanolic ammonia and with liquid ammonia, amino‐demethoxylation occurs. By using 1H‐NMR spectroscopy we observed that with ammonia a σ‐adduct at C(5) is formed. The unusual substitution reaction at C(3) is proposed to take place in this σ‐adduct. This new substitution mechanism is discussed.
The structure of erythromycin A cyclic carbonate
Authors: Slawinski W. , Bojarska‐Dahlig H. , Glabski T. , Dziegielewska I. , Biedrzycki M. , Naperty S.
Published: September 2010

The cyclic carbonate of erythromycin A, a compound with higher antibacterial activity than the parent antibiotic, is the 11,12‐carbonate derivative. The cyclic carbonate exhibits a hydroxy ketone/hemiacetal tautomerism in which the hemiacetal is the more stable form.
A derivative of (4‐imidazolyl)acetaldehyde of proven structure
Authors: Kivits G. A. A. , Hora J.
Published: September 2010

2‐[(4‐Imidazolyl)methyl]‐5,5‐bis(hydroxymethyl)‐1,3‐dioxane has been prepared by acetalization of (4‐imidazolyl)acetaldimide salt with pentaerythritol. The literature discrepancies on (4‐imidazolyl)acetaldehyde are discussed.
Specificity in the enzymic conversion of substituted cis‐8, cis‐11, cis‐14‐eicosatrienoic acids into prostaglandins
Authors: van Dorp D. A. , Christ E. J.
Published: September 2010

The enzyme specificity in the biosynthesis of prostaglandins has been investigated by incubation of a particulate fraction of sheep vesicular glands with substituted cis‐8,cis‐11,cis‐14‐eicosatrienoic acids. Conversions were always lower than with the unsubstituted acid (20:3). In the 2‐substituted series, a conversion of up to 50% was found for 2‐methoxycarbonyl‐ ; 2‐methyl‐ ; 2‐hydroxymethyl‐ ; 2‐butyl‐ ; 2‐methoxy‐ ; 2‐methoxymethylene‐ ; 2‐fluoro‐ ; 2‐bromo‐ ; 2‐cyano‐ ; and 2‐phenyl‐20:3. No conversion was found for 2‐hydroxycarbonyl‐ ; 2‐heptoxycarbonyl‐ ; 2‐amino‐ ; and 2‐acetamido‐20:3. In some cases, a slight preference of the enzymes for the R configuration (2‐phenyl‐ ; 2‐methyl‐20:3) was noted.

For di‐substituted acids, yields of up to 70% were found for 2‐cyano‐2‐butyl‐ ; 2,3‐cis‐ and 2,3‐trans‐methylene‐ ; 3,3‐dimethyl‐20:3, but 4,4‐dimethyl‐20:3 was not converted. However, 5‐yne‐20:3 was again a substrate (25% conversion).

Substitution at the methyl end of the precursor acid resulted in 34% conversion with 19‐methyl‐20:3, but 18‐methyl‐20:3 was not converted.

Biological activities of substituted prostaglandins were, in general, much less than those of PGE1, but for 19‐methyl‐PGE1, smooth muscle‐stimulating activity was 1.6 times that of PGE1. For some substituted prostaglandins (2‐fluoro‐ ; 2‐cyano‐PGE1), an appreciable activity in one biological test system was found but very little in others.
Synthesis of 2‐substituted cis‐8,cis‐11,cis‐14‐eicosatrienoic acids, precursors for 2‐substituted prostaglandins
Authors: van Der Linde R. , van Der Wolf L. , Pabon H. J. J. , van Dorp D. A.
Published: September 2010

Various 2‐substituted all‐cis‐8,11,14‐eicosatrienoic acids have been prepared via coupling of all‐cis‐6,9,12‐octadecatrienyl methanesulfonate with diethyl malonate, substituted diethyl malonates, ethyl cyanoacetate or ethyl 2‐cyanohexanoate. The substituents are: COOH, COOCH3, COOC4H9, COOC7H15, CH2OH, CH3, C4H9, C6H5, CH2OCH3, NHCOCH3, NH2.HCl, F, OCH3, CN and both CN and C4H9.
Reductive substitution of chlorosulfines withp‐toluenesulfinate
Authors: Veenstra G. E. , Zwanenburg B.
Published: September 2010

The reaction of chlorosulfines [R‐C(Cl)SO with R beingp‐CH3C6H4S, Cl andp‐ClC6H4] withp‐toluenesulfinate leads to products in which the CSO function is replaced by a CH2group. The first step in the reaction is a substitution of chlorine by sulfinate. Subsequent attack of the sulfinate at the sulfine sulfur atom produces sulfinyl sulfones which upon hydrolysis provide the apparent reduction products. Substantiation of the suggested reaction sequence was achieved by reaction of a sulfone sulfine with sulfinate and isolation of one of the proposed intermediates.
Copper(I) bromide promoted reaction of grignard compounds with propiolaldehyde diethyl acetal. An efficient synthesis of allenic ethers and α,β‐ethylenic aldehydes
Authors: Tadema G. , Vermeer P. , Meijer J. , Brandsma L.
Published: September 2010

Interaction between ethereal solutions of Grignard compounds RMgBr and propiolaldehyde diethyl acetal I in the presence of copper(I) bromide gives allenic ethers, III. Acid hydrolysis affords trans‐α,β‐ethylenic aldehydes, IV, in good to excellent yields.
[2 + 2] Cycloaddition reactions of heterocyclic compounds with ynamines
Authors: Reinhoudt D.N. , Kouwenhoven C.G.
Published: September 2010

Two possible routes have been investigated for the synthesis of 1‐heterocycloheptatrienes starting from annulated cyclobutene derivatives. The first approach comprised a [2 + 2 + 2] cycloreversion of tetracyclic compounds prepared from 2,3‐bis(methoxycarbonyl)‐7‐oxa‐ or −7‐azabicyclo‐[2.2.1]hepta‐2,5‐diene by a [2 + 2] cycloaddition with ynamines followed by a cycloaddition reaction with a 1,3‐dipolar reagent However, upon flash‐vacuum pyrolysis of these compounds, a retro‐1,3‐dipolar addition rather than a [2 + 2 + 2] cycloreversion occurred, yielding 2,4,6‐trimethylbenzonitrile oxide. The second approach comprised the synthesis and isomerization of [2 + 2] cycloadducts of ynamines with electron‐deficient heteroaromatics. Both 3‐nitrobenzo[b]thiophene and 4‐nitro‐isothiazole yielded [2 + 2] cycloadducts and as the by‐product nitrones. Attempts to convert the [2 + 2] cycloadducts into benzo[b]thiepins or 1,2‐thiazepines were unsuccessful.
Base‐induced ring‐opening and ring‐transformation of acetylenic epoxides and episulfides
Authors: Schreurs P. H. M. , de Jong A. J. , Brandsma L.
Published: September 2010

Epoxides magnified image, in which R can represent the groupings magnified image magnified imageare converted by KO‐t‐C4H9 in dimethyl sulfoxide into derivatives of furan or dihydrofuran and/or alcohols with the enyne system CCCCCOH. The analogous episulfides (magnified image) give, in low yield, the expected thiophene derivatives.
Kinetics of the reactions of aromatic amines and acid chlorides in hexamethylphosphoric triamide
Authors: Borkent G. , Tijssen P. A. T. , Roos J. P. , van Aartsen J. J.
Published: September 2010

The kinetics of the reaction between aromatic amines and aromatic acid chlorides in hexamethylphosphoric triamide (HMPT) have been studied by stopped‐flow spectrophotometry using an acid‐base indicator to follow the change in H⊕ during the reaction.

Measurements on bifunctional amines and acid chlorides, e.g. p‐phenylenediamine (PPD) and terephthaloyl dichloride (TDC) have shown that the NH2 groups in PPD react approximately 12 times as fast as the NH2 group in the intermediate product, while the acid chloride groups in TDC and intermediate product have equal reactivities.

It has been found for all reactions studied that protonation of the NH2 groups by the H⊕ produced is very important.

The influence of substituents could be analysed by two Hammett relations. The reaction of substituted anilines with benzoyl chloride could be described by the relation log kR = −1.4σ+R + 2.10 and the reaction of substituted benzoyl chlorides with aniline by the relation log kR = 3.4σR + 2.10.
The preparation of diribonucleoside monophosphates containing 4‐thiouridine via the phosphotriester approach
Authors: van Boom J. H. , Burgers P. M. J. , den Hartog J. , van der Marel G.
Published: September 2010

A new procedure for the synthesis of 2′‐ketals of 4‐thiouridine (1c), N4‐methylcytidine (2a) and N4,N4‐dimethylcytidine (2b), starting from the. easily accessible 3′,5′‐di‐O‐acetyl‐2′‐O‐(methoxytetrahydropyranyl)uridine (1b), has been devised. Modified dinucleoside monophosphates i6Aps4U (7a) and s4UpU (7b)

N, Y, nucleoside moiety. NpY, nucleotidyl‐(3′‐5′)‐nucleoside; s4U, 4‐thiouridine; i6A, N6‐(Δ2‐isopentenyl)adenosine. See also: Pure Appl. Chem. 40, 277 (1974).

have been prepared, in satisfactory yields, by appropriate internucleotide bond formation between (1c) and the corresponding 5′‐ester (1d) with 2′,5′‐dieO‐(methoxytetrahydropyranyl)‐N6‐(Δ2‐isopentenyl)adenosine (3) and 2′,3′‐O‐methoxymethylideneuridine (4), respectively.
On the occurrence of the SN(ANRORC) mechanism in the amination of substituted 1,3, 5‐triazines
Authors: Simig Gy. , van der Plas H. C. , Landheer C. A.
Published: September 2010

Amination of 2‐X‐4, 6‐diphenyl‐1,3,5‐triazines (X = H, Cl, SCH3) with KNH2 in liquid NH3 at −33° yields 2‐amino‐4, 6‐diphenyl‐1,3,5‐triazine. 2‐Chloro‐4, 6‐diphenyl‐1,3,5‐triazine can also be aminated by liquid NH3 at −33° to give the corresponding 2‐amino compound.

It is proved using 15N‐labelled triazines that i. the amination of 2‐(methylthio)‐4,6‐diphenyl‐1. 3,5‐triazine proceeds to the extent of about 100% by an SN (ANRORC) mechanism; ii. the amination of 2‐chloro‐4,6‐diphenyl‐1,3,5‐triazine with liquid NH3 and of 2,4‐diphenyl‐1,3,5‐triazine with KNH2 occurs by an Sn(AE) process; iii. both mechanisms occur in the amination of 2‐chloro‐4,6‐diphenyl 1,3,5‐triazine with KNH2 in liquid NH3, the ratio depending on the KNH2 concentration. PMR‐spectroscopic evidence is presented for a covalent addition of the amide ion at C‐6 of 2,4‐diphenyl 1,3,5‐triazine.
Stereochemistry of the reduction of ethyl 3,3‐dimethyl‐2,4‐dioxocyclopentanecarboxylate
Authors: Plantema O. G. , de Koning H. , Huisman H. O.
Published: September 2010

Several isomeric hydroxycyclopentanone and dihydroxycyclopentane derivatives were obtained from the reduction of ethyl 3,3‐dimethyl‐2,4‐dioxocyclopentanecarboxylate. The relative configurations of the isomers were determined by spectroscopic and chemical methods.
An SN(ANRORC) mechanism in the amination of phenyl‐1,3,5‐triazine with potassium amide in liquid ammo a A novel mechanism for the Chichibabin reaction
Authors: Simig Gy. , van der Plas H. C.
Published: September 2010

The amination of phenyl‐ 1,3,5‐triazine with potassium [15N]amide in [15N]ammonia has been investigated at −33°. It was observed that (i) a Chichibabin amination occurs at a very low rate, (ii) the amination occurs partly according to an SN(ANRORC) mechanism, (iii) a considerable amount of 15N is present in recovered starting material. All these results are explained by a series of equilibria between substrate ⇄ σ‐adducts ⇆ open‐chain amidines ⇄ product.
The discharge‐induced and the thermal reaction between methane and mixtures of bromine and chlorine
Authors: van Drumpt J.D.
Published: September 2010

As in the previously reported low‐ and high‐temperature photochemical reactions, preferred formation of CH3Br is observed when a gas mixture of the title reactants is exposed to the action of a “cold” electrical discharge (35°C) or to high temperatures (100‐450°C). The influence of the main reaction variables on product composition is discussed. It is suggested that the mechanism of CH3Br‐formation in the discharge reaction is largely analogous to that operative in the thermal and the photochemical processes. A crucial step in these reactions is the primary attack of a chlorine atom on methane. The different continous‐flow processes have approximately been optimized with respect to their CH3Br yield per pass (discharge reaction: 16%; thermal reaction: 62%). In addition, optimum energy yields with respect to CH3Br formation are compared. Of the four methods tested the high‐temperature photochemical reaction displays the most favorable combination of CH3Br yield and energy yield. The discharge method generally combines a high selectivity and energy yield with low conversions per pass, and may be attractive if recycling of reactants is possible.
Conversion of (‐)‐dihydrocodeinone into (‐)‐1‐methyldihydrocodeinone, (‐)‐1‐methyldihydrocodeine and (‐)‐1‐methyldihydrothebainone. (Chemistry of opium alkaloids, Part V)
Authors: Olieman C. , Maat L. , Beyerman H.C.
Published: September 2010

Chloromethylation of (‐)‐dihydrocodeinone (1) followed by reduction with zinc yielded, via 2, (‐)‐1‐methyldihydrocodeinone (3). Further reduction afforded (‐)‐1‐methyldihydrothebainone (4). The latter compound proved to be identical with (‐)‐1‐methyldihydrothebainone prepared by total synthesis. This proves position 1 of the chloromethylation and, in consequence, of the methyl group.

Compound 3 could also be reduced catalytically to (‐)‐1‐methyldihydrocodeine (5).
Derivatives of cis‐NPCl2(NSOCl)2 and (NPCl2)2NSOCl Part III. Butylamino derivatives of cis‐NPCl2(NSOCl)2
Authors: van Den Berg J.B. , Klei E. , de Ruiter B. , van De Grampel J.C. , Kruk C.
Published: September 2010

Reaction of cis‐NPCl2(NSOCl)2 with n‐butylamine (molar ratio 1:2) in acetonitrile leads to a mono(amino) derivative, NPCl(NHBu) (NSOCl)2. Under the same experimental conditions sec‐butylamine gives a mixture of about equal amounts of NPCl(NH‐s‐Bu) (NSOCl)2 and NPCl2NSOClNSO(NH‐s‐Bu), while tert‐butylamine yields mainly NPCl2NSOClNSO(NH‐t‐Bu). The increasing tendency towards substitution at a sulfur atom can be ascribed to an increasing steric hindrance towards the formation of an 5N1 transition state with five coordinated phosphorus. The reaction of NPCl(NHBu) (NSOCl)2 with n‐butylamine (molar ratio 1:2) gives a geminal bis(n‐butylamino) derivative, which on fluorination yields NP(NHBu)2(NSOF)2. The 31P‐ and 19F NMR spectra of the compounds prepared are discussed.
A practical technique for laboratory Birch reductions (Chemistry of opium alkaloids, Part VI)
Authors: Beyerman H.C. , van Leeuwen F.F. , Lie T.S. , Maat L. , Olieman C.
Published: September 2010

A practical technique and a simple apparatus are described, which makes possible various ways of carrying out Birch reductions on a (0.1−10 g)‐scale. Examples of reductions of 1‐benzylisoquinolines and β‐nitrostyrenes are discussed. Reaction of 1,2,3,4,5,8‐hexahydro‐1‐(3,5‐dihydroxy‐4‐methoxybenzyl)‐6‐methoxyisoquinoline (2b) with acetone yielded a hexahydrodimethylprotoberberine (3).
Réactions d'insertion 1−2,1−3 et 1−4 dans la liaison germanium‐phosphore de germaphospholannes
Authors: Couret C. , Escudié J. , Satgé J. , Redoulès G.
Published: September 2010

The 1−2 addition reactions of aldehydes on the germanium‐phosphorus bond of germaphospholanes lead to diastereoisomeric germoxyphosphepanes. An asymetric induction of the chiral phosphorus atom is observed with preferential formation of sterically favoured diastereoisomers. This stereochemistry seems to derive from a four‐centered insertion concerted mechanism. In the regio‐selective additions of conjugated ethylenic derivatives (acrylonitrile and methyl acrylate) the preferential formation of diastereoisomers is also observed. Phenylacetylene undergoes a radical insertion reaction into the intracyclic germanium‐phosphorus bond with formation of two ethylenic isomers. The reactions of germaphospholanes with cyclic ethers and α‐ethylenic aldehydes and ketones respectively lead, after 1−3 or 1−4 additions, to new germylated and phosphorylated 8 or 9 membered heterocycles. Oxidation and sulfuration reactions of germaphospholanes are also described.
Base‐induced deprotonation and ring opening of thiophene and some of its derivatives
Authors: Gräfing R. , Brandsma L.
Published: September 2010

Thiophene and its derivatives with R = H, alkyl or −SCH3 group in the 2‐ and 5‐positions (1 and 4) undergo the following types of reaction with strong bases, depending upon the nature of the base and the solvent or solvent mixture: if R = H or alkyl: abstraction of the 2‐ and 5‐proton in relatively apolar media and ring opening to enynethiolates in strongly polar media (HMPT); if R = CH3S: substitution on S in the SCH3 group by butyllithium in THF/HMPT, abstraction of a CH3S proton by butyllithium in THF (without HMPT) and ring opening in strongly polar media with LiN(i‐Pr)2.
The chemistry of small ring compounds. Part 35. Oxidation of arylcyclopropanone methyl hemiacetals by cupric ions and by oxygen
Authors: Bakker B.H. , Steinberg H. , de Boer Th. J.
Published: September 2010

Phenylcyclopropanone methyl hemiacetals 1a−c can be smoothly oxidised by a variety of oxidising agents, the nature of which exerts a strong influence on the product distribution. The common key‐intermediate in all these reactions is the ring‐opened phenyl stabilised β‐propionate radical 3 (Schemes 1 and 3). When the oxidation is carried out with cupric nitrate in pyridine the main product is meso‐ and racemic dimethyl 3,4‐diphenyladipate 4.

With cupric or ferric chloride in acetonitrile or methanol, the intermediate radicals 3a−c combine with a halogen atom in a ligand transfer reaction and afford methyl 3‐chloro‐3‐phenylpropionates 10a−c. Phenylcyclopropanone methyl hemiacetal la rapidly absorbs oxygen in the presence of a catalytic amount of cupric‐pyridine complex, giving methyl benzoylacetate 15 as the main product. Without this catalyst the absorption of one equivalent of oxygen is very sluggish and affords the methyl 3‐hydroperoxy‐3‐arylpropionate 13a. The hydroperoxide formation is notably slower in benzene than in CCl4 or CHCl3. In these chlorinated solvents, 2‐methyl‐2‐phenylcyclopropanone methyl hemiacetal 1c gives the peroxylactone 5‐methyl‐5‐phenyl‐1,2‐dioxolan‐3‐one 14.
Ring transformations in reactions of heterocyclic compounds with nucleophiles (XV) Reactions of N‐aminopyrimidinium salts with liquid ammonia
Authors: Roeterdink F. , van der Plas H.C.
Published: September 2010

N‐Aminopyrimidinium salts, e.g. 4,6‐dimethylpyrimidinium (2a), 4,6‐diphenylpyrimidinium (2b) and 2,4,6‐trimethylpyrimidinium mesitylenesulfonates (2c), show a very divergent behaviour towards liquid ammonia at − 33°. 1) Proton abstraction takes place from the amino group of 2a, resulting in the formation of a 1,3‐dipolar intermediate, which under the reaction conditions dimerises. 2) Adduct formation is observed on C(2) of 2a or C(6) of 2c, resulting in the formation of a pyrazole or a 1,2,4‐triazole ring. 3) Deamination occurs with 2b and 2c, via two pathways, namely, a nucleophilic attack of ammonia on the nitrogen atom of the amino group or by a ring opening/ring closure sequence. This last‐mentioned mechanism has been proved by use of 15N‐labelled ammonia.
Electronic and e.s.r. spectra of compounds containing the tetrakisdithiocarbamato‐molybdenum(V) or ‐tungsten(V) cations
Authors: Nieuwpoort A. , Steggerda J.J.
Published: September 2010

Electronic spectra and e.s.r. spectra of the compounds [M(R2dtc)4]X (M = Mo, W; R2dtc = R2NCS2−; R = Me, Et, i‐Pr, Ph, Bz; R2 = Tm, Pm, MeBz; Tm = (CH2)4; Pm = (CH2)5; X = halide) have been investigated. In the electronic spectra d‐d transitions, electron‐transfer bands, and internal ligand absorptions could be assigned. The d‐d transitions are fitted into the Ligand‐Field model, yielding for Mo(V): Dq = 2.95 kK, Cp = 0 kK, and λ = 460 cm−1, and for W(V): Dq = 3.38 kK, Cp = 0 kK, and λ = 1610 cm−1. The e.s.r. spectra show a very small g anisotropy. This cannot be fitted into the Ligand Field model, due to spin‐orbit coupling on the coordinated sulfur atoms. An Extended Hückel MO calculation for the molybdenum complex shows that 86% of the unpaired electron is in the metal xy orbital. The experimental g values show fair agreement with the results of the MO calculations.
Vinyl copper(I) compounds Part I: Stereospecific addition of heterocuprates to 1‐alkynes in tetrahydrofuran
Authors: Westmijze H. , Meijer J. , Bos H.J.T. , Vermeer P.
Published: September 2010

In this paper a study on the reactivity of various heterocuprates [RCuY]MgX 1 towards 1‐alkynes R′−C≡CH 2 in tetrahydrofuran is presented. In most cases a smooth cis addition was observed in this solvent generally leading, after protic work‐up, to terminal alkenes RR′CCH2 4a or sometimes to mixtures of alkenes 4a and non‐terminal E‐alkenes R′CHCHR 4b in excellent yields. Except for the reaction of [t‐BuCuBr]MgCl with Ph−C≡C−H no evidence was obtained of proton abstraction from the terminal alkynes 2 by the cuprates.

The influence of CuBr and LiBr on the course of the addition reaction was studied in some cases.
Cyclohexaamylose modified with an oxime group: An enzyme model
Authors: van Hooidonk C. , de Korte D. C. , Meereboer M. A. C. Reuland
Published: September 2010

A three‐step synthesis was utilized to introduce the nucleophilic oxime group, 2(hydroxyimino)ethyl, into cyclohexaamylose (CHA) at the 2‐O or 3‐O position. The rates of deacylation of p‐nitrophenyl acetate (PNPA) in aqueous solutions were determined without and in the presence of varying concentrations of O‐[2‐(hydroxyimino)ethyl]‐CHA (CHA‐Ox). From the observed Michaelis‐Menten‐like kinetics, the pH dependence and competitive inhibition experiments with cyclohexanol it was concluded that the deacylation is consistent with a reaction scheme involving a 1: 1 inclusion complex followed by a rate‐determining nucleophilic displacement of the p‐nitrophenoxide ion by the ionized oxime group.

The CHA‐Ox cavity provides an effective binding site for PNPA resulting in a favourable orientation of the acyl residue with respect to the oxime group. The rate accelerations can be ascribed to an apparent increase in the local concentration of the reactive species. CHA‐Ox displays substrate specificity illustrated by using m‐nitrophenyl acetate and p‐nitrophenyl dimethylphosphinate as substrates.

The CHA‐Ox/ester system represents a model for the acylation of hydrolytic enzymes.