bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemistry of α‐nitrosulfones. Part I: Sulfinate elimination from α‐sulfonylnitroalkane anion radicals
Authors: Zeilstra J. J. , Engberts Jan B. F. N.
Published: September 2010

Electron transfer reactions to 2‐nitropropyl p‐tolyl sulfone (1) using different electron donors, are described. Using potassium 2‐propylnitronate as the electron donor, the product formation is proposed to occur via a free radical chain process involving rapid elimination of p‐toluenesulfinate anion from the anion radical derived from 1. When the carbon atom connecting the nitro and sulfonyl groups bears hydrogen, the corresponding α‐sulfonyl nitronate is formed as the only product under comparable conditions. Treatment of l‐iodo‐l‐nitro‐l‐(p‐tolylsulfonyl) propane with potassium 2‐propylnitronate in ethanol affords the potassium salt of l‐nitro‐l‐(p‐tolylsulfonyl) propane, 2,3‐dimethyl‐2,3‐dinitrobutane and iodine. Possible mechanisms for the formation of these products are briefly discussed.
On the occurrence of the SN(ANRORC)‐mechanism in the reaction of 2‐bromo‐4‐phenylpyrimidine with potassium amide in liquid ammonia
Authors: Kroon A. P. , van der Plas H. C.
Published: September 2010

On amination of 2‐bromo‐4‐phenylpyrimidine with potassium amide, 2‐amino‐4‐phenylpyrimidine, β‐amino‐β‐phenylacrylonitrile and 4‐amino‐l‐cyano‐2‐phenyl‐l‐aza‐1,3‐butadiene are formed.

2‐Bromo‐4‐phenyl‐[l,3‐15N]‐pyrimidine has been prepared and found to give on amination 2‐amino‐4‐phenylpyrimidine. which contains the original15N mainly in theexocyclicamino group. This is explained by a mechanism, involving an initial Addition of the Nucleophile to position 6, a subsequent Ring‐Opening by fission of the N(1)‐C(6) bond and Ring‐Closure (SN(ANRORC)‐mechanism).
Consecutive reactions in the thermal high pressure hydrogenolysis of tetralin and indan: Part II
Authors: Penninger J. M. L. , Slotboom H. W.
Published: September 2010

Reaction models were derived by analogue simulation, to describe the course of the reaction in the hydrogenolysis of tetralin and indan up to high conversion levels.

The side chain cracking of n‐butylbenzene results mainly in styrene, ethyl‐benzene and toluene; n‐propylbenzene preferentially forms styrene and ethyl‐benzene, while l‐methylindan undergoes demethylation and α ring‐opening almost exclusively at the methyl substituted C‐atom.

Mechanisms proceeding via benzylic radicals, are proposed for the side chain cracking.
Configuration of acetaldehyde azine; 1‐methyl‐2,3‐diazapentadienyl anions
Authors: Kloosterziel H.
Published: September 2010

1H NMR data of two anions formed in succession from the title compound prove the EE configuration.
The ESCA‐method as an additional tool for structure elucidation: Investigations of compounds derived from active methylene compounds and carbon disulfide
Authors: Kolind‐Andersen H. , Dalgaard L. , Jensen L. , Lawesson S.‐O.
Published: September 2010

The structures of various compounds derived from active methylene compounds and carbon disulfide have been determined by ESCA‐measurements of the binding energy of the 2p1/2 and 2p3/2 electrons of the two sulfur atoms in the compounds. The choices between alternative structures agree with statements from other methods of molecular spectroscopy (IR, NMR).
The tris(biuretato)cobaltate(III) ion: The crystal structure of potassium tris(biuretato)cobaltate(III) hydrate
Authors: Birker P. J. M. W. L. , Smits J. M. M. , Bour J. J. , Beurskens P. T.
Published: September 2010

The structure of the octahedral N6‐coordinated potassium tris(biuretato)‐cobaltate(III) hydrate, K3Co(HNCONHCONH)3. xH2O (x = 6.38) was determined by X‐ray analysis. The crystals are triclinic, space group \documentclass{article}\pagestyle{empty}\begin{document}$ \bar 1 $\end{document}, with unit cell dimensions a = 9.296, b = 11.168, c = 11.631 Å, α = 93.76°, β = 112.71°, γ = 74.57° and two formula units per cell. 3275 non‐zero reflections were measured with an automatic diffractometer. The structure was refined by full matrix least‐squares methods to a conventional R‐value of 0.05. The cobalt is in nearly regular octahedral coordination with an average Co‐N distance of 1.916 Å. The slightly puckered biuretato ligands are somewhat bent out of the plane formed by four coordinating nitrogen atoms and the cobalt atom.
Hydride transfer reactions: V. Kinetics and mechanism of the reduction of hydroxyallyl and tetrahydrofuryl ions with isobutane in HF‐SbF5 and HF‐BF3
Authors: Brouwer D. M. , Kiffen A. A.
Published: September 2010

Protonated mesityl oxide (1) and 3‐penten‐2‐one (3), and the 2,5,5‐trimethyltetrahydrofuryl (5) and 2,5‐dimethyltetrahydrofuryl (7) ions react with isobutane to give the corresponding saturated ketones and tert‐butyl ion. The reactions are very much faster in 9:1 HF‐SbF5 than in HF‐BF3; ions 1 and 5 react far more rapidly than 3 and 7, respectively. These “ionic hydrogenations” are concluded to take place via transfer of hydride ion from isobutane to the alkylcarbonium carbon of intermediate dications (C,O‐diprotonated alkenones). This mechanism also accounts for the findings that 5 and 7 are hydrogenated much more rapidly than 1 and 3, respectively, in spite of the fact that the former ions are thermo‐dynamically far more stable than the latter. The reversibility of these reactions has been demonstrated in the case of cation 5.
Studies on vitamin D and related compounds XXIII: The structure of bischolestadienol isomers
Authors: Boomsma F. , Jacobs H. J. C. , Havinga E. , van der Gen A.
Published: September 2010

The photodimerization product of 7‐dehydrocholesterol was found to consist of three isomers to which structures 4b, 5b and 6b are assigned.
Chemistry of α‐nitrosulfones. Part III. A new convenient synthesis of α‐nitrosulfones
Authors: Zeilstra J.J. , Engberts Jan B. F. N.
Published: September 2010

A number of x‐nitrosulfones have been prepared in reasonable yields by reaction of p‐toluenesulfonyl iodide with metal nitronates. The reaction is a free radical chain process rather than a nucleophilic displacement of iodide by the nitranion. A possible reaction path involving the intermediacy of x‐iodonitroalkane radical anions is indicated. The synthetic procedure could be simplified by adding iodine to a solution of sodium p‐toluenesulfinate and the appropriate potassium nitronate in DMF. The mass spectra of several x‐nitrosulfones are briefly discussed.
Chemistry of acetylenic ethers 104 Thermal rearrangement of 1‐alkynyl 2‐alkynyl sulfides in the presence of dialkylamines or dialkylphosphines. A new type of thio‐claisen rearrangement
Authors: Meijer J. , Vermeer P. , Bos H.J.T. , Brandsma L.
Published: September 2010

1‐Alkynyl 2‐alkynyl sulfides, R1CCS‐CH2CCR2, 1, rearrange at room temperature (if R2 = H) or upon heating (if R2 = alkyl). The thioketenes, H2CCC(R2)‐C(R1)CS, 2, presumed to be formed can be trapped by secondary amines, or‐in some cases‐by dialkylphosphines. Depending upon the nature of the substituents R1 and R2 and upon the solvent, allenic thioamides, H2CCC(R2)‐CH(R1)C(S)NR32, 3, conjugated dienic thioamides, H2CCHC(R2)C(R1)C(S)NR32, 4, thiophene derivatives, 5, or mixtures of these types of compounds, are formed.
Intramolecular catalysis in cis‐diethyl 2‐carboxyvinylphosphonate hydrolysis
Authors: van der Holst J. P. J. , van Hooidonk C. , Kienhuis H.
Published: September 2010

The hydrolysis of the title compound proceeds very fast in weakly acidic aqueous media by a stepwise release of both ethyl ester groups via phosphorus‐oxygen bond fission. The reactions are about 106 times faster than that for the release of one ethyl group of the corresponding trans‐isomer. The observed kinetics are consistent with a mechanism involving intramolecular catalysis by the undissociated carboxyl group.
A regiospecific N‐substitution of asymmetrically alkylated imidazoles: The preparation of 1,5‐dialkyl‐ and 1,2,5‐trialkylimidazoles
Authors: Godefroi E. F. , Mentjens J. H. F. M.
Published: September 2010

Abstract. A method for regiospecific N‐alkylation of 4 (or 5)‐methylimidazoles (1a‐c) to 1,5‐disubstituted and 1,2,5‐trisubstituted derivatives has been elaborated. The process consists of the regiospecific N‐acetylation of 1a‐c to give isomerically pure 3a‐c; these are quaternized and deacetylated to 5a‐j. When simplified to a one‐pot synthesis, yields up to 40% of N‐substituted products are realized.
Electron transfer reactions between trivalent phosphorus compounds and activated ketones
Authors: Boekestein G. , Voncken W. G. , Jansen E. H. J. M. , Buck H. M.
Published: September 2010

The present paper presents a mechanism for the reaction between trivalent phosphorus compounds ‐ P(OR)3, R = alkyl and P {N(CH3)2}3 ‐ and molecules with activated carbonyl groups such as α‐diketones, o‐quinones and α,β‐unsaturated ketones. It appeared from ESR measurements that intermediate radicals which originate in a high concentration are converted into oxyphosphoranes. In the case of P(OR)3 an intramolecular shift could be established as a side reaction. Furthermore a number of interesting spin adducts are formed between phosphinium radicals and the scavenger 2‐methyl‐2‐nitrosopropane.
Synthesis of 1‐alkenyl derivatives of isothiocyanates, dithiocarbamates and thioureas
Authors: Hoff S. , Blok A. P.
Published: September 2010

Reductive cleavage of the sp3 carbon‐sulfur bond in alkyl‐or aryl‐substituted 2‐mercapto‐or 2‐amino‐6H‐1,3‐thiazines with sodium in liquid ammonia affords almost quantitative yields of the sodium salts of 1‐alkenyl‐dithiocarbamates and ‐thioureas, respectively. The dithiocarbamates can be converted into 1‐alkenyl isothiocyanates by reaction with chloroformates and subsequent pyrolysis to give overall yields of 54‐88%. Cis‐trans isomerization of the 1‐alkenyl isothiocyanates can only be achieved by irradiation.
Preparation and ESR of phosphorus spiro compounds. Part III
Authors: Rothuis R. , Freide J. J. H. M. Font , van Dijk J. M. F. , Buck H. M.
Published: September 2010

The synthesis of 2,2′‐biphenylenediphenylphosphonium, 2,2′‐biphenylenephenylbenzylphosphonium and 2,2′‐biphenylenephenyl(p‐nitrophenyl)phosphonium salts is described. The related phosphoranyl radicals I, IV and V, generated by electrochemical reduction, are measured by ESR spectroscopy. A similar procedure is followed for the radicals II and III; related phosphonium compounds are described in the literature.

The small values of the phosphorus doublet splitting constants are an indication for a tetrahedron (T) like configuration of the phosphorus. The odd electron is delocalized in the aromatic ligands and the five 3‐dorbitals of the phosphorus.

It is shown that the spin‐ and odd electron density distribution depends on the electron affinity of the aryl ligands. This is confirmed by quantum chemical calculations.
Conformational analysis of cis‐ and trans‐1,2‐di‐tert‐butylcyclohexane and some homomorphs
Authors: van de Graaf B. , van Bekkum H. , van Koningsveld H. , Sinnema A. , van Veen A. , Wepster B. M. , van Wijk A. M.
Published: September 2010

Spectroscopic data of cis‐ and trans‐1,2‐di‐tert‐butylcyclohexane (cis‐ and trans‐1) and of some of their homomorphs are discussed with respect to the conformations of these compounds. For the cis compounds a chair conformation, in which the rotation of at least one of the substituents is hindered, explains the experimental data (PMR, CMR and IR).

IR spectra indicate that in solution the trans compounds exist to a large extent in a non‐chair conformation. Analysis of a Eu(dpm)3 shifted PMR spectrum of trans‐1,2‐bis[2‐(methoxycarbonyl)‐2‐propyl]‐cyclohexane (trans‐2) and of CMR data for trans‐1 shows that certainly a chair conformation with equatorial substituents is not favoured. As it has been shown that trans‐2 has a chair conformation with axial substituents in the crystal, it is concluded that in solution the trans compounds examined probably exist as a conformational mixture, a twist conformation and a chair conformation with axial substituents being the major components.

A rationale for these conclusions is offered on the basis of the several severe interactions present in the various conformations.
Synthesis of 2,1‐benzisoxazoles (analogues of psilocine and muscimol)
Authors: du Crocq H. , Lousberg R. J. J. Ch. , Salemink C. A.
Published: September 2010

The synthesis of several 2,1‐benzisoxazoles with substituents at different positions of the six‐membered ring and with a variable aliphatic side‐chain at C‐3 is reported. Anomalous reactions and complications, encountered in this synthesis, are dealt with.
The reactions of 6‐chloro‐ and 6‐bromo‐2,3‐dimethylquinoxaline with potassium amide in liquid ammonia
Authors: Czuba W. , Poradowska H.
Published: September 2010

Amination of 6‐halogeno‐2,3‐dimethylquinoxalines resulted in the formation of 5‐amino‐and 6‐amino derivatives. The reaction was found to involve intermediate formation of 5,6‐didehydro‐2,3‐dimethylquinoxaline.
Reactions of 1‐ and 3‐bromoisoquinoline with potassium amide in liquid ammonia. Nucleophilic substitution of 3‐bromoisoquinoline by the ANRORC mechanism
Authors: Sanders Georgine M. , van Dijk M. , den Hertog H. J.
Published: September 2010

Both 1‐ and 3‐bromoisoquinoline are converted by potassium amide in liquid ammonia into the corresponding amino derivatives in excellent yields. It is shown that the amination of 3‐bromoisoquinoline proceeds as for 55% by the SN(ANRORC) mechanism via an open‐chain compound, while the remaining 45% substitution, as well as the substitution in 1‐bromoisoquinoline, occurs probably by the AE mechanism.

When heated with ethanolic ammonia at 130°C 3‐bromoisoquinoline is transformed into 3‐aminoisoquinoline to the extent of 27% by the SN(ANRORC) mechanism; thus this mechanism may well occur with other reagents also.
Caractérisation des ions VOCl3Br2− et [VOCl3(CH3CN)]−
Authors: Brunette J. P. , Leroy M. J. F.
Published: September 2010

[(C2H5)4N]2VOCl3 Br and (C2H5)4N[VOCl3(CH3CN)] have been synthesized by reaction of VOCl3 with (C2H5)4 NBr and (C2H5)4NI. Conductivity measurements and visible spectra have been obtained from solutions of the compounds in CH3CN. VOCl3Br2− and [VOCl3(CH3CN)]− anions have been characterized in the solid state by infrared spectroscopy: the complex ions are monomeric, with the vanadium most probably five‐coordinated.
On some problems of the hydrogenation of benzene on nickel and nickel‐copper alloys
Authors: van Barneveld W. A. A. , Ponec V.
Published: September 2010

A comparison is made of the activity of the Ni catalyst and alloys with 5 and 10 at % Cu, in the hydrogenation of benzene. While at low temperatures (< 100°C) Ni is more active, at higher temperatures the situation is reversed; the reason is the presence of side‐reactions as hydrogenolysis and coke formation. Alloying of Ni with Cu has a much more pronounced effect on the reactions of CC bonds (side reactions) than of CH bonds.
Recherche d'effets stériques dans la réactivité de la norbornanone‐2 par la mesure des effets isotopiques secondaires du deuterium
Authors: Boyer B. , Lamaty G. , Roque J. P. , Geneste P.
Published: September 2010

The following compounds have been prepared: 2‐norbornanone‐3d1 exo, ‐3‐d1 endo, ‐ 3,3‐d2 and 5,6‐d2 endo; the rates of borohydride ion addition and of decomposition of bisulfite addition compounds have been measured in order to explain the high exo side reactivity of norbormyl systems. In both reactions, there is no significant isotope effect due to deuteration at the 5,6 endo positions. This observation can result either from an absence of any steric interaction or from a non‐bonded interaction potential much smaller than usually admitted. The protons in 3‐endo and 3‐exo positions are not equivalent towards the nucleophile approach.
Peroxidation and bromination of thujopsene
Authors: Traas P. C. , van der Linde L. M. , Takken H. J.
Published: September 2010

We have confirmed that treatment of thujopsene (1) with peracetic acid and m‐chloro‐perbenzoic acid occurs exclusively from the side (β) towards the cyclopropane ring in the molecule, while osmium tetroxide reacts from the α‐ as well as from the β‐side. It was found that reaction of the unisolated intermediate epoxide 2 with acetic acid and m‐chlorobenzoic acid yields, besides the thujopsanones (4) and (5), 2β‐hydroxy‐3β‐acetoxythujopsane (7) and 2β‐(m‐chloro‐benzoyloxy)‐3β‐hydroxy thujopsane (3), respectively, and not 2α‐acetoxy‐3β‐hydroxythujopsane (11) and 2α‐(m‐chlorobenzoyloxy)‐3β‐hydroxythujopsane (10) in contrast with what was previously reported by other authors. Reaction of thujopsene with hypobromous acid and bromine yields, in both cases, 3‐bromothujopsene (21).
Ring transformations in reactions of heterocyclic halogeno compounds with nucleophiles (XXXVII). A 15N study on amination and isoxazole formation in reactions of 6‐substituted 4‐chloro‐ and 4‐phenoxypyrimidine 1‐oxides with liquid ammonia and with potassium amide in liquid ammonia
Authors: Peereboom R. , van der Plas H. C.
Published: September 2010

Treatment of 4‐chloro‐6‐R‐[1(3)‐15N]pyrimidine 1‐oxide (RCH3, C6H5) with liquid ammonia at − 33°C yields 4‐amino‐6‐R‐pyrimidine 1‐oxide (RCH3, C6H5), which contains no 15N‐label in the amino group. The amino‐dechlorination does not take place according to an SN(ANRORC) mechanism. The same results were obtained with solutions of potassium amide in liquid ammonia at − 75°C. Furthermore, 4‐chloro‐5‐deutero‐6‐phenylpyrimidine 1‐oxide in liquid ammonia yields a 4‐amino‐5‐deutero‐6‐phenylpyrimidine 1‐oxide with the same D content as the starting material, thus excluding an SN(EA) process. It was found that the reaction of 4‐chloro‐6‐methyl‐[1(3)‐15N]pyrimidine 1‐oxide with liquid ammonia at − 33°C and with potassium amide in liquid ammonia at − 75°C, to 5‐amino‐3‐methylisoxazole is accompanied by loss of 15N. The 15N label was unequally distributed over the nitrogen of the ring and the amino group. Two concurrent mechanisms: one, involving the addition of the amide ion to C(2), the other to C(4) of the pyrimidine ring are proposed. Since the 5‐amino‐3‐methylisoxazole obtained from reaction of 6‐methyl‐4‐phenoxy‐[1(3)‐15N]pyrimidine 1‐oxide with potassium amide in liquid ammonia at − 33°C shows no lowering of the 15N content, only an initial addition of the amide ion to C(2) ‐ and not to C(4) takes place in this ring contraction.
Ring transformations in reactions of heterocyclic compounds with nucleophiles (X). A novel pyrimidine rearrangement reaction
Authors: van der Plas H. C. , Vollering M. C.
Published: September 2010

The ring interconversion of 5‐(1‐hydrazonoethyl)‐2,4‐dimethylpyrimidine into 4‐acetyl‐3‐methylpyrazole azine and of 5‐[1‐(hydroxyimino)ethyl]‐2,4‐dimethylpyrimidine into 5[1‐(hydroxyimino)ethyl]‐3‐methylisoxazole is described. These new ring transformations take place by an attack of the nucleophilic end of the side‐chain at position 5 of the pyrimidine ring to C(6) with simultaneous fission of the N(1)‐C(6) bond.
Chemistry of acetylenic ethers 108 Stereospecific addition of organocopper(I) reagents to 1‐alkynyl sulfones
Authors: Meijer J. , Vermeer P.
Published: September 2010

1‐Alkynyl sulfones R1CCSO2‐R2, 1 are very prone to addition of organo‐copper(I) reagents “RCu”. The stereochemistry in the vinylic sulfones RR1CCHSO2‐R2, 2 so produced appeared to be dependent on the relative amounts of copper(I) bromide and the Grignard RMgX (X = Cl, Br) from which the organocopper(I) compound “RCu” was prepared. When an excess of copper(I) bromide was used the addition proved to be almost exclusively a cis‐addition in most cases.
Photoaddition of phenanthraquinone to alkyl‐substituted (alkylthio)acetylenes. Chemistry of acetylenic ethers 109
Authors: Mosterd A. , Lecluijze R.E.L.J. , Bos H.J.T.
Published: September 2010

Photoaddition of phenanthraquinone (1) to alkyl‐substituted (alkylthio)acetylenes (2: R2‐C≡CSR1) affords unsaturated (alkylthio)‐1,4‐diketones (5) formed by [2 + 2]‐cyclo‐addition. By irradiation and by chromatography on alumina these 1,4‐diketones (5) are converted into 2‐hydroxyfuranones (6). Treatment of 5 with tin(II) chloride in acetic acid affords 3‐(alkylthio)phenanthro[9,10‐b]furans (7).
Photochemical cyclo‐addition of 9,10‐phenanthraquinone to phenylallene. Kinetics and temperature effects
Authors: Koster R.J.C. , Bos H.J.T.
Published: September 2010

Rate constants at various temperatures for the photocyclo‐addition reaction of 9,10‐phenanthraquinone (PQ) with phenylallene (2), were determined in benzene. ΔH≠ = 4.2 kJ.Mol−1 and ΔS≠ = −72 J.Mol−1.K−1 were calculated.

Detailed product analysis revealed besides the known type of [4 + 2]‐cyclo‐adducts (dihydrodioxins, 3 and 4), a [2 + 2]‐cyclo‐adduct (oxetane, 5) and a hydrogen abstraction product (6).
Aromatic lead(IV) compounds VI. PMR spectroscopy of para‐substituted aryllead compounds
Authors: de Vos D. , van Der Kooi H.O. , Wolters J. , van Der Gen A.
Published: September 2010

PMR data on several series of para‐substituted aryllead compounds are presented. An attempt is made to explain the variation in lead‐proton coupling constants in terms of changes in hybridization and charge on the lead atom.
Photodehydrocyclizations of stilbene‐like compounds XIV Photosynthesis and photoreactions of 1,2‐ and 1,14‐diphenylpentahelicene derivatives
Authors: Laarhoven W.H. , Boumans P.G.F.
Published: September 2010

Two polycyclic aromatics having a phenyl‐substituted pentahelicene moiety, 13,14‐diphenyldibenzo[c,g]chrysene (19) and 14,15‐diphenyldibenzo[f,j]picene (38) have been obtained by irradiation of the appropriate diarylethylenes (13 and 18). Further irradiation of 19 in benzene yields mainly dibenzo[a,g]coronene (21) by cyclodehydrogenation with simultaneous loss of a phenyl substituent. The side products of this reaction are probably formed via rearrangements similar to those previously found during the photoreaction which occurs on irradiation of 1,12‐diphenyltriphenylene. Their most probable structures are 15‐phenyldibenzo[a,g]coronene (28) and 15‐phenyldibenzo[a,ghi]naphtho[2,1,8a,8‐cde]perylene (31). Irradiation of 19 in ethyl acetate yields only 28 (main product) and 31. Photocyclization of 38 could not be effected. NMR data for the cis‐trans isomers of the starting compounds (13 and 18) revealed that the cis isomers exist mainly in the overcrowded syn conformation.
A proton magnetic resonance study of the influence of the solvent on the rotation about the carbamate amide bond in N‐(benzyloxycarbonyl)‐L‐proline t‐butyl ester
Authors: de Leer E.W.B. , van der Toorn J.M.
Published: September 2010

The NMR spectrum of N‐(benzyloxycarbonyl)‐L‐proline t‐butyl ester shows two t‐butyl signals of slowly interconverting syn and anti rotamers. The t‐butyl signals have been assigned to the syn and the anti form by using Eu(fod), as a shift reagent. The thermodynamic parameters ΔG≠, ΔH≠ and ΔS≠ for rotation about the amide bond have been determined by the method of Shanan — Atidi and Bar‐Eli and by complete line shape analysis, in four solvents of different polarity. The results are discussed.
4‐Methylprotoadamant‐4‐en‐2‐one: An unexpected product from the reaction of l‐methyladamantan‐2‐one with sodium azide and methanesulfonic acid
Authors: Peters J.A. , van Der Toorn J.M. , van Bekkum H.
Published: September 2010

4‐Methylprotoadamant‐4‐en‐2‐one was isolated from the reaction of 1‐methyladamantan‐2‐one with sodium azide and methanesulfonic acid. A side product of this reaction is probably 4‐methyleneprotoadamantan‐2‐one.
Proton chemical shifts and charge densities
Authors: Kloosterziel H. , Werner M.A.
Published: September 2010

From the P.M.R. spectra of phenylcyclopentadienide anion and of phenyltropylium cation it is concluded that the proportionality factor between the proton chemical shift and the charge density of 10 ppm per unit charge is not well founded.
Electrochemical reduction of aza‐aromatics. Part V Influence of fluorine substitution on the electron affinities
Authors: van den Ham D. M. W. , Harrison G. F. S. , Spaans A. , van der Meer D.
Published: September 2010

The electrochemical reduction process of fluoro‐substituted aza‐aromatics can well be described by the pattern which is normally postulated for aryl halogenides, i.e. fission of the carbon‐halogen bond. However, the stability of the intermediate mono‐negative ions is generally higher than for the comparable fluoro‐substituted arenes. As an example of this stability, the ESR spectrum of tetrafluoroquinoxaline is given. The half‐wave reduction potentials of the first reduction wave can be related to the electron affinities of the molecules. These electron affinities have been correlated with those obtained by semi‐empirical quantum‐chemical calculations.
Vapour pressure and structure of selenium trioxide
Authors: Bleijerveld R. H. T. , Mijlhoff F. C.
Published: September 2010

The uncertainty about the constitution of the vapour of selenium trioxide has been settled. It is concluded that only tetramer molecules are present. A new value for the heat of sublimation has been found: 17.7 ± 0.8 Kcal/mole Se4O12, as well as for the heat of evaporation: 15.4 ± 0.2 Kcal/mole Se4O12.
Addition of phenols and alcohols to ethoxyethyne Formation of orthoacetates or ketene acetals
Authors: Broekema R.J.
Published: September 2010

Addition of phenols and of alcohols to ethoxyethyne, under the influence of mercury(II) acetate and zinc chloride respectively, affords orthoacetates. Ketene acetals can be isolated with sterically hindered phenols.
Stereoselectivity and proton binding in copper(II) complexes of aspartic acid, glutamic acid and some N‐methyl or N‐benzylhistidine derivatives
Authors: Ritsma J.H.
Published: September 2010

Stability constants and stereoselective effects are measured for copper(II) complexes with aspartate (asp), glutamate (glut), histidinate (his) and some N‐alkylhistidinate derivatives: N‐methyl‐ (mhis), N,N‐dimethyl‐ (dimhis) and N‐benzylhistidinate (bhis). For the dicarboxylic amino acids the predominant species in solution are CuA, CuHA and CuA2 *; for histidine and its derivatives:CuA, CuHA, CuA2 and CuHA2. By comparison of competition constants (vide infra) it is found that the ligand is bound via its glycine‐locus in all complexes CuHA. For complexes CuHA2, the mono‐protonated ligand, HA, is also bound to copper by its glycine‐locus if A = his and bhis, and mainly so if A = mhis, but, if A = dimhis, HA, possibly, is monodentate and bound to copper by its imidazole group. No stereoselective effects are found in complexes CuA2 for A = asp, glut, his and mhis; for A = dimhis a significant positive effect (i.e. in favour of the meso complex Cu(DA)(LA)) is found, in contrast to the case for A = bhis. In the protonated copper complexes CuHA2, small negative effects are found for A = his, mhis and bhis, but no effect for dimhis.
Détermination de configurations de dérivés styréniques et stilbéniques di‐ et tri‐substitués par résonance magnétique nucléaire
Authors: Doré Jean‐Christophe , Viel Claude
Published: September 2010

The rules of Pascual, which allow one to determine by calculation, a priori, the configuration E or Z of an ethylenic compound, enabled the authors to verify, to reassign or to assign the exact configuration of numerous derivatives of styrene or stilbene carrying different substituents on their double bond carbon atoms.

Certain anomalies observed in the case of α,β‐ethylenic ketones in the experimental values and those calculated by the Pascual increments, enabled the authors to attribute these divergencies to the S‐cis or S‐trans conformations and to estimate their relative importance.
The effect of pressure on the base‐catalysed isomerizations of gem‐dimethyl‐ and isopropyl‐cyclohexenes. Part 6
Authors: van Hoboken N. J. , Wiering P. G. , Steinberg H.
Published: September 2010

The isomerization of gem‐dimethylcyclohexenes and of isopropylcyclohexenes in a solution of potassium tert‐butoxide in dimethyl sulfoxide have been studied as a function of temperature (70°‐98°C) and pressures up to 3000 atm. The activation volumes for the proton abstraction reactions are found to be negative (‐18 to‐25 cm3/mole) and are attributed to an electrostriction of the solvated, negatively charged transition state and partly to the negative activation volume for ionization of potassium tert‐butoxide.
Generation of nitroxides with a chloro or nitro substituent in β‐position
Authors: Kayen A. H. M. , Bolsman Th. A. B. M. , de Boer Th. J.
Published: September 2010

Nitroxides 1 with a chloro or nitro substituent in the ß‐position can be generated by three methods: addition of radicals to gem‐chloro nitroso‐ or gem‐nitro nitroso compounds (reaction 1), addition of chloro‐ or nitroalkyl radicals to nitroso compounds (reaction 2), and addition of atomic chlorine to nitrones (reaction 3). With nitrogen dioxide instead of chlorine, ß‐nitronitroxides cannot be obtained, because NO2 adds to nitrones via oxygen in a presumably charge‐controlled process. The presence of the chloro or nitro substituent in the ß‐position influences the unpaired spin density at nitrogen and thus lowers the nitroxide splitting constant.

The ESR signals of the nitroxides 1 clearly show the hyperfine splittings caused by the ß‐substituent. In the presence of nitric oxide, ß‐chloronitroxides cannot be detected and ß‐nitronitroxides only with difficulty.
NMR studies on σ‐adducts of heterocyclic systems with nucleophiles (Part VIII)13C‐NMR data of pyridazines and some of their covalent amination products
Authors: Klinge D. E. , van der Plas H. C. , van Veldhuizen A.
Published: September 2010

13C‐NMR data of several 3‐mono‐ and 3,6‐di‐substituted pyridazines, 3‐, 4‐ and 6‐mono‐ and 3,6‐di‐substituted pyridazine 1‐oxides and 4‐nitro‐3,6‐disubstituted pyridazine 1‐oxides are reported. 13C substituent effects of some substituents in the 3‐, 4‐ and 6‐position of the pyridazine ring and that of the N‐oxide function are calculated. The 13C‐NMR spectra of the σ‐adducts of 4‐nitro‐3,6‐disubstituted pyridazine 1‐oxides with liquid ammonia are described.
A stereospecific synthesis of cis‐ and trans‐1‐alkenyl sulfides from 1‐alkynyl sulfides and a copper(I) hydride complex or lithium tetrahydridoaluminate
Authors: Vermeer P. , Meijer J. , Eylander C. , Brandsma L.
Published: September 2010

1‐Alkynyl sulfides R1C≡C‐S‐R2 1 are easily converted with a copper(I) hydride complex in tetrahydrofuran into cis‐1‐alkenyl sulfides R1CHCH‐S‐R2 2 in yields >90%. Treatment of compounds 1 with LiAlH4 in the same solvent leads to the isomeric trans‐1‐alkenyl sulfides R1CH CH‐S‐R2 3 in almost quantitative yield.
Reactions of bromoethoxyisoquinolines with potassium amide in liquid ammonia
Authors: Sanders Georgine M. , van Dijk M. , den Hertog H.J.
Published: September 2010

Of the six possible isoquinolines with both a bromo and an ethoxy substituent in the pyridine nucleus, all, except 4‐bromo‐3‐ethoxyisoquinoline, react by simple nucleophilic substitution of the bromo atom and, if placed in position 1, of the ethoxy group. 4‐Bromo‐3‐ethoxyisoquinoline yields a complicated reaction mixture, containing in addition to substitution products dehalogenated compounds and at least five different substituted biisoquinolines.
Cleavage of dimethyl sulfoxide by alkali metals
Authors: Brandsma L. , Meijer J. , Verkruijsse H. D.
Published: September 2010

Reaction of dimethyl sulfoxide with two equivalents of lithium in liquid ammonia gives a solution of lithium methanesulfenate which can be alkylated or benzylated to yield the corresponding sulfoxide.
Electron donor‐acceptor cyclophanes II. Synthesis and electron impact induced fragmentation of cyclophanes derived from 1,2:4,5‐benzene‐ or 1,8:4,5‐naphthalene‐tetracarboxylic diimides
Authors: Schroff L. G. , Zsom R. L. J. , van der Weerdt A. J. A. , Schrier P. I. , Geerts J. P. , Nibbering N. M. M. , Verhoeven J. W. , de Boer Th. J.
Published: September 2010

The condensation of amines of the general type H2N‐(CH2)n‐D‐(CH2)m‐NH2 (D is an aromatic system with electron donor properties) with 1,2:4,5‐benzene‐tetracarboxylic dianhydride or with 1,8:4,5‐naphthalene‐tetracarboxylic dianhydride under high dilution conditions is shown to lead to the formation of electron donor(D)‐acceptor(A) cyclophanes of the type magnified image containing the 1,2:4,5‐benzene‐tetracarboxylic diimide or the 1,8:4,5‐naphthalene‐tetracarboxylic diimide group as an electron acceptor.

The fragmentation pattern of the cyclophanes upon electron impact is studied and found to agree completely with the proposed structures.
The reactions between 3′‐methyl‐6‐nitrospiro(2H‐1‐benzopyran‐2,2‐benzothiazolines] and 1,1‐bis[4‐(dimethylamino)phenyl]ethylene and the reactions of salicylaldehydes with 1,1‐bis[4‐(dimethylamino)phenyl]propene. A striking effect of an extra methyl group; photochromic chromenes
Authors: Zwanenburg D. J. , Maas Th. A. M. M.
Published: September 2010

The reactions between 1,1‐bis[4‐(dimethylamino)phenyl]ethylene (Michler's ethylene, 4) and 3′‐methyl‐6‐nitrospiro[2H‐1‐benzopyran‐2,2′‐benzothiazoline] (5, which exists in the open merocyanine form3), and its 3‐methyl derivative 10, respectively, were studied. The methyl group in the 3‐position in 10 has a great influence on the reactivity of this spiropyran at the 4‐position; 5 reacts with 4 giving 2,2‐bis[4‐(dimethylamino)phenyl]‐4‐{2,2‐bis[4‐(dimethylamino)phenyl]vinyl}‐6‐nitrochroman (9), whereas no change of the starting products was observed in the reaction of 10 with 4.

The same striking effect of an extra methyl group was found in the reaction of salicylaldehydes with 1,1‐bis[4‐(dimethylamino)phenyl]propene (11). In these cases we isolated the 1:1 products, 2,2‐bis‐[4‐(dimethylamino)phenyl]‐3‐methyl‐2H‐chromenes (13) whereas reactions of salicylaldehydes with 1,1‐bis[4‐(dimethylamino)phenyl]ethylene give only 1:2 products.
Beckmann rearrangement of aldoximes catalyzed by transition metal salts: A dehydration‐hydration reaction
Authors: Leusink A. J. , Meerbeek T. G. , Noltes J. G.
Published: September 2010

The Beckmann rearrangement of aldoximes catalyzed by transition metal salts like palladium and nickel acetylacetonates is shown to be a dehydration‐hydration reaction in which the anti‐oxime is converted into nitrile and the nitrile is converted into amide.
Mechanism of the inhibition of autoxidation by thiophenes
Authors: van Tilborg W.J.M. , Smael P.
Published: September 2010

The antioxidant action of thiophenes is shown to be due to a heterolytic decomposition of hydroperoxides effected by SO2 (H2SO4) which is liberated from the thiophene. Thus, the initiation level in an autoxidizing alkylaromatic compound (n‐hexylbenzene) is decreased and the oxidation is further inhibited by phenol, the heterolysis product of the hydroperoxide. At low thiophene concentrations the inhibition is counterbalanced by the low initiation level in such a way that the oxidation continues to proceed at a constant rate. The effect of substituents, of the concentration and of added bases on the antioxidant activity of thiophenes is reported.
Esters β‐thiocétoniques cyclaniques N° 2 Action des organo‐magnésiens sur ces composés
Authors: Paquer D. , Smadja S.
Published: September 2010

Alicyclic β‐thioxo esters react with Grignard reagents to give S‐addition, C‐addition and reduction reactions.

When the starting material has a five‐membered ring rearrangement reactions take place.
Synthesis of racemic and of (+)‐ and (‐)‐1‐methyldihydrothebainone. (Chemistry of opium alkaloids, Part IV)
Authors: Beyerman H.C. , Buurman E. , Maat L. , Olieman C.
Published: September 2010

Racemic 1‐(5‐benzyloxy‐4‐methoxy‐2‐methylbenzyl)‐1,2,3,4‐tetrahydro‐6‐methoxyisoquinoline (rac. 3) was synthesized (Scheme 1). Resolution with (+)‐ and with (‐)‐6,6′‐dinitrobiphenyl‐2,2′‐dicarboxylic acid yielded (‐)‐ and (+)‐3, respectively. By a Birch reduction, followed by N‐formylation, and by acid‐catalysed cyclization, we obtained in high yield racemic, (‐)‐, and (+)‐N‐formyl‐1‐methylnordihydrothebainone (6), respectively. In two ways, by direct reduction and by deformylation followed by reductive methylation, 6 could be converted selectively into racemic, and (‐)‐, and (+)‐1‐methyldihydrothebainone (7).

Synthetic (‐)‐7 was found to be identical with (‐)‐1‐methyldihydrothebainone prepared from natural material. This completes the proof of the structure.

The optical rotatory dispersion spectra are discussed.
Preparation, structure and properties of dicopper tris(N,N‐dialkyldithiocarbamato)dihalogeno compounds, Cu2(R2dtc)3X2, with copper in the oxidation states II and III
Authors: van de Leemput P. J. H. A. M. , Cras J.A. , Willemse J. , Beurskens Paul T. , Menger E.
Published: September 2010

The preparation, some magnetic and spectral properties of the compounds Cu2(R2dtc)3X2* (R = Me and Et, X = Br; R = Me, X = Cl) and the crystal structure of Cu2(Et2dtc)3Br2 are reported.

The compound, crystallizing in the monoclinic space group Cc [α = 14.421(15), b = 12.980(17), c = 15.152(11) Å and β = 106.82(8)°], contains four formula units per unit cell. The structure, which was refined to a conventional R value of 0.06 for 724 independent non‐zero reflections, consists of chains of alternating Cu(Et2dtc)2 and Cu(Et2dtc)Br2 units, both with copper in a distorted octahedral coordination.

The copper atom in the former unit has Cu‐S distances of 2.16(2), 2.20(2), 2.19(2), 2.26(2) and 3.27(3) Å and a Cu‐Br distance of 2.97(2) Å; the copper atom in the latter unit has Cu‐S distances of 2.27(2), 2.29(2), 2.94(4) and 3.00(3) Å and Cu‐Br distances of 2.40(2) Å. These distances suggest the compound to be composed of [Cu(III)(Et2dtc)2]+ and [Cu(II)(Et2dtc)Br2]− ions. The two C‐N and Cu‐S stretching frequencies are in accord with the presence of both Cu(III) and Cu(II).
Addition and substitution reactions of arylthio, arylsulfinyl and arylsulfonyl substituted sulfines with thiols
Authors: Veenstra G.E. , Zwanenburg B.
Published: September 2010

Stepwise oxidation ofp‐tolylp‐methoxydithiobenzoate (1) gives the sulfines (thione oxides) AnC(=S=O)STol (2), AnC(=S=O)SOTol (3) and AnC(=S=O)SO2Tol (4) (An =p‐CH3OC6H4and Tol =p‐CH3C6H4). Reaction of2withp‐toluenethiol (TolSH) in the presence of Et3N furnishes AnCH(STol)SSTol (5). The sulfine4yields with TolSH/Et3N5and AnCH2SO2Tol (6), with EtSH/Et3N AnCH(SEt)SSEt (7) and witht‐BuSH/Et3N the sulfone6. The sulfine3gives with TolSH/Et3N 5 and witht‐BuSH/Et3N6. In the presence of ZnCl2all three sulfines give rise to deoxygenated products,viz. dithioesters like1and AnCSSEt (8). In the absence of a catalyst, sulfine2, with TolSH and EtSH, undergoes deoxygenation to dithioesters.

Sulfine4gave with EtSH the dithioester8as the principal product, whereas with TolSH besides1and5the compound AnCH(SO2Tol)SSTol (9) was obtained. From sulfine3products were obtained that point to a disproportionation into2and4prior to the reaction of thiol with the sulfine function. In the discussion, a rationale is presented for the reactions observed. It is shown that nucleophilic attack of thiol or thiolate anion may occur at the sulfine sulfur as well as the sulfine carbon atom. In the presence of Et3N both reaction modes take place, whereas in the presence of ZnCl2attack at the sulfur seems to dominate.
A facile approach to an optically active tetracyclic intermediate for the synthesis of 6‐methyl‐19‐norsteroids
Authors: Pandit U.K. , Bieräugel H.
Published: September 2010

The asymmetric synthesis of (‐)‐(13S, 17S)‐6‐methyl‐17β‐acetoxy‐13,14‐dehydroequilinin methyl ether is described.
Stereochemistry of cyclopropane ring hydrogenolysis
Authors: Kieboom A.P.G. , van Benschop H.J. , van Bekkum H.
Published: September 2010

The hydrogenolysis of cis‐1,2‐dimethyl‐1,2‐diphenylcyclopropane (cis‐1) has been studied using palladium, platinum, rhodium and Raney‐nickel as catalysts. The stereoselectivity towards suprafacial hydrogen addition to the C(1)−C(2) bond is higher than that for the corresponding trans‐compound (trans‐1), whereas the stereochemistry of the reaction of cis‐1 on palladium is not influenced by strong acids (in contrast to trans‐1).

The different behaviour is explained in terms of serious steric repulsion of intermediate species and points to the occurrence of a protonated cyclopropane species in the hydrogenolysis of trans‐1 in acidic medium.
Addition of hydrogen chloride to 1,2,3‐pentatriene
Authors: Mirejovsky D. , Arens J.F. , Drenth W.
Published: September 2010

The addition of HCl to 1,2,3‐pentatriene has been studied in 95 vol. % aqueous ethanol containing 4−10 mol/1 HCl. The reaction involves rate‐determining proton attack at the terminal methylene group with formation of 1,2‐ and 1,4‐adducts. Subsequently, the 1,2‐adduct is converted into a di‐adduct. The reaction shows pseudo‐first‐order kinetics. Log k1 is linear in H0 with a slope equal to −1.18 ± 0.01. The average value of the kinetic isotope effect kH/kD is 1.7. A change in nucleophile (ClO4−, SO24−, Br−) does not affect the rate. The addition of HCl is a two‐step process with a carbocation intermediate. In all probability, alcohol and water are not covalently present in the transition state of the rate‐determining step.
Vinyl copper(I) compounds: Part II: Stereospecific addition of homocuprates to 1‐alkynes in tetrahydrofuran
Authors: Westmijze H. , Meijer J. , Bos H.J.T. , Vermeer P.
Published: September 2010

Homocuprates [RCuR”]MgX, 1 (R = alkyl; R” = R or BuC≡C) appeared to be useful reagents for the introduction of an R group into 1‐alkynes R′−C≡C−H 2 (R′ = Ph, H, alkyl) in tetrahydrofuran as a solvent. Depending on R and R′ terminal alkenes RR′CCH2 4a, non‐terminal alkenes E−R′CHCHR 4b or mixtures of 4a and 4b were isolated after protic work‐up. Except for the reaction of t‐Bu2CuMgCl with Ph−C≡C−H and t‐Bu−C≡C−H only cis additions were observed.

In two cases, viz. for the reaction of Me2CuMgCl and t‐Bu2CuMgCl with Ph−C≡C−H, evidence was obtained for accompanying proton abstraction from the terminal alkyne 2 by the cuprate. This proton abstraction could be suppressed completely by carrying out the addition in the presence of LiBr. Moreover, a strong accelerating influence of LiBr on the rate of the R transfer from the cuprate 1 to the 1‐alkyne 2 was observed.
C‐nitroso compounds. Part XXVII. The lability of chlorine in (1‐chloroalkyl)nitroxides. Reaction with tri‐n‐butyltin hydride and nitric oxide
Authors: Kayen A. H. M. , de Boer K. , de Boer Th. J.
Published: September 2010

(1‐Chloroalkyl)nitroxides1(Table I) are converted by tri‐n‐butyltin hydride into halogenfree nitroxides3(Table II)viaintermediate nitrones2(reactions [6], [7]). This provides a direct method to generate non‐symmetrical di‐sec‐alkylnitroxides5afrom chloro nitroso compounds andsec‐halides by the action of tributyltin hydride (reaction [5]).

Assisted by the presence of an external radical X•, (1‐chloroalkyl)nitroxides1can lose chlorinehomolyticallyto yield a nitrone (reaction [11]) in a process, which is reversible if the X‐Cl bond is weak.

The mechanism of interference of NO as an external radical is discussed in view of its essential role in the photolysis ofgem‐chloro‐nitroso compounds which proceedsvia(1‐chloroalkyl)nitroxides1. These nitroxides undergo C‐Cl homolysis in most solvents; in alcoholic solventsheterolyticloss of chlorine (reactions [13]‐[15]) cannot be excluded when NO is present.

(1‐Chloroalkyl)nitroxides1may also decompose thermally into a chloro nitroso compound and a chloroalkyl radical by α‐cleavage of either of the two C‐N bonds.
C‐nitroso compounds. Part XXIX. The photo‐oxidation of monomeric aliphatic nitroso compounds
Authors: Broekhoven F. J. G. , Bolsman Th. A. B. M. , de Boer Th. J.
Published: September 2010

Molecular oxygen does not attack 2‐methyl‐2‐nitrosopropane (t‐BuNO) in the dark, but by irradiating solutions in benzene with light of 500‐700 nm, it gives tert‐butyl nitrate in yields up to 70%, provided oxygen is present in large excess. The mechanism involves tert‐butyl radicals and NO, formed upon primary photodissociation. Oxygen attacks both, but t‐Bu• much faster than NO, and consequently there is preferential t‐BuOO• radical formation. Its further reaction with NO leads to the nitrate, possibly via a highly unstable peroxy nitrite (t‐BuOONO). All by‐products (t‐BuNO2, t‐BuONO, t‐BuOH, isobutene) are readily explained with the same initial dissociation mechanism. No evidence was found for a route to t‐BuNO2 via an adduct between oxygen and the excited nitroso compound, as postulated earlier.

The influence of DBMP (2,6‐di‐tert‐butyl‐4‐methylphenol) ‐ a t‐BuOO• and NO2 scavenger ‐ on the product distribution agrees with the overall mechanism.
Thermolysis of manganese(III) acetate in acetic anhydride and in acetic anhydride/acetic acid mixtures
Authors: de Klein W. J.
Published: September 2010

The thermolysis of manganese(III) acetate in acetic anhydride/acetic acid mixtures has been studied. In acetic anhydride succinic anhydride is the main reaction product with acetoxyacetic acid the main side product. In acetic acid the reverse situation is met CO2 is scarcely evolved, therefore intermediate formation of acetoxy radicals can only be a minor reaction. The manganese(III) acetate reduction in acetic anhydride is zero order in Mn(III). The reaction is catalyzed by acids and base. The enolisation of acetic anhydride is assumed to be the rate determining step. Acetoxyacetic acid and succinic acid originate from oxidation and dimerisation respectively, of carboxymethyl radicals produced from the enol and Mn(III) acetate. An activation energy of Ea = 26.8 kcal mole–1 is found thermolysis of manganese(III) acetate in pure acetic anhydride.
The determination of the stability constants of the complexes of silver(I) with pyridine and with pyrazole in aqueous solution
Authors: Padmos J. , Merman K. J.
Published: September 2010

Stability constants were determined by potentiometric measurements in concentration cells. In aqueous solution at 25° and μ = 0.1, we found

magnified image

In the calculations so‐called corresponding solutions have been used.
Vapour phase iodination of benzene derivatives. Formation of aryl iodides from bromides based on halogen exchange with iodobenzene
Authors: Vonk W. F. M. , Louw R.
Published: September 2010

Unlike chlorination or bromination, direct gas‐phase iodination ArH → ArI is unpractically slow even at 500°. Chloro‐ and bromobenzenes, however, are converted into their iodo analogues. The rather rapid and selective reaction with bromobenzenes lead to exchange equilibria Ar′Br + ArI ⇌ Ar′I + ArBr at a temperature ≥400°. Using iodobenzene as reagent, this process can be used for preparing aryl iodides in high yields.
Dihalogeno(N,N‐diethyldithiocarbamato)‐arsenic(III), ‐antimony(III) and ‐bismuth(III)
Authors: Cras J. A. , van De Leemput P. J. H. A. M. , Willemse J. , Bosnian W. P.
Published: September 2010

The preparation and some physical measurements of a new class of group Vb dithiocarbamato compounds X2M(Et2dtc) (X = Cl, Br, I; M = As, Sb, Bi; Et2dtc = SC(S)NEt2) is reported. The crystal structure of Br2As(Et2dtc) is determined to a conventional R value of 0.05. The compound, crystallizing in the monoclinic space group P21/c with a = 6.407(2), b = 19.054(8), c = 9.405(4)Å, β = 104.0(2)° and Z = 4, is dimeric with two halogen bridges between 5‐coordinated As centres, the dtc ligands being bidentate. The coordination symmetry of the As is due to the stereochemical active lone electron pair as in IF5.
Recueil des Travaux Chimiques des Pays‐Bas Journal of the Royal Netherlands Chemical Society: General method for the synthesis of 3′,5′‐diesters and 2′‐acetals of the four common nucleosides
Authors: van Boom J. H. , Burgers P. M. J. , Haasnoot C. A. G. , Reese C. B.
Published: September 2010

A procedure suitable for the preparation on a large scale of 5′‐O‐(methoxyacetyl)‐3′‐O‐propionylribonucleosides (9a‐d) from each of the four main ribonucleosides 6a‐d has been developed. The usefulness of 9a‐d as starting products for the synthesis of crystalline 2′‐O‐(methoxytetrahydropyranyl)‐ribonucleosides (11a‐d), which are key intermediates in the synthesis of oligoribonucleotides, has been demonstrated.