bluuebunny/crossref_metadata_2025_split huggingface dataset:
The chemistry of small‐ring compounds. Part 47. Small‐ring interference in the ozonolysis of cyclopropylidenecycloalkanes
Authors: van den Heuvel C. J. M. , Holland A. , van Velzen J. C. , Steinberg H. , de Boer Th. J. 
Published: September 2010

AbstractOzonolysis of olefins Ia‐c containing a cyclopropylidene group, does not follow the classical Criegee mechanism but gives the anomalous products IIa‐c, IIIa‐c,IVa‐c and Va‐c, as outlined in Scheme 2. None of these oxidation products contains the cyclopropyl ring any more. It is suggested that primary ozonides containing a cyclopropyl moiety, undergo already at low temperature simultaneous 0–0 homolysis and small‐ring fission, thus generating the key intermediate 1, 6‐biradical X (Scheme 4). This is at the same time a peroxy and a carbon radical, which upon combination – in casu cyclisation – gives the six‐membered peroxa‐ketone II. Apart from combination, biradical X can also undergo intramolecular disproportionation to the unsaturated ketone XIX (Scheme 8) containing a terminal hydroperoxy function. This product does not accumulate as such, but is further oxidised to the epoxide Va‐c with simultaneous formation of the five‐membered cyclic 1, 3‐oxa‐ketone IIIa‐c (cf Scheme 8). The least oxygen‐rich reaction product is the cyclobutanone IV, for which zwitter ion XIV or its ring‐expanded isomer XV (Scheme 6) is a likely precursor.Interception of the first zwitter ion by methanol, followed by loss of oxygen, explains the formation of glycol derivatives VI (Scheme 6). Direct attack of XVIII (Scheme 8) on starting material, provides an other route towards the cyclobutanone IV, which is suppressed in the presence of diphenyl sulfide and cinnamic ester.
Electrical properties of a molecular ion channel
Authors: van der Linden J. H. , Nolte R. J. M. , Drenth W. , Schoonman J. 
Published: September 2010

AbstractA. c. and d. c. electrical conductivities have been determined for complexes of either KCl or K picrate with a polymer of an isocyanide containing benzo‐18‐crown‐6 rings. In both complexes, mixed ionic conductivity occurs. In the KCl complex, chloride ion conductivity predominates. The K‐picrate complex has a low bulk ionic conductivity, but a substantial contribution of cations. The role played by anion‐size effects is discussed.
Behaviour of poly(pyrrole) and poly(N‐methylpyrrole) electrodes in acetonitrile
Authors: Jakobs R. C. M. , Janssen L. J. J. , Barendrecht E. 
Published: September 2010

AbstractThe impedance of poly(pyrrole) (PP) and poly(N‐methylpyrrole) (PMP) films on platinum in an acetonitrile, LiClO4 solution has been measured. At potentials more positive than a characteristic value, the electrodes exhibit porous behaviour and the impedance is determined by the double‐layer capacitance and the solution resistance inside the pores. At more negative potentials, the PP and PMP electrodes behave like flat‐plate electrodes and two impedance contributions can be distinguished, i.e. a material contribution (material resistance and material capacitance) and a contribution from the interphase polymer‐electrolyte (faradaic resistance and double‐layer capacitance).
Enamine synthesis using the Horner‐Wittig reaction. Part 1. (Aminomethyl)diphenylphosphine oxides, new formyl anion equivalents
Authors: Broekhof N. L. J. M. , van der Gen A. 
Published: September 2010

AbstractUsing the Horner‐Wittig reagent (morpholinomethyl)diphenylphosphine oxide (7), aromatic, aliphatic and α, β‐unsaturated aldehydes are converted into morpholino enamines of their homologous aldehydes. With [(N‐methylanilino)methyl]diphenylphosphine oxide (12), the same aldehydes, together with the ketones (cyclic as well as acyclic, both saturated and α, β‐unsaturated), are converted into enamines of their homologous aldehydes. Both types of enamines are converted into the corresponding aldehydes by mild, acid‐catalyzed hydrolysis, showing the utility of 7 and 12, as formyl anion equivalents. Preparation of each geometrical isomer of the N‐methylanilino enamines is possible since the intermediate diastereoisomeric adducts 13 can be separated.
C‐Nitroso compounds. Part XXXVI. Rearrangement of 2‐chloro‐2‐nitrosofenchane and 2‐chloro‐2‐nitrosocamphane
Authors: Lub J. , de Boer Th. J. 
Published: September 2010

Abstract2‐Chloro‐2‐nitrosofenchane 7 rearranges under the influence of aluminium chloride to the isomeric chloronitrones 9 and 12 (Scheme 3). 2‐Chloro‐2‐nitrosocamphane 18 (Scheme 4) gives, under similar conditions, only one chloronitrone 19, despite the close structural relationship between the starting materials 7 and 18. The chloronitrones react with all common nucleophiles, e.g. with water, to give hydroxamic acids, which can easily be reduced to the amides 4, 5 and 6. The first and last of these amides are not accessible by Beckmann rearrangement of the appropriate oximes.
The influence of substituents on the geometry of the cyclopropane ring. I. The crystal and molecular structure of cyanocyclopropane at −85°C. Film and diffractometer measurements
Authors: Kiers C. TH. , de Boer J. S. A. M. , Heijdenrijk D. , Stam C. H. , Schenk H. 
Published: September 2010

AbstractCrystals of cyanocyclopropane have been grown from liquid. At −85°C, cell parameters are a = 7.244(5), b = 7.821(2), c = 6.916(3) Å in the orthorhombic space group Pnma with Z = 4. Intensity data were collected in three different ways, viz. photographically using rotation and Weissenberg techniques and electronically by means of a diffractometer. Within the limits of accuracy, the three data sets result in equal bond lengths and angles. The most important result from the structure determination is the difference of 0.033 Å between the lengths of the distal and vicinal ring bonds, which had not previously been measured directly from X‐ray experiments.
3,4‐Dihydro‐2,2′‐pyrromethen‐5(IH)‐ones ; Synthesis and photochemical reactivity
Authors: Koek J. H. , Lugtenburg J. 
Published: September 2010

AbstractFour isomeric 3,4‐dihydro‐2,2′‐pyrromethen‐5(1H)‐one E/Z pairs were prepared which show not only a photochemical E/Z isomerization but also a photo‐Fries type rearrangement.
Cycloaddition of substituted cyclopropyl ethers to tetracyanoethene
Authors: Wiering P. G. , Steinberg H. 
Published: September 2010

AbstractThe cyclopropyl methyl ethers 2–4, 14 and 15 and tetracyanoethene (TCNE) give, in a multistep cycloaddition, the 1,1,2,2,‐cyclopentanetetracarbonitriles 5–8, 16 and 17. It has been established that the cycloaddition reactions take place with inversion of configuration of the cyclopropyl C2 (or C3) carbon atom and racemization at the C1 carbon atom. In the presence of methanol, the all‐cis‐2,3‐dimethylcyclopropyl methyl ether 3 and TCNE give, in a slow reaction, a mixture of cycloadducts 7 and 8, together with the ring‐opened tetracyanopentanone acetal 13, whereas the phenyl‐substituted cyclopropyl ethers 14 and 15 yield exclusively, and relatively rapidly, the corresponding acetal 19. These results strongly indicate that the reaction proceeds via zwitter‐ions which are formed by SH2‐type attack of TCNE anion radicals on the cyclopropane ring.
Isomeric C5H9O− ions formed in gas‐phase reactions of anions with 2,2‐dimethylpropanal and 2,2‐dimethylcyclopropanol
Authors: Peerboom Renée , Ingemann Steen , Nibbering Nico M. M. 
Published: September 2010

AbstractFourier‐Transform Ion‐Cyclotron‐Resonance (FT‐ICR) mass spectrometry has been used to investigate proton abstraction from 2,2‐dimethylpropanal (1) and 2,2‐dimethylcyclopropanol (2) in the gas‐phase. The structures of the C5H9O− ions formed have been probed by studying their reactions with various molecules. The C5H9O− ions derived from 1 and 2 are observed to undergo hydrogen‐deuterium exchange with D2O and to react with C6F6 in a similar way. The results are discussed in terms of five possible structures for the C5H9O− ions: (CH3)3CC̄O (a) magnified image
Photochemistry of dienones. Part 141. The photochemistry of some 9‐demethylated ionyl and ionylidene compounds; a search for, and an example of, η‐hydrogen abstraction
Authors: Visser Cornelis P. , Cerfontain Hans , Geenevasen Jan A. J. , Jorritsma Ruurd 
Published: September 2010

AbstractThe photochemical reactions of some (9‐demethylionyl)‐ and (9‐demethylionylidene)acetones and the corresponding acetophenones have been studied. The β‐isomers 1a and 1b, both under direct and triplet‐sensitized irradiation, undergo (E) ‐ (Z) isomerization of the 7,8‐double bond as the only observed reaction; with 1a, the (E) ‐ (Z) isomerization is followed by a thermal 6e‐electrocyclization with formation of 6. The α‐isomer 2 undergoes (E) ‐ (Z) isomerization both around the 7,8‐ and the 9,10‐double bond.The aliphatic β‐ionyl ketone 3a, upon irradiation with λ 254 nm, undergoes a sigmatropic [1,5]‐hydrogen shift with formation of the retro‐isomer 9, which, upon electronic excitation, undergoes a Norrish‐type‐II γ‐hydrogen abstraction with formation of the triene 12. The related benzoyl ester 4, upon λ 254 nm excitation, also exhibits the [1,5]‐hydrogen shift with formation of the photostable retro‐isomer 17. Upon (n‐π*) excitation of the aromatic β‐ionyl ketone 3b with λ 350 nm, the triene 12 and acetophenone are formed as primary photoproducts. This photoconversion constitutes the first example of η‐hydrogen abstraction by a benzoyl chromophore directly leading to products by β‐scission of the resulting 1,8‐biradical.
Photochemical conversion of norbornadiene into quadricyclane in the presence of acridinone‐type sensitizers
Authors: Tinnemans A. H. A. , den Ouden B. , Mackor A. , Bos H. J. T. 
Published: September 2010

AbstractIn this study, a series of acridinones and benzo‐fused acridinones have been used for the first time as efficient photosensitizers for the norbornadiene‐quadricyclane isomerization by near UV and visible iradiation. Their triplet energies (240‐280 kJ · Mol−1) are well below the value of 290 kJ · Mol−1 which is generally assumed for norbornadiene. A mechanism is postulated involving an exciplex between sensitizer and norbornadiene.Limiting quantum yields of 0.5 and higher have been determined for this valence isomerization extrapolated to infinite norbornadiene concentration.Exciplex formation is supported by measurements of the rate of constant k2 for quenching of excited sensitizer by norbornadiene, yielding values which are much smaller than the diffusion‐controlled quenching constant.
Ar(alk)ylsulfonyl ethyl groups as phosphorus‐protecting functions
Authors: Claesen C. A. A. , Segers R. P. A. M. , Tesser G. I. 
Published: September 2010

AbstractVarious 2‐[Ar(alk)ylsulfonyl]ethanols were prepared and subsequently converted into the corresponding phosphorodichloridites in almost quantitative yield via a convenient synthetic route. The versatility of the method, which obviates the necessity of a distillation step, is demonstrated by the preparation of other Ar(alk)yl phosphorodichloridites, including the unstable benzyl phosphorodichloridite.
A comparison of β‐functionalized ethyl groups for the protection of the phospho function in decathymidylate synthesis using a phosphite triester approach
Authors: Claesen C. A. A. , Segers R. P. A. M. , Tesser G. I. 
Published: September 2010

AbstractA number of phosphorodichloridites (1) carrying various β‐functionalized ethyl protective groups were converted into their corresponding phosphoromorpholido chloridites (2). These were then reacted with 5′‐O‐(dimethoxytrityl)thymidine to give the pertinent phosphoromorpholidites (3). The applicability of these compounds in the synthesis of oligodeoxynucleotides on a solid support has been evaluated using the synthesis of the thymidine decamer.
Réactions d'addition nucléophile sur les cétones dépendence conformationnelle de l'effet isotopique
Authors: Boyer B. , Lamaty G. 
Published: September 2010

AbstractIn the present investigation, we have measured the secondary deuterium isotope effects in borohydride addition reaction for a serie of cyclohexanones, both hindered and unhindered. We observed an inverse isotope effect, kH/kD < 1.00 for those ketones; these inversions of the isotope effects are discussed in terms of torsional effects and hyperconjugative factor.
Dimetallation of phenylacetylene. Synthesis of ortho‐substituted derivatives of phenylacetylene, benzo[b]selenophene and benzo[b]tellurophene
Authors: Brandsma L. , Hommes H. , Verkruijsse H. D. , de Jong R. L. P. 
Published: September 2010

AbstractPhenylacetylene can be dimetallated in two ways. o‐K‐C6H4‐C  C ‐ Li is formed by treating phenylacetylene at −70°C with two equivalents of butyllithium and one equivalent of potassium tert‐butoxide in a mixture of tetrahydrofuran and hexane. The dimetallation with BuLi‐N,N,N′, N′‐tetramethylethanediamine (TMEDA) affords a mixture of about 15% (m + p)‐Li‐C6H4‐C  C
Li and 85% o‐Li‐C6H4‐C  C‐Li. Ortho‐K‐C6H4‐C  C‐Li can be transformed into the dilithio or di‐Grignard derivatives by addition of anhydrous lithium bromide or magnesium bromide etherate. Reaction of the dilithio derivative with elemental selenium and tellurium, followed by successive addition of tert‐butyl alcohol and hexamethylphosphoric triamde (HMPT), gives benzo[b]selenophene and benzo[b]tellurophene in good yields.Regiospecific functionalization of the nucleus via dimetal derivatives succeeds in the case of alkylation, halogenation, sulfenylation and acylation (with dimethylformamide and dimethylacetamide). Trimethylchlorosilane, chloromethyl methyl ether, aldehydes and ketones do not however react regiospecifically.
Synthesis of 16α‐ethyl‐21‐hydroxy‐19‐norpregn‐4‐ene‐3,20‐dione (Org 2058)
Authors: Zeelen F. J. , van den Broek A. J. 
Published: September 2010

AbstractThe syntheses of the title compound and of some ester derivatives are described. These norprogesterone derivatives show interesting progestational activities.
Synthesis and folded conformation of some 5,15‐diaryloctamethylporphyrins with a sulfonyloxy group in the aryl part
Authors: Sanders G. M. , van Dijk M. , Koning G. P. , van Veldhuizen A. , van der Plae H. C. 
Published: September 2010

AbstractThe porphyrins 1a‐g were synthesized. In CDCl3 solution 1a and 1b occur to an important extent in a folded conformation, as is indicated by an upfield shift of 2‐3 ppm for the tosylprotons in the 1H NMR spectrum. For compounds with longer chains or an ester instead of a sulfonyloxy group the upfield shift is much smaller.
Reduction of unsaturated β‐oxo esters: Synthesis of unsaturated β‐hydroxy esters and of unsaturated 1,3‐diols
Authors: van den Goorbergh J. A. M. , Nonneman L. E. Y. , van der Gen A. 
Published: September 2010

AbstractThe β‐carbonyl group of the unsaturated β‐oxo esters 1 and 2 can be selectively reduced using sodium tetrahydroborate in methanol to give the γ‐ and δ‐unsaturated β‐hydroxy esters 3 and 4, respectively. The unsaturated 1,3‐diols 5 and 6 were obtained by reduction of the β‐carbonyl group as well as the ester function of unsaturated β‐oxo esters 1 and 2 using lithium tetrahydroaluminate. For the conversion of γ‐unsaturated β‐oxo esters 1, with R1 = H and R2 = aryl, into the corresponding unsaturated diols 5, hydrobis(2‐methylpropyl)aluminum was used to prevent reduction of the double bond.
Synthesis of 5‐, 6‐, 7‐ and 18‐mono‐13C‐labelled retinals
Authors: Courtin J. M. L. , Lam G. K.'T , Peters A. J. M. , Lugtenburg J. 
Published: September 2010

AbstractFour retinals labelled at positions 5, 6, 7 and 18 with 13C were obtained via simple schemes involving only a few steps with > 98% chemical purity and 92% 13C incorporation. (5‐13C)Retinal was obtained in 26% yield from K13CN. (6‐13C)‐ and (7‐13C)Retinal were obtained in 37% yield from (2‐13C)‐ and (1‐13C)acetonitrile, respectively, while (18‐13C)retinal was obtained in 8 steps and 4% yield starting from 13CH3I. Their 13C‐ 1H and 13C‐ 13C NMR coupling constants were determined.
A novel water‐soluble fluorescent probe: Synthesis, luminescence and biological properties of the sodium salt of the 4‐sulfonato‐3,3′,5,5′‐tetramethyl‐2,2′‐pyrromethen‐1,1′‐BF2 complex
Authors: Wories H. J. , Koek J. H. , Lodder G. , Lugtenburg J. , Fokkens R. , Driessen O. , Mohn G. R. 
Published: September 2010

AbstractThe reaction of the 3,3′,5,5′‐tetramethyl‐2,2′‐pyrromethen‐1,1′‐BF2 complex with chlorosulfonic acid and its subsequent neutralisation with sodium bicarbonate yields the titled compound 1, which, in addition to appropriate thermal and photochemical stability, possesses excellent fluorescent properties. As a preliminary assay of its potential usefulness as a fluorescent probe in medical and biological research, the chemical was administered intravenously to rats and possible signs of toxicity were recorded. The rats showed no apparent detrimental effects and excreted the compound in the urine within three hours. In tests in which Salmonella and E. coli strains were used as indicators of genotoxicity, no mutagenic effects were observed.
Reductive introduction and oxidative removal of the 4‐methoxybenzyl ether in the presence of the azido group. Synthesis of 2‐azido‐2‐deoxy sugars having chain extension at C‐4
Authors: Kloosterman M. , Kuyl‐Yeheskiely E. , van Boom J. H. 
Published: September 2010

Abstract3,4,6‐Tri‐O‐acetyl‐2‐azido‐2‐deoxy‐α‐D‐glucopyranosyl bromide was converted in four steps into allyl 2‐azido‐3‐O‐benzoyl‐2‐deoxy‐4,6‐O‐(4‐methoxybenzylidene)‐β‐D‐glucopyranoside. Treatment of the latter with sodium cyanoborohydride and hydrogen chloride in oxolane (THF) gave allyl 2‐azido‐3‐O‐benzoyl‐2‐deoxy‐6‐O‐(4‐methoxybenzyl)‐(β‐D‐glucopyranoside. Further, 3,4,6‐tri‐O‐acetyl‐2‐azido‐2‐deoxy‐α‐D‐galactopyranosyl bromide was converted in five steps into allyl 2‐azido‐3‐O‐benzoyl‐2‐deoxy‐6‐O‐(4‐methoxybenzyl)‐β‐D galactopyranoside. The 4‐methoxybenzyl ether could be removed in the presence of the azido function using 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ).
The preparation of 1‐aminopurinium mesitylenesulfonates by reaction of purines with O‐(mesitylenesulfonyl)hydroxylamine
Authors: Kos N. J. , Jongejan H. , van der Plas H. C. , van Veldhuizen A. 
Published: September 2010

AbstractA number of 1‐aminopurinium mesitylenesulfonates have been prepared in reasonable to good yields by treatment of the corresponding purines with O‐(mesitylenesulfonyl)hydroxylamine. The structure of these salts has been established by means of 1H and 13C NMR spectroscopy, using, as diagnostic tools, the J(H‐2, H‐6), 3J(C‐2, H‐6) and 3J(C‐6, H‐2) coupling constants for compounds which are unsubstituted at positions 2 and 6 and the 13C Δδ values of C‐2 or C‐6 and C‐8 for C‐2 or C‐6 substituted purinium salts.
The chemistry of small‐ring compounds. Part 49. A route to oxaspiropentanes, undisturbed by rearrangement
Authors: Hofland A. , Steinberg H. , de Boer Th. J. 
Published: September 2010

AbstractThe title compounds have been prepared in 70‐90% yield by epoxidation of appropriate cyclopropylidene compounds with KHSO5 in a phosphate buffer in the presence of acetone. The latter is converted into an unstable dioxirane, which acts as the oxygen‐transferring agent.
Synthesis of some modified 2′‐5′‐linked oligoriboadenylates of 2‐5A core
Authors: Visser G. M. , Tromp M. , van Westrenen J. , Schipperus O. , van Boom J. H. 
Published: September 2010

AbstractThe synthesis of three analogues of 2′‐5′‐linked oligoriboadenylates is reported. Two trimers, having at the 2′‐end a 3′‐amino‐ (or 3′‐tetradecanamido)‐3′‐deoxy‐riboadenosine, were assembled via a phosphotriester approach. In the same way, we also prepared a tetramer carrying at the 2′‐end β‐L‐riboadenosine instead of β‐D‐riboadenosine. The non‐terminal building unit 3′,5′‐O‐(tetraisopropyldisiloxane‐1,3‐diyl)‐N6‐benzoyladenosine and the appropriately protected modified riboadenosines were coupled using the phosphorylating agent 2‐chlorophenyl‐O,O‐bis(1‐benzotriazolyl) phosphate. The removal of all protecting groups from the intermediate trimers and tetramer was effected by ammonolysis, followed by treatment with fluoride ions.
Synthesis of retinals isotopically labelled at positions 11, 12, 14 and 20
Authors: Pardoen J. A. , van den Berg E. M. M. , Winkel C. , Lugtenburg J. 
Published: September 2010

AbstractFive retinals, having different combinations of 2H, with one having 2H and 13C labels at positions 11, 12, 14 and 20, were obtained with a chemical purity of above 98%, a level of 2H enrichment greater than 95% and with 13C enrichment of 99%. The retinals concerned are (20,20,20‐2H3)‐, (12,20,20,20‐2H4)‐, (12,14,20,20,20‐2H5)‐, (11,14‐2H2)‐, (12,14‐2H2)‐ and (12,14‐2H2,20‐13C)retinal.
Chemistry of four‐membered cyclic nitrones. Reaction with a non‐nucleophilic base: Stereoselective ring opening of in situ generated 1,2‐dihydroazetes and structure elucidation of the resulting α,β‐unsaturated oximes by X‐ray analysis
Authors: van Eijk Peter J. S. S. , Reinhoudt David N. , Harkema Sybolt , Visser Richard 
Published: September 2010

AbstractThe four‐membered cyclic nitrones (2,3‐dihydroazete 1‐oxides) 1a‐g isomerize to the corresponding oximes 3 and 4 on treatment with potassium tert‐butoxide. In N,N‐dimethylformamide at room temperature, oxime 4 is formed preferentially; in tetrahydrofuran, both the oximes 3 and 4 are formed. The oximes 3c‐e are converted into the corresponding 6H‐1,2‐oxazin‐6‐ones 5c‐e by reaction in acetic acid. The oxime 4a has the (E,E) stereochemistry and the O‐benzoyl derivative of 3b (6) the (Z,E) stereochemistry, as shown by X‐ray analysis. In solution, NOE difference spectroscopy indicates the (Z,E) and (E,E) configuration for 3a and 4a, respectively. The α,β‐unsaturated ketone (Z)‐8 was prepared by reaction of (Z,E)‐3b with bispyridine silver permanganate. Reaction of (Z)‐8 with hydroxylamine in pyridine yields (Z,E)‐3b and the 6H‐1,2‐oxazin‐6‐one 5b, which is formed by rapid cyclization of (Z,Z)‐3b.The conversion of nitrones 1 into the corresponding oximes 3 and 4 is explained in terms of an electrocyclic ring opening of an intermediate N‐hydroxy‐1,2‐dihydroazete. In this electrocyclic reaction, a strong preference for outward rotation of the hydroxy group is observed.
Energy migration in rare‐earth compounds
Authors: Blasse G. 
Published: September 2010

AbstractThe luminescence processes in several rare‐earth compounds are discussed, viz. sensitization, one‐step energy transfer, multi‐step energy transfer (migration) and trapping. Results are given for compounds containing Eu3 +, Tb3+ and Gd3+. The dimensionality of the rare‐earth sublattice (three, two or one) influences the migration and examples are presented. The case of Eu3+ is the first for which one‐, two‐ and three‐dimensional migration has been observed for one and the same optically active ion. Gadolinium compounds can be applied in luminescent lamps, where they improve the lamp output considerably.