bluuebunny/crossref_metadata_2025 huggingface dataset:
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

On 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

It 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

The 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

The 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

A 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

The 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

When 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

The 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

The 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

The 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.
Proton chemical shifts of carbanions and distribution of charge calculated by the ω‐technique
Authors: Kloosterziel H.
Published: September 2010

A close relation exists between experimental proton chemical shifts of carbanions and π‐electron densities as calculated by the ω‐technique. The proportionality factor for phenyl protons is 20 ppm per unit charge.
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

Large‐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

Amination 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

On 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

It 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.
Synthèse et propriétés physico‐chimiques de trois chloro‐10 tétraméthylphénoxarsines
Authors: Saint‐Ruf G. , Clément M. , Coïc J. P.
Published: September 2010

10‐chloro‐2,3,7,8‐tetramethyl‐, 10‐chloro‐2,4,6,8‐tetramethyl‐ and 10‐chloro‐3,4,6,7‐tetramethylphenoxarsines were prepared; the chemical shifts of the protons of these new compounds and those of 10‐chlorophenoxarsine in N.M.R. spectra are reported, as well as the fragmentation patterns noted in their mass spectra.
Excess mixed anhydride peptide synthesis with histidine derivatives
Authors: Beyerman H. C. , Hirt J. , Kranenburg P. , Syrier J. L. M. , van Zon A.
Published: September 2010

The coupling of histidine derivatives by the excess mixed anhydride method was investigated with respect to the yield, the racemization, and the formation of by‐products. The tert‐butyloxycarbonyl‐ (Boc‐), isobutyloxycarbonyl‐ (i‐Boc‐), benzyloxycarbonyl‐ (Z‐), and p‐toluenesulfonyl‐(Tos‐) groups were found to be suitable for protection of the imidazole nucleus.

A new way of selective removal of the Nim‐Tos group, with pyridine hydrochloride, is described.
Thermal rearrangements of divinyl disulfides
Authors: Larsson F. C. V. , Brandsma L. , Lawesson S.‐O.
Published: September 2010

Divinyl disulfides, obtained by oxidative coupling of anions derived from dithioesters with iodine, have been rearranged to bisdithio esters; these have been converted to derivatives of thiophene by simple heating and by treatment with bases followed by alkylation. Starting from methyl dithiopropionate and methyl phenyldithioacetate these operations led to 2,5‐bis(methylthio)‐3,4‐dimethylthiophene, 2,5‐bis(methylthio)‐3,4‐diphenylthiophene and 2‐mercapto‐5‐(methylthio)‐3,4‐diphenylthiophene, respectively. The divinyl disulfide, obtained from methyl dithioisobutyrate did not undergo thermal rearrangement at elevated temperature.
Ring opening and ring contraction in reactions of some aminobromo‐ and dibromoisoquinolines with potassium amide in liquid ammonia
Authors: Sanders Georgine M. , van Dijk M. , den Hertog H. J.
Published: September 2010

Reactions of some aminobromo‐ and dibromoisoquinolines with KNH2 in liquid NH3 have been investigated. Compounds with an amino group and a bromo atom in positions α to the heteroatom, show a very fast ring opening, leading to o‐cyanobenzyl cyanide. The 1,4‐substituted aminobromoisoquinolines do not react; 4‐amino‐3‐bromoisoquinoline undergoes ring opening into o‐cyanobenzyl isocyanide, 3‐amino‐4‐bromoisoquinoline ring contraction to 1‐cyanoisoindole. The dibromoisoquinolines react primarily by nucleophilic substitution.
Conformation of non‐aromatic ring compounds ‐ 89 The conformation of 3‐(2,6‐dichlorophenyl)glutaric anhydride studied by dynamic proton magnetic resonance and empirical force field calculations
Authors: Koer F. J. , Faber D. H. , Altona C.
Published: September 2010

The dipole moment and PMR spectra of 3‐(2,6‐dichlorophenyl)glutaric anhydride were measured and interpreted in terms of conformational properties of the anhydride ring and its side chain. Equilibrium compositions in several solvents are derived from vicinal proton couplings. The 2,6‐dichlorophenyl group prefers the equatorial position over the axial one to the extent of 2.1 kcal/mol with a strong rotational preference for the parallel conformational (Epl: Ph//3H). Broadening and collapse of the PMR spectra in the aromatic hydrogen region on lowering the temperature indicates the existence of an appreciable barrier opposing rotation about the sp2‐sp3 carbon‐carbon bond. A full line‐shape analysis gives the activation energy; ΔG≠298: 13.4 ± 0.2 kcal/mol (acetone‐d6) and 13.5 ± 0.2 kcal/mol (dichloromethane‐d2). These values accord well with the barrier height obtained from empirical force field calculations, 14.5 kcal/mol. The transition state is predicted to correspond to the Epr conformation (Ph ± 3H).
Rational synthesis of 4‐hydroxy‐2,5‐dimethyl‐3‐[2H]‐furanone and keto‐enol equilibria of diketone intermediates
Authors: van den Ouweland G. A. M. , Tjan S. B.
Published: September 2010

4‐Hydroxy‐2,5‐dimethyl‐3‐[2H]‐furanone was prepared in an overall yield of 40% via a new route from acetone and ethyl lactate. The percentages of the enol‐keto tautomers of a number of intermediate 2,4‐diketones have been determined by PMR analyses.
Insertion of phenyl isocyanide into ethanol catalysed simultaneously by copper(I) and base
Authors: Knol D. , van Os C. P. A. , Drenth W.
Published: September 2010

The insertion of phenyl isocyanide into ethanol under the influence of base and Cu(PhNC)4BF4 is investigated mechanistically. In pre‐equilibria the BF4⊖ anion is exchanged for ⊖OC2H5. By intramolecular nucleophilic attack of ⊖OC2H5 on coordinated isocyanide an [(ethoxy)‐(phenylimino)methyl]copper intermediate is formed. The substituent effect supports this conclusion. In a rapid reaction with ethanol the intermediate decomposes and the insertion product, ethyl N‐phenylformimidate, is formed. It reacts slowly to give N,N′‐diphenylformamidine, which is precipitated at the end of the reaction as a copper complex.
[3,3]‐Sigmatropic rearrangement of 1‐alkenyl allenyl sulfides. Synthesis of γ,δ‐acetylenic aldehydes and ketones
Authors: Brandsma L. , Verkruijsse H. D.
Published: September 2010

Thermal rearrangement of the sulfides magnified image (R1 ‐ R4 is H or alkyl) at 125−135° in a mixture of dimethyl sulfoxide and water gives, γ,δ‐acetylenic aldehydes (R3 = H) or ketones (R3 = alkyl) magnified image in moderate yields.
The chemistry of small ring compounds. Part 29: Synthesis and stereochemistry of some arylcyclopropanone methyl hemiacetals and their acetates
Authors: Bakker B. H. , Steinberg H. , de Boer Th. J.
Published: September 2010

Some mono‐aryl substituted 1‐methoxycyclopropanols (cyclopropanone hemiacetals) with the following aryl groups, C6H5‐, p‐CH3C6H4‐ and p‐ClC6H4‐, have been prepared in 80‐85 % yield by passing ketene at −70°C into a solution of aryldiazomethane in CFCl3 or CCl4, containing an excess of methanol, which adds to the intermediate arylcyclopropanone. It appears that the addition of methanol to the carbonyl group in the arylcyclopropanone takes place preferentially at the least hindered side of the cyclopropyl ring as is shown by structure elucidation (NMR) of the more stable acetates derived from the hemiacetals.
A novel method for the synthesis of specifically substituted cycloheptatrienes
Authors: van Tilborg W.J.M. , Smael P. , Visser J.P. , Kouwenhoven C.G. , Reinhoudt D.N.
Published: September 2010

A novel method has been developed for the synthesis of substituted cycloheptatrienes, involving the cycloaddition of substituted cyclopropenes to substituted thiophene 1,1‐dioxides followed by expulsion of sulfur dioxide from the cycloadduct. The scope and limitations of the reaction have been investigated and its mechanism is discussed. Attempts to extend this reaction principle to the synthesis of 1‐heterocycloheptatrienes were unsuccessful.
Formation of new ring systems by addition of hydrogen sulfide, selenide, telluride, water and primary amines to cyclohexyl‐ or phenyl‐ di(1‐alkynyl)phosphine oxides and alkyl di(1‐alkynyl)phosphinates under nucleophilic conditions
Authors: Naaktgeboren A. , Meijer J. , Vermeer P. , Brandsma L.
Published: September 2010

Interaction between di‐1‐alkynylphosphine oxides or di‐1‐alkynylphosphinates and disodium disulfide, sodium selenide, sodium telluride, water and primary amines in solvents like water, methanol, dimethylformamide, liquid ammonia gives the new six‐membered heterocyclic systems 2–6.
Aromatic lead(IV) compounds VII. The plumbylation of aromatic compounds
Authors: de Vos D. , van Barneveld W.A.A. , van Beelen D.C. , van Der Kooi H.O. , Wolters J. , van Der Gen A.
Published: September 2010

The plumbylation of a large number of aromatic compounds is reported and a route for the preparation of the novel compounds ArAr′PbX2 is described. The course of the plumbylation reaction is discussed and its selectivity is explained in terms of differences in reactivity of aryllead(IV) compounds with halogen substituted acetic acids.
Approaches to analogues of anhydrogliotoxin IV Syntheses and reactions of 2‐mercapto‐2‐aminopropionic acid derivatives
Authors: Ottenheijm H.C.J. , Potman A.D. , van Vroonhoven T.
Published: September 2010

Several S,N‐protected‐2‐mercapto‐2‐aminopropionic acid derivatives (3a‐g Table I) have been prepared by the reaction of thiols with the corresponding N‐protected 2‐hydroxy‐2‐amino‐propionic acid derivatives 8, prepared from the corresponding amides 7 and pyruvic acid. Recent controversies in the literature regarding this method are discussed. Selective removal of the sulfur‐protecting group in 3b and 3e afforded the 2‐mercapto‐2‐acylamidopropionic acids 11, R2 = H and C6H5 respectively. Reaction of 3e with thionyl chloride afforded 4‐methyl‐4‐(acetylthio)‐2‐phenyl‐2‐oxazolin‐5‐one 10. Under these conditions 3g gave the Leuchs' anhydride 14.
Stereoselectivity and proton binding in some transition‐metal complexes of N‐(o‐hydroxybenzyl)alanine
Authors: Ritsma J. H.
Published: September 2010

Stability constants and stereoselective effects are presented for some transition‐metal complexes of the new legand, N‐(o‐hydroxybenzyl)alanine, H2(oHBAl). The preparation of DLH2(oHBAl) and optically pure LH2(oHBAl), by hydrogenation of the salicylaldimine of alanine, is described. The M‐oHBAl systems studied are complicated by the presence of protonated species [M = Co(II), Ni(II), Cu(II) and Zn(II)] or a hydroxylated species [M = Zn(II)]. From comparison of competition constants it is concluded that the proton in the protonated complexes is bound to the phenoxy atom (CoHA2, NiHA2, NiHA and CuHA) or, possibly, to the secondary nitrogen atom (CuHA2, ZnHA2) of (oHBAl)2−, A. Appreciable stereoselective effects, in favour of the “racemic complex” {M(LA)2 + M(DA)2}, are found for the cobalt and nickel bis‐complexes. In the copper bis‐complexes no stereoselectivity was found.
A 15N‐study of the conversion of 3‐(methylthio)‐1,2,4‐triazine with potassium amide in liquid ammonia at ‐ 75°C
Authors: Rykowski A. , van der Plas H. C.
Published: September 2010

Treatment of 3‐(methylthio)‐1,2,4‐triazine with potassium amide in liquid ammonia gives 3‐amino‐1,2,4‐triazine, 3,3′‐bis(methylthio)‐5,5′‐bi‐1,2,4‐triazine and 3‐amino‐3′‐(methylthio)‐5,5′‐bi‐1,2,4‐triazine. In the 3‐amino compound formed from 3‐(methylthio)‐[4‐15N]‐1,2,4‐triazine, 93% of the 15N is present in the exocyclic nitrogen of the amino group. A SN(ANRORC) mechanism is proposed for this amino‐de(methylthio)lation reaction.
A 13C‐NMR study of squalene some aspects of the selective terminal oxidation of squalene
Authors: van Dommelen Marianne E. , Wilson Arnold R. N. , de Haan Jan W. , Buck Henk M.
Published: September 2010

13CNMR data (shifts and relaxation times) show that the conformational equilibrium and the intramolecular mobility of squalene are very similar in media of different polarity. This is inconsistent with one of van Tamelen's original proposals explaining the selective terminal epoxidation in terms of tight coiling of squalene in polar media. MINDO/2′ calculations predict that terminal epoxidation is favoured over internal epoxidation by ∼1.5 kcal/mole.
Synthesis of substituted cis‐8,cis‐11,cis‐14‐eicosatrienoic acids, precursors of correspondingly substituted prostaglandins
Authors: Heslinga L. , van Der Linde R. , Pabon H. J. J. , van Dorp D. A.
Published: September 2010

The synthesis of the following groups of acids is described: (a) 3‐Methyl‐c‐2,c‐8,c‐11,c‐14‐, and 3‐methyl‐t‐2,c‐8,c‐11,c‐14‐eicosatetraenoic acid and 3‐methyl‐c‐8,c‐11,c‐14‐eicosatrienoic acid, (b) c‐8,c‐11,c‐14‐eicosatrien‐5‐ynoic acid, (c) c‐2,3‐methylene‐,t‐2,3‐methylene‐,3,3‐dimethyl‐ and 4,4‐dimethyl‐c‐8,c‐11,c‐14‐eicosatrienoic acid, (d) 18‐methyl‐, (S)‐18‐methyl‐ and 19‐methyl‐c‐8,c‐11,c‐14‐eicosatrienoic acid. They were obtained via coupling of (a) c‐7,c‐10,c‐13‐nonadecatrien‐2‐one with ethoxycarbonylmethylenetriphenylphosphorane and c‐7,c‐10,c‐13‐nonadecatrien‐2‐yl methane sulfonate with diethyl malonate, (b) l‐bromo‐c‐2,c‐5,c‐8‐tetradecatriene with 5‐hexynoic acid, (c) 1‐bromo‐2,5‐undecadiyne with the appropriately substituted 8‐nonynoic acids and (d) from the correspondingly substituted 1‐bromo pentanes, using standard procedures.
Proton bonding to 1,8‐bis(dialkylamino)naphthalenes
Authors: de Groot R. L. , Sikkema D. J.
Published: September 2010

Proton NMR spectra of 1,8‐bis(dimethylamino)naphthalene and 1,8‐bis(diethylamino)‐naphthalene (MPS and EPS) solutions to which acetic acid or trifluoroacetic acid (TFA) has been added exhibit several characteristic features caused by proton exchange phenomena. In the presence of less than one mole of TFA per mole of diamine the protonated and unprotonated forms can be observed separately. The proton in the protonated amine resonates at unusually low field (∼20 ppm). When more TFA is added another proton signal at low field, between 18 and 12 ppm down field from TMS, is observed. The nature of the latter proton resonance is discussed. The proton in the amine is probably in a bridge between the two nitrogen atoms, since no magnetic inequivalence is observed for the four methyl or ethyl groups attached to the nitrogen. In the presence of acetic acid instead of TFA the proton in the amine molecule changes places with the other protons in the solution. From the temperature‐dependence of the spectra the activation energy for the exchange of D+ between amine molecules has been estimated. The possible use of MPS as a probe for the investigation of hydrogen bonding phenomena in carboxylic acid solutions in non‐aqueous solvents is indicated.
Didehydrohetarenes (XXXVII). On the existence of 4,5‐didehydropyridazine
Authors: Klinge D.E. , van der Plas H.C.
Published: September 2010

Reaction of 4‐chloro‐3,6‐diphenylpyridazine with potassium amide in liquid ammonia gives 4‐amino‐3,6‐diphenylpyridazine and imino‐4,4′‐bis(3,6‐diphenylpyridazine). Starting with 4‐chloro‐3,6‐diphenylpyridazine‐[5‐13C], it was proved by quantitative 13CNMR measurements that both products are formed via the intermediacy of 4,5‐didehydro‐3,6‐diphenylpyridazine.
The synthesis of bis‐endo‐2‐(hydroxymethyl)‐5‐(4‐imidazolylmethyl)‐bicyclo[2.2.2]octane and the corresponding cyclohexane analogue
Authors: Hora J.
Published: September 2010

A synthesis of bis‐endo‐2‐(hydroxymethyl)‐5‐(4‐imidazolylmethyl)bicyclo [2.22]octane and cis‐1‐(hydroxymethyl)‐4‐(4‐imidazolylmethyl)cyclohexane is reported. Two sequences of reactions representing the formal replacement of halogen by the 4‐imidazolyl group have been developed.
The addition of hydrogen bromide to syn‐7‐methoxybicyclo[2.2.1]hept‐2‐ene
Authors: Boerhorst E. , Klumpp G.W.
Published: September 2010

Free radical addition of hydrogen bromide to syn‐7‐methoxybicyclo[2.2.1]hept‐2‐ene (1) yields mixtures of exo‐ and endo‐2‐bromo‐syn‐7‐methoxybicyclo[2.2.1]heptanes (2 and 3). Under ionic conditions products of skeletal rearrangements (4 and 5) are formed besides 2. No indications of 4‐MeO participation were found.
Esters β‐thiocétoniques cyclaniques N° 3 Thio‐réarrangement de Claisen
Authors: Morin L. , Paquer D. , Smadja S.
Published: September 2010

Alicyclic β‐thioxo esters react with alkyl halides and ethyl chloroacetate to give S‐alkylated compounds.

Thioclaisen rearrangement is observed with allyl bromide, crotyl bromide, and propargyl bromide.
Chemistry of sulfines. Part 32. Synthesis and reactions of (phenylsulfonyl)ketene dimethyl dithioacetal monoxide
Authors: Veenstra G.E. , Zwanenburg B.
Published: September 2010

Oxidation of methyl (phenylsulfonyl)dithioacetate (1) with m‐chloroperbenzoic acid gave the sulfine C6H5SO2CH2C(SO)SCH3 (2).

Deprotonation of 2 with TlOEt and subsequent S‐alkylation of the thallium(I) salt with methyl iodide gave (phenylsulfonyl)ketene dimethyl dithioacetal moxonide (5). When other bases were used in the deprotonation step deoxygenated products, viz. C6H5SO2CHC(SCH3)2 were obtained. Evidence is presented that oxygen is lost by an intramolecular redox reaction of an initially formed vinylsulfenic ester.

The new ketene dithioacetal monoxide 5 reacts with malonate anions in an additon‐elimination reaction in which the phenylsulfonyl group serves as the leaving group.
Magnetic measurements, electron spin resonance and far‐infrared spectra of manganese(II) urea compounds
Authors: Barbier J.P. , Hugel R.P. , van Der Put P.J. , Reedijk J.
Published: September 2010

Compounds Mn(ur)n(anion)2 [ur is urea (U), N,N′‐dimethylurea (DMU) and N,N′‐diethylurea (DEU), n = 2, 3, 4, 6, 10, and anion = Cl−, Br−, I− and ClO−4] have been studied by ESR, far‐IR and low‐temperature magnetic susceptibility. With U as the ligand, anion = Cl, Br and n = 2 halogen‐bridged linear‐chain compounds are formed, with oxygen‐bonded U in the axial positions. The Mn atoms in the chain are antiferromagnetically coupled with J/K values of −0.6 K (Br) and −1.0 K (Cl).

Compounds Mn(U)4X2 appear to be tetragonally coordinated with the anions in the axial positions. The zero‐field splittings of the ground state have been determined as 0.11 and 0.18 cm−1 for X = Cl and Br, respectively. The octahedral cations Mn(ur)2+6 have been studied by ESR and far‐IR spectra, and were found to be barely distorted. Mn‐O vibrations occur in the 200‐235 cm−1 region. Compounds with n = 3 found for ur = DEU should be described as Mn(DEU)6MnX4 (X = Cl, Br). A new type of compound (n = 3; ur = DMU; X = Cl, Br, I) all of which are nearly isomorphous, is believed to be monomeric and contains two kinds of DMU ligands.
Addition of oxygen nucleophiles to alkyldicyanamides
Authors: Benders P.H.
Published: September 2010

Oxygen nucleophiles such as water, alcohols and phenols, have been reacted with alkyldicyanamides (1). Selective addition to one of the cyano groups only was effected by a careful control of the reaction conditions. The reactions have been employed for the synthesis of a number of novel 1‐alkyl‐1‐cyanoureas (2), 1,2‐dialkyl‐1‐cyanoisoureas (5) and 1‐alkyl‐2‐aryl‐1‐cyanoisoureas (7). The reactivity of the cyano group in 1 has been explained in terms of a relatively “soft” electrophilic carbon atom. Proof of structure for the novel compounds was obtained by chemical transformations and with the help of IR and PMR spectroscopy.
Effect of the ensemble size in the hydrogenation of benzene on Pt and Pt‐Au catalysts
Authors: Puddu S. , Ponec V.
Published: September 2010

Hydrogenation of benzene and cyclohexene has been studied on Pt and four Pt‐Au alloys. The overall behaviour −‐ activity, selfpoisoning and regeneration was similar to that of Ni−Cu alloys. The surface of the two‐phase Pt−Au alloys had, according to the kinetic data a composition of the β‐alloy (Au‐rich phase). Hydrogenation of benzene was 103 to 104 times slower than the hydrogenation of cyclohexene. The most dilute alloys are active in cyclohexene hydrogenation but they are completely inactive in the low temperature hydrogenation of benzene. The main effect of alloying is the decrease in the pre‐exponential term of the rate. The effect is explained in geometric terms: activation of a benzene molecule for the low temperature hydrogenation requires larger ensembles than those for cyclohexene activation and the larger ensembles are missing on the surface of the most dilute alloys.
Chemistry of crown ethers: Synthesis of crown ethers derived from α,γ‐and α,δ‐bis(halomethyl)‐ or α,γ‐bis(hydroxymethyl)‐substituted aromatics
Authors: Gray R.T. , Reinhoudt D.N. , Smit C.J. , Veenstra I.
Published: September 2010

Three series of novel crown ethers have been prepared in which polyether rings of various sizes are linked to a benzene ring through the 1,3‐ or 1,4‐positions or to a furan ring through the 2,5‐positions. They were synthesized from the corresponding α,γ‐ or α,δ‐bis(halomethyl)‐substituted aromatics by reaction with polyethylene glycol disalts or from the disalts of bis(hydroxymethyl)‐substituted aromatics by reaction with polyethylene glycol ditosylates. Both 1:1 (2−67 % yield) and 2:2 (6−30% yield) cyclic reaction products were formed.

The fact that the above compounds, which may contain up to 31 ring atoms, are obtained in such high yields without operating at high dilution is connected with the relationship between the chain length of the polyethylene glycol and the diameter of the cation used in the synthesis (template effect).
Studies on polypeptides XVIII Solid‐phase synthesis of RNase S‐peptide analogues with high S‐protein activating ability; replacement of histidine‐12 by L‐homohistidine
Authors: van Batenburg O.D. , Raap J. , Kerling K.E.T. , Havinga E.
Published: September 2010

As part of a structure‐activity relationship study of ribonuclease, focussing on the role of histidine‐12 in the active centre, the following polypeptides have been synthesized by the solid‐phase method and tested for S‐protein activating ability: bovine RNase S‐peptide 1−14, [Ile13]‐ S‐peptide 1−14 and the corresponding analogues in which histidine‐12 is replaced by L‐homohistidine. Whereas their binding tendency is considerably lower the [Hhi12] analogues show a remarkably high ability to generate enzymatic activity when combined with S‐protein in the presence of yeast RNA as a substrate.
Electronic spectra and magnetic susceptibilities of some eight‐coordinated complexes of molybdenum(IV) and tungsten(IV)
Authors: Nieuwpoort A. , Steggerda J.J.
Published: September 2010

The electronic spectra and magnetic susceptibilities of some complexes of the type Mo(R2dtc)4 (R2dtc = R2NCS2−; R = Me, Et, i‐Pr, Ph; R2 = Tm, Pm, MeBz; Tm = (CH2)4; Pm = (CH2)5) and M(Rdta)4 (M = Mo, W; Rdta = RCS2−; R = Tol, Naf; Tol = p‐toluoyl, Naf = 2‐naphthoyl) are reported. In contrast to literature data, the R2dtc complexes are diamagnetic, like the Rdta compounds. This is in agreement with a Ligand Field calculation for this type of compound, which shows, that for a moderate reduction in the electronic repulsion parameter B, diamagnetic behaviour is to be expected.

Extended Hückel calculations show that the lowest unoccupied MO in Mo(Rdta)4 has ligand character, in contrast to Mo(R2dtc)4. This is in agreement with the charge‐transfer character of the absorption near 12 kK found in the electronic spectra of Mo(Rdta)4, while the Mo(R2dtc)4 compounds show a d‐d absorption at 10.8 kK.
On the N‐ethylation of 4‐alkoxy‐ and 4,6‐dialkoxypyrimidines with triethyloxonium tetrafluoroborate
Authors: Oostveen E. A. , van der Plas H. C.
Published: September 2010

Reaction of 4‐alkoxy‐(1–4) or 4,6‐dialkoxypyrimidines (5–9) with 1 equivalent of triethyloxonium tetrafluoroborate yields 4‐alkoxy‐N‐ethyl (13–15) or 4,6‐dialkoxy‐N‐ethylpyrimidinium salts (10–12), respectively. With two or more equivalents of this reagent, rearrangement of N‐ethylalkoxypyrimidinium salts into 1‐ethyl‐3‐alkyl‐1,4(3,4)‐dihydro‐4‐oxopyrimidinium salts (16–22) takes place. These rearrangements can also be performed by heating. The mechanism of these rearrangement reactions is discussed.
Ring transformations of heterocyclic compounds with nucleophiles. Part XVI. Degenerate ring transformations of 1,3‐diethyl‐1,4(3,4)‐dihydro‐4‐oxopyrimidinium tetrafluoroborates with ammonia
Authors: Oostveen E. A. , van der Plas H. C.
Published: September 2010

Treatment of 1,3‐diethyl‐1,4(3,4)‐dihydro‐4‐oxopyrimidinium tetrafluoroborate and its 2‐phenyl, 6‐phenyl, 6‐methyl and 6‐ethoxy derivatives with aqueous ammonia resulted in the formation of a mixture of open‐chain compounds i.e. N‐formyl(acetyl,benzoyl)‐N‐ethyl‐3‐(ethylamino)‐acrylamides and N‐ethyl‐3‐[formyl(acetyl,benzoyl)ethylamino]‐acrylamides. They are formed by cleavage of the pyrimidine ring between the N(1)‐C(2) and N(3)‐C(2) bond, respectively. In liquid ammonia the same ring cleavage generally occurs; however, in the case where a 6‐ethoxy group is present, recyclisation can take place, leading to 6‐(ethylamino)pyrimidine derivatives. This degenerate ring transformation has been observed also with the 2‐methyl and 2‐phenyl derivative of 1,3‐diethyl‐1,4(3,4)‐dihydro‐6‐ethoxy‐4‐oxopyrimidinium tetrafluoroborate. Evidence is presented by means of 1H‐NMR and 13C‐NMR spectroscopy that all these reactions are iniated by attack of NH3 at the C(2)‐position. Some of the above‐mentioned open‐chain compounds underwent a ring closure to the initially used 1,3‐diethyl‐1,4(3,4)‐dihydro‐4‐oxopyrimidinium tetrafluoroborates on treating them with hydrofluoroboric acid in absolute ethanol.
ESR investigation of the radical intermediates formed in the photoreduction of azo dyes
Authors: Heijkoop G. , van Beek H. C. A.
Published: September 2010

ESR‐spectra of hydrazyl and aminonaphthoxy radicals formed upon photoreduction of azo dyes have been measured. For the hydrazyl radicals the results obtained further confirm previous investigations of the mechanism of photoreduction of azo dyes. The direct identification in photo‐reduced dye solutions of aminonaphthoxy radicals, which are formed in the oxidation reduction equilibrium of aminonaphthols and iminoquinones provides strong evidence for previously proposed mechanisms for the disproportionation of hydrazyl radicals
Thermal addition of tosyl cyanide to norbornadiene. A Homo‐Diels‐Alder cycloaddition versus homo‐conjugate 1,4‐addition
Authors: Jagt J. C. , van Leusen A. M.
Published: September 2010

Tosyl cyanide reacts smoothly with norbornadiene to form a nortricyclene‐derived tetracyclic lactam (4) by a [2 + 2 + 2]‐cycloaddition (Homo‐Diels‐Alder reaction), and two other nortricyclene derivatives by homo‐conjugate 1,4‐addition reactions. The structure and stereochemistry of the reaction products 4, 5 and 6 are fully elucidated by 1H and 13C NMR spectroscopy.
Vinylcopper(I) compounds: Part III: Direct conversion of 1‐alkenylcuprates into stereospecifically substituted 1‐halogeno‐1‐alkenes
Authors: Westmijze H. , Meijer J. , Vermeer P.
Published: September 2010

Halogenation of vinylcopper(I) compounds [RR′CCHCu(Br or R)]MgX, prepared stereospecifically bycis‐addition of [RCuBr]MgX or [R2Cu]MgX to 1‐alkynes R′‐C≡CH in tetrahydrofuran, with one of the halogenating reagentsN‐chlorosuccinimide,N‐bromosuccinimide, BrCN, ICN or I2, leads in high yields to the corresponding 1‐halogeno‐1‐alkenes RR′CCHX (X = Cl, Br or I). The introduction of the halogen atom occurs with retention of configuration (ciswith respect to R).
Electrocyclic opening of benzol [b]thiophene
Authors: Beyer A.E.M. , Kloosterziel H.
Published: September 2010

Reacting the title compound with lithium dimethylamide and subsequent addition of methyl iodide yields E‐β‐(dimethylamino)‐o‐(methylthio)styrene.
The crystal and molecular structures of 4,6‐diethoxy‐1‐ethylpyrimidinium tetrafluoroborate and 6‐ethoxy‐1,3‐diethyl‐1,4(3,4)‐dihydro‐4‐oxopyrimidinium tetrafluoroborate, two isomeric reaction products of 4,6‐diethoxypyrimidine with Meerwein reagent
Authors: Heijdenrijk D. , Stam C.H. , Oostveen E.A. , van der Plas H.C.
Published: September 2010

The crystal and molecular structures of two isomeric compounds, 4,6‐diethoxy‐1‐ethylpyrimidinium tetrafluoroborate and 6‐ethoxy‐1,3‐diethyl‐1,4(3,4)‐dihydro‐4‐oxopyrimidinium tetrafluoroborate, reaction products of 4,6‐diethoxypyrimidine with Meerwein reagent [O(C2H5)+3 BF−4], have been determined by means of X‐ray diffraction.

4,6‐Diethoxy‐1‐ethylpyrimidinium tetrafluoroborate is monoclinic a = 10.794, b = 13.361, c = 10.892 Å, β = 112.6°, space group P21/n, four molecules per unit cell.

6‐Ethoxy‐1,3‐diethyl‐1,4(3,4)‐dihydro‐4‐oxopyrimidinium tetrafluoroborate is monoclinic, a = 17.637, b = 14.054, c = 11.501 Å, β = 101.7°, space group C2/c, eight molecules per unit cell.

In both structures the fluoroborate ions are disordered. The bond distances in the π‐electron systems are reasonably well described in terms of a small number of resonance structures.
Immobilized NADH models: (Preliminary communication)
Authors: Pandit U.K. , Gase R.A. , Cabré F. R. Mas , den Breejen‐Metz V.
Published: September 2010

Reduction of trifluoroacetophenone by solid‐supported NADH models has been demonstrated and shown to be dependent upon the length of the spacer unit between the polymer surface and the reagent.
Studies on polypeptides XXII: A synthetic hexapeptide as a standard substrate for Chymosin (Rennin)
Authors: Schattenkerk Cecile
Published: September 2010

The preparation of the hexapeptide Leu‐Ser‐Phe‐Nle‐Ala‐Ile‐OMe, using “solution synthesis” is described. The hexapeptide is an excellent standard substrate for chymosin.
The chemistry of small‐ring compounds. Part 39. Displacements in cyclopropyl chlorides activated by electron‐donating substituents
Authors: van der Vecht J. R. , Steinberg H. , de Boer Th. J.
Published: September 2010

Cyclopropyl chlorides with a methoxy‐ or a p‐tolyl group linked to the same carbon atom as halogen undergo substitutions in polar solvents with relatively little ring rupture, when the nucleophile is sufficiently reactive (e.g. methanol, N−3, Br−) to trap the intermediate α‐substituted cyclopropyl cations.

Such substitution reactions are of the SN1 type and do not proceed via cyclopropene intermediates. With poor nucleophiles such as NO−3 in aqueous acetone, only polymeric ring‐opened products are formed.
Photolysis of some N‐cycloalkyl‐N‐halosulfonamides
Authors: Dekker E. E. J. , Engberts J. B. F. N. , de Boer Th. J.
Published: September 2010

N‐Cycloalkyl‐N‐halo‐tosylamides 1a‐c and 2a‐b with three‐, four‐ and five‐membered cycloalkyl groups have been photolysed in methanol/dichloromethane at −80° and −10°. The resultant ω‐halo‐alkylidenesulfonamides or N‐cycloalkylsulfonamides are formed as outlined in Schemes 1 and 2. The influence of ring size on the tendency towards ring fission in intermediate amidyl radicals ‐ resulting from N‐Cl (N‐Br) homolysis ‐ is closely analogous to such tendencies found in corresponding N‐nitroso derivatives: dominant ring rupture in cyclopropyl and cyclobutyl derivatives, and no ring fission in cyclopentyl derivatives.

Whatever the ring size, elimination of HCl or HBr with formation of a CN double bond does not take place in the photolysis of N‐halosulfonamides. This is in sharp contrast with the A'‐nitroso derivatives where exocyclic CN bond formation by HNO elimination of HNO is a common process for derivatives with a cyclobutyl or larger ring substituent.
Chemistry of peroxyacyl nitrates I. Thermal decomposition in cyclohexane solution; effect of added nitric oxide and of nitrogen dioxide
Authors: van Swieten A. P. , Louw R. , Arnoldy P.
Published: September 2010

The peroxyacyl nitrates 1b and 1c, in cyclohexane solution (0.01 − 0.1 M, 25‐60°C) decompose smoothly, displaying first‐order kinetics. Added nitrogen dioxide lowers the rate (approx. 3 x) but added nitric oxide results in a (7‐fold) rate enhancement, independent of the NO concentration. Under the latter circumstances the Arrhenius parameters for 1b are: log A/s−1 = 15.3, Ea = 26.7 kcal.mole−1.

Products from 1b include CO2 (>85%), RNO2, RONO, ROH and corresponding derivatives from solvent cyclohexane. 1b does not produce caproic acid, but m‐chlorobenzoic acid together with chlorobenzene (RH), are prominent products from the thermolysis of 1c.

These features are interpreted via a homolytic mechanism involving primary steps [1] and [2]. With added NO, step [1] is rate‐determining, whereas with added NO2 decomposition occurs via reaction [2].

The relevance of radical pair (cage) processes is outlined.

Attack on solvent occurs by transient free‐radical intermediates (e.g. R*, RO*) and by nitrogen dioxide.

The effect of other additives (such as dihydroanthracene, resulting in RCO3H as isolable product) is in accord with this mechanism.

Thermochemical‐kinetic features are discussed.
Metallation of 1,3‐dienyl ethers and 1,3‐dienyl sulfides in the 1‐position
Authors: Everhardus R. H. , Gräfing R. , Brandsma L.
Published: September 2010

1,3‐Dienyl ethers and the corresponding sulfides (CH2CHCHCHXR; XO, S; Ralkyl, phenyl) are readily metallated at C‐1, usingn‐butyllithium and KO‐t‐Bu in tetrahydrofuran. 2H‐Thiopyran can be lithiated at the 6‐position withn‐butyllithium and tetramethylethylenediamine in tetrahydrofuran. The various metallated compounds react smoothly with methyl iodide, methyl thiocyanate and acetaldehyde to give the expected derivatives. At about −20° a more than 95 % transformation of the metallated compound fromcisCH2CHCHCHStBu into thetrans‐isomer occurs; with smaller R groups (isopropyl or ethyl) a less complete inversion is observed.
Interaction energy calculations in zeolites. Part I. The electrostatic field in Y and A zeolites
Authors: Michelena Joseba A. , Vansant Etienne F. , de Bièvre Paul
Published: September 2010

To evaluate the interaction energy of molecules adsorbed in the Y and A zeolites, the electrostatic field has been calculated in the large cavities. The zeolites have been considered as crystals consisting of point charges, with the positive charges statistically localized at all cationic sites and the negative charges distributed equally among the lattice oxygens. In general, for both zeolites the electrostatic fields are mainly determined by the exchangeable cations. Furthermore, the calculations have shown that, in contrast with the Y zeolite, the field obtained in a large cavity of the A zeolite differs considerably when it is calculated with or without taking into account the ions belonging to the surrounding large cavities.
Interaction energy calculations in zeolites. Part II. The interaction energy of Ar, CO and CO2 molecules adsorbed in the zeolites NaY and CaY
Authors: Michelena Joseba A. , Vansant Etienne F. , de Bièvre Paul
Published: September 2010

The interaction energies of Ar, CO and CO2 molecules adsorbed in the large cavities of the zeolites NaY and CaY have been determined from the calculation of the dispersion, polarization, field‐dipole, field gradient‐quadrupole and repulsion components for different positions of the molecules. We have illustrated theoretically the non‐cation specificity of adsorbed Ar molecules and the cation‐specific behaviour of the CO molecules in Y‐type zeolites. A comparison between calculated interaction energies and the experimental isosteric heats has been carried out. A possible mechanism for the CO2 chemisorption has been suggested.
Cannabis XVIII: Isolation and synthesis of olivetol derivatives formed in the pyrolysis of cannabidiol
Authors: Luteyn J. M. , Spronck H. J. W. , Salemink C. A.
Published: September 2010

Pyrolysis of cannabidiol results in the formation of several new cannabinoids and cracking products. In an earlier paper several structures were proposed for the cracking products based on GCMS measurements. In this paper the isolation and synthesis of the majority of these cracking products ‐ which are in general C(2)‐substituted olivetol derivatives ‐ is described. 2,6‐Dimethoxy‐4‐pentylphenyl‐lithium and the cuprates derived therefrom proved to be very promising intermediates for the synthesis of olivetol derivatives specifically substituted at C(2). The versatility of these reagents is illustrated by several examples.
Chemistry of the SO bond. Part 7. The crystal structure of 1,1,3‐trimethyltrimethylene sulfite: A sulfite with an equatorial SO
Authors: Petit G. , Lenstra A. T. H. , van De Mieroop W. , Geise H. J. , Hellier Desmond G.
Published: September 2010

1,1,3‐Trimethyltrimethylene sulfite crystallizes in the monoclinic space group P21/c with a = 7.419 Å, b = 8.640 Å, c = 12.708 Å, β = 95.58° and Z = 4 at −90°C. The structure was solved using Patterson and difference Fourier techniques and refined by block‐diagonal least‐squares to a final R value of 6.9%.

The double bonded oxygen is found in the unusual equatorial position. The conformation features are compared with similar compounds having the S=O group in the common axial position.
Aromatic lead(IV) compounds IX: 13C‐FT‐NMR spectroscopy of compounds of the type Ar4Pb
Authors: de Vos D. , Wolters J.
Published: September 2010

13C chemical shifts and 207Pb‐13C coupling constants are reported for tetraaryllead compounds. These data demonstrate a strong dependence upon the nature and position of the substituent in the aromatic nucleus.