bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemistry of crown ethers (XVI). A safe and efficient procedure for the isolation and purification of crown ethers by complex formation with alkaline earth metal alkanedisulfonates
Authors: de Jong F. , Reinhoudt D. N. , van Zon A. , Torny G. J. , van de Vondervoort E. M.
Published: September 2010

A safe, efficient and selective method has been developed for the isolation and purification of crown ethers to replace the conventional procedure, which involves repeated vacuum distillations and has reportedly led to destructive explosions. The method is based on the formation of an insoluble 1:1 complex upon stirring a solution of a crown ether in an organic solvent with solid metal salts of 1,n‐alkanedisulfonic acids, such as barium and strontium methanedisulfonate and barium 1,2‐ethanedisulfonate. This extraction procedure can be applied to several crown ethers (including 18‐crown‐6) dissolved in a variety of solvents. Almost quantitative recovery of the crown ether is achieved by continuous extraction with nitromethane.

The usefulness of the method was illustrated by isolating 18‐crown‐6 from the crude mixture obtained in the course of its preparation. Whereas conventional workup (including two distillation steps) gave a 25% yield of pure 18‐crown‐6, the CH2(SO3)2Ba‐based method gave a yield of 34%.
Conversion of sterically hindered phenols into the corresponding N,N‐dimethylarenesulfonamides via the Newman‐Kwart rearrangement
Authors: Wagenaar Anno , Engberts Jan B. F. N.
Published: September 2010

The 2‐alkyl‐ and 2,6‐dialkylbenzenesulfonyl chlorides 5a‐f were obtained in high yield by chlorination of the correspondingly substituted S‐aryl N,N‐dialkylthiocarbamates 4a‐g. These precursors have been synthesized via the Newman‐Kwart rearrangement of the corresponding O‐aryl N,N‐dialkylthiocarbamates 3a‐g, which are easily prepared from the sterically hindered phenols 1a‐g. The sulfonyl chlorides 5a‐f are readily transformed into the desired 2‐alkyl‐ and 2,6‐dialkyl‐N,N‐dimethylbenzenesulfonamides 6a‐f.
Preparation of deuterium‐labelled retinals having high deuterium content on specific positions 10‐Mono‐, 11‐mono‐, 10,11‐di‐ and 14,20,20,20‐tetradeuterioretinal
Authors: Broek A. D. , Lugtenburg J.
Published: September 2010

10‐Mono‐, 11‐mono‐ and 10,11‐dideuterioretinal (in the all‐trans, 9‐cis, 11‐cis and 13‐cis forms) of > 98% purity and the required (> 96%) deuterium incorporation were prepared via LiAlH4 or LiAlD4 reduction of the retinylidene derivative 8. Compound 8 was prepared by coupling β‐ionone with 6,6‐dimethoxy‐4‐methyl‐3‐hexen‐1‐yne (6), which had been obtained in high yield from 2‐propynyl bromide and commercial 4,4‐dimethoxy‐2‐butanone (4). Exchange of 4 with D2O and base gave 4,4‐dimethoxy‐1,1,1,3,3‐pentadeuterio‐2‐butanone (4a), which in turn, using the same synthetic method, finally provided 14,20,20,20‐tetradeuterioretinal.
Biomimetic total synthesis of steroids VI. Stereospecific synthesis of 19‐nor‐8α‐steroids and 11α‐alkyl derivatives
Authors: Groen M. B. , Hindriksen B. , Zeelen F. J.
Published: September 2010

Cationic cyclization of 2‐[6‐(3‐methoxyphenyl)‐(Z)‐3‐hexenyl]‐3‐methyl‐2‐cyclopentenol (7a) produced 1‐ and 3‐methoxy‐17‐methyl‐8α‐gona‐1,3,5(10),13(17)‐tetraene (8a and 9a) with complete stereospecificity. Cyclization of similar substrates with an alkyl substituent in the appropriate position gave exclusively 11α‐alkyl derivatives of 8a and 9a. The products were converted into the corresponding 13α,17α‐epoxides by peracid oxidation and hence into derivatives of 8α‐estrone and 8α‐estradiol. 11α‐Methyl‐8α‐estra‐1,3,5(10)‐triene‐3,17(3‐diol (16b) was obtained in its two enantiomeric forms via resolution of its 3‐methyl ether.
Short‐range structure determination by EXAFS spectroscopy: Theory, experimental technique and spectral analysis
Authors: Vlaic G. , Bart J. C. J.
Published: September 2010

A physico‐chemical description of the extended X‐ray absorption fine structure (EXAFS) phenomenon is given and experimental methods for its measurement in transmission mode are indicated. Pros and cons of various procedures for careful evaluation of the experimental absorption data are described, which comprise background removal according to Victoreen's relation or by polynomial fitting and criteria for Fourier filtering methods are given. Three different approaches for EXAFS signal analysis are discussed namely fitting with parametrized amplitude and phase functions, comparison of experimental data with theoretical EXAFS spectra and Fourier transform techniques; the limits of applicability of these procedures are indicated. A critical evaluation is given for the various methods for correction of the resulting radial distribution function in order to comply with crystallographic distances. The determination of coordination numbers is discussed and the procedures are illustrated with results for metallic titanium, rutile and anatase.
Synthesis, spectroscopy and polymerization of methyl α‐([13C,15N]isocyano)propionate; acetic formic anhydride as N‐formylating reagent
Authors: Vlietstra Edward J. , Nolte Roeland J. M. , Zwikker Jan W. , Drenth Wiendelt , Jansen Richard H. A. M.
Published: September 2010

Methyl α‐([13C,15N]isocyano)propionate was prepared starting from (±)‐[15N]alanine. The amino acid was converted into the methyl ester, which was formylated with acetic [13C]‐formic anhydride, to afford the methyl ester of N‐[13C]formyl[15N]alanine. Dehydration of the latter compound gave the isocyanide, which was polymerized with nickel chloride. 1H, 13C, 15N NMR and IR data of the labelled compounds are presented.
Coalescence phenomena in the NMR spectra of some cycloheptatrienes
Authors: Zwaard A. W. , Smits H. J. E. , Kloosterziel H.
Published: September 2010

Coalescence phenomena have been observed in the NMR spectra of a variety of 7‐substituted 1,3,5‐cycloheptatrienes upon varying temperature and/or solvent. Using two different methods, the energy of activation of the process responsible for coalescence has been determined. Within a group of structurally similar para‐substituted phenyl sulphides a linear relation has been found between the energy of activation and the acidity constant of the corresponding benzenethiol, suggesting the occurrence of ion pairs. The relatively low energy of activation for the phenyl sulphides, when compared with the values of the phenyl sulphones, may result from the structure of the intermediate ion pairs.

In addition to the above, a different exchange process between cycloheptatrienyl sulphides and tropylium salt via sulphonium ions has been observed.
A simple synthesis of glycino ethyl ester derivatives of hexachlorocyclotriphosphazene
Authors: Smaardijk A. A. , de Ruiter B. , van der Huizen A. A. , van de Grampel J. C.
Published: September 2010

A general method of preparation is described for glycino ethyl ester derivatives of phosphazene‐like ring systems, which may serve as precursors for anti‐cancer drugs.
Intramolecular competition between the di‐π‐methane and the oxa‐di‐π‐methane rearrangements in a triplet‐excited β, γ, β1, γ1‐dienone.
Authors: van der Veen Reinout , Kruk Cornelis , Cerfontain Hans
Published: September 2010

The triplet photosensitization of the β, γ, β1, γ1‐dienone 2 leads to the formation of the DPM isomer 6 and the two ODPM isomers 7 and 8 in a ratio of 35:17:10. This is the first reported example of a substrate which exhibits intramolecular competition as demonstrated by the occurrence of both the DPM and ODPM rearrangement.
The meta‐photocyloaddition of cyclopentene to anisole
Authors: Jans A. W. H. , van Dijk‐Knepper J. J. , Cornelisse J.
Published: September 2010

The meta‐photocycloaddition of cyclopentene to anisole yields the hitherto unknown 1‐methoxy‐exo‐tetracyclo[6.3.0.02,11.03,7 ]undec‐9‐ene together with the endo‐isomer in the ratio 1: 9.3.
The chemistry of small ring compounds. Part 46. Reduction of 1‐halocyclopropyl sulfides by thiolates
Authors: Jorritsma R. , Steinberg H. , de Boer Th. J.
Published: September 2010

The reaction of 1‐halocyclopropyl sulfides with sodium alkanethiolates in protic or aprotic solvents leads to high yields of cyclopropyl sulfides, in which halogen has been replaced by hydrogen. The complementary oxidized product is, in most cases, the thioketone or thioaldehyde derived from the alkanethiolate. The reduction is unaffected by radical scavengers or by oneelectron donors.

Reaction kinetics indicate that the reduction proceeds via the 1‐(alkylthio)cyclopropyl cation. A mechanism is discussed (Scheme 9) in which this ambident cation is attacked by thiolate on sulfur. In the intermediary sulfonium ylid an intramolecular hydrogen shift leads to the observed products.
Protonation, and reductive cleavage by lithium of the CS bond, in (methylthio)pentadienylic anions generated from various cis,trans‐isomers of 1‐(methylthio)‐1,3‐pentadiene and 1‐(methylthio)‐1,4‐pentadiene
Authors: Gräfing R. , George A. V. E. , Brandsma L.
Published: September 2010

Treatment of the various cis,trans‐isomers of CH3SCHCHCHCHCH3 and CH3SCHCHCH2CHCH2 with a slight excess of potassium amide in liquid ammonia, followed by quenching of the solutions thus obtained with ammonium chloride, gives, in all cases, the is isomer CH3SCH2CHCHCHCH2(> 90% trans) From the anionic solutions 1H NMR spectra have been recorded.

Reductive cleavage of the CS bond of the anions CH3SCHCHCHCHCH2⊖ with lithium in liquid ammonia, followed by methylation, leads to almost complete recovery of CH3SCHCHCHCHCH3. During this cleavage, the double bond next to sulfur retains its configuration, while the configuration of the other double bond changes from trans to cis. It remains the same, however, on starting from a (methylthio)pentadiene with a cisC3C4 double bond. The ultimate result of the cleavage procedure with CH3SCHCHCH2CHCH2 is CH3SCHCHCHCHCH3: the configuration of the C1C2 double bond remains the same and the C3C4 double bond is always cis.
Synthesis, characterization and reactivity of boron‐bridged iron(II) dioxime coordination compounds
Authors: Verhage M. , Hoogwater D. A. , van Bekkum H. , Reedijk J.
Published: September 2010

Reaction of iron(II) dioxime compounds with boron trifluoride diethyl etherate gives clathro compounds. When diphenylboron bromide is used as a reagent, boron‐bridged tetragonal dioxime systems can be prepared via a so‐called pre‐clathro intermediate. This intermediate also shows a tendency to rearrange into a clathro compound. The tetragonal boron‐bridged dioxime compounds Fe(DPGBPh2)2(MeIz)2, Fe(DAGBPh2)2(MeIz)2 and Fe(DMGBPh2)2(MeIz)2 have a structure similar to that of the corresponding hydrogen‐bridged compounds, as deduced from their optical spectra — and for the latter compound, as shown by single crystal X‐ray analysis. They are, however, much more stable towards oxidation. The compounds react with both carbon monoxide and benzyl isocyanide. Coordinated carbon monoxide can be removed by irradiation with light.
Ternary complexes of Zn(II), Cd(II), Co(II) and Ni(II) with 2,2′‐bipyridine or 1,10‐phenanthroline and N‐(thiobenzoyyl)‐N‐phenylhydroxylamine
Authors: Thakur R. S. , Mathur S. P. , Sharma B. K.
Published: September 2010

The stability constants of ternary Zn(II), Cd(II), Co(II) or Ni(II) complexes containing 2,2′‐bipyridinyl (Bipy) or 1,10‐phenanthroline (Phen) and N‐(thiobenzoyl)‐N‐phenylhydroxylamine (TBPH) have been determined in 70% (v/v) dioxane/water medium at 30 ± 1°C and at constant ionic strength (0.1 M NaClO4) in a nitrogen atmosphere. A study of the title metal ions in the presence of an equimolar concentration of the two ligands revealed the formation of mixed‐ligand complexes containing a 1:1:1 molar ratio of metal and the two ligands. These ternary complexes are more stable than would be expected on a statistical basis, i.e. the difference, Δlog KM = log Kmamab ‐ log Kmmb, is positive. This is discussed on the basis of π‐acceptor qualities of the heteroaromatic N‐base and the occurrence of a co‐operative effect due to the π systems of two ligands bound to the same metal ion. The trend in stability constants of the mixed‐ligand complexes of the title metal ions is found to be Ni > Co > Cd > Zn. Mixed‐ligand complexes formed with 1,10–phenanthroline are found to be less stable than those formed with 2,2′‐bipyridine and this is discussed on the basis of steric factors.
The role of histidine in the gastrointestinal hormone secretin
Authors: Voskamp D. , Kranenburg P. , Beyerman H. C.
Published: September 2010

Eleven analogues of porcine gut secretin, in which the N‐terminal histidine has been modified or deleted, were prepared and assayed for their potency in stimulating the exocrine pancreatic flow in various animal species. Deletion of the α‐amino group, or replacement of the imidazole by the pyrazole ring, resulted in highly potent analogues. Other alterations destroyed most of the potency. All analogues had immunochemical properties similar to those of porcine gut secretin.
Organometal‐mediated synthesis of conjugated allenynes, allenediynes, vinylallenes and diallenes
Authors: Ruitenberg K. , Kleijn H. , Westmijze H. , Meijer J. , Vermeer P.
Published: September 2010

An extensive study of the reactivity of organometallic reagents R3M (R3 = 1‐alkenyl, 1‐alkynyl, 3‐alken‐1‐ynyl, 1,3‐alkadiynyl or 1,2‐alkadienyl; M = Li, MgCl, ZnCl, Cu, Ag) towards R1R2CCCH‐X (1) and R1R2C(X)‐CCH (4) is described. High yields of R1R2CCCHR3 (2) have been obtained by reaction of 1 (X  Br) with R3‐M (M = MgCl, ZnCl or Cu1/2Li1/2) using Pd[PPh3]4 as catalyst. Similarly, pure 2 have been obtained by the Pd[PPh3]4‐catalyzed reaction of 4 (X = Br, OAc, OS(O)Me, OSO2Me, OP(O)(OEt)2) with R3‐M (M = MgCl, ZnCl, Zn1/2, Cu, Cu1/2Li1/2, Ag, or Ag1/2Li1/2). In some reactions with R3‐Cu, compounds 4 were converted into 2 in the absence of the palladium catalyst.
A molecular cation channel
Authors: van Beijnen A. J. M. , Nolte R. J. M. , Zwikker J. W. , Drenth W.
Published: September 2010

A polymer of an isocyanide, [RNC<]n has been synthesized in which R contains a benzo‐18‐crown‐6 group. The crown ether rings are situated on top of each other and form channels which bind metal ions.
Convenient synthesis of cyclopenta[c,d]pyrene and 3,4‐dihydrocyclopenta[c,d]pyrene. The reactivity of the pyrene dianion
Authors: Tintel C. , Cornelisse J. , Lugtenburg J.
Published: September 2010

The reactivity of the pyrene dianion has been investigated. Initial attack by electrophiles on the pyrene dianion has been shown to take place exclusively at the 4(9)‐position, leading to mono‐anions (11, 15) which can be converted into 9‐substituted 1,9‐dihydropyrene derivatives (12, 16). The latter can be rearranged to give the novel 4‐substituted 4,5‐dihydropyrene derivatives (13, 17), which provide access to 4‐substituted pyrene derivatives (14, 5). Cyclopenta[c,d]pyrene (1) and 3,4‐dihydrocyclopenta[c,d]pyrene (2), two widespread environmental contaminants, have been synthesized from pyrene in four (64%) and in five steps (62%), respectively, utilizing the chemical properties of the pyrene dianion. In these easy and straightforward syntheses the thus far unknown 4,5‐dihydro‐4‐pyreneacetic acid (17) plays a major role.
Preparation of 11,14‐epoxy‐bridged and isomeric chain‐demethylated retinals. 13‐Demethyl‐11,14‐epoxy‐, 9‐demethyl‐, 13‐demethyl‐ and 9,13‐bisdemethyl‐retinals
Authors: Broek A. D. , Muradin‐Szweykowska M. , Courtin J. M. L. , Lugtenburg J.
Published: September 2010

9‐Cis‐ and all‐trans‐13‐demethyl‐11,14‐epoxyretinyl acetate were prepared via a Wittig coupling between β‐ionylidenetriphenylphosphonium bromide (1) and 5‐(acetoxymethyl)furfural. Saponification of these acetates, subsequent oxidation and HPLC separation afforded pure 9‐cis‐and all‐trans‐13‐demethyl‐11,14‐epoxyretinal. 11‐Cis‐ and all‐trans‐9‐demethyl‐, 13‐demethyl‐ and 9,13‐bisdemethyl‐retinal were prepared via the same scheme, based on the Pommer vitamin A acetate synthesis. Their photochemistry shows the same type of solvent dependence as retinal. HPLC separation of the photostationary mixtures of these retinals yielded the all‐trans, 13‐, 11‐, 9‐ and 7‐cis isomers in 98% purity.
Carbonyl and thiocarbonyl compounds XX. Reaction of hydroxybenzaldehydes with o‐phenylenediamine; newer aspects in benzimidazole synthesis
Authors: Latif N. , Mishriky N. , Assad F. M.
Published: September 2010

The nature of the products of the uncatalysed reaction of the o‐hydroxybenzaldehydes 1a‐d with o‐phenylenediamine in boiling ethanol is mainly dependent on the molar ratio of the reactants and the nature of the substituents at the phenyl ring of the aldehyde. In contrast, the m‐ and p‐hydroxy analogues 1e‐g afford exclusively the corresponding 1‐aralkyl‐2‐arylbenzimidazoles 6, regardless of these factors. However, at low temperature, the hydroxybenzaldehydes 1a‐g react with the diamine always giving monoanils (2) regardless of the hydroxy position. The monoanils of the o‐hydroxy aldehydes afford predominantly 2‐arylbenzimidazoles (4) when boiled in n‐butanol. In contrast, those of the m‐ and p‐hydroxy analogues give exclusively 1‐aralkyl‐2‐arylbenzimidazoles (6), whereas, when heated in nitrobenzene, 2‐arylbenzimidazoles (4) are readily obtained. The dianils 5a‐d, upon boiling in butanol, give a mixture of 2‐arylbenzimidazoles (4) and 1‐aralkyl‐2‐arylbenzimidazoles (6), the ratio of which is dependent on the nature of the substituents at the aldehyde. Reaction mechanisms and spectral features of the products are discussed.
Photochemical reactions of 2‐bornanethione (thiocamphor) with bis(methylthio)ethyne. Addition and intramolecular hydrogen abstraction
Authors: Brouwer A. C. , Bos H. J. T.
Published: September 2010

Irradiation of a mixture of bornanethione 7 and bis(methylthio)ethyne 2a afforded a mixture of methyl E‐ and Z‐2‐(2‐bornylidene)‐2‐(methylthio)ethanedithioate 8 and E‐1,2‐bis‐(methylthio)vinyl 2‐bornen‐2‐yl sulfide 10E. The first compounds are the products of the (2 + 2)‐photocycloaddition reaction between bornanethione 7 and acetylene 2a. The sulfide 10E is rationalised as being the product of an intramolecular H abstraction reaction of the 1,4‐biradical 12 which is also believed to be the intermediate in the (2 + 2)‐cycloaddition reaction.
Structure and reactivity of the pyrene dianion; a 13C NMR study
Authors: Tintel C. , Cornelisse J. , Lugtenburg J.
Published: September 2010

Using 13C NMR spectroscopy, the pyrene dianion has been shown to be a completely asymmetric system having the highest charge density on the carbon atom at the 4‐position. This result, which is in contrast to that obtained previously on the basis of theoretical calculations, confirms our earlier observations that the pyrene dianion reactivity towards electrophiles is highest at the 4‐position.
Chemistry of crown ethers. Part XXI. Association constants of the complexes of 18‐crown‐6 with dimethyl sulfate, dimethyl carbonate and dimethyl oxalate
Authors: van Zon A. , Onwezen Y. , Tomassen H. P. M.
Published: September 2010

The association constants (K) of the complexes of 18‐crown‐6 with dimethyl sulfate, dimethyl carbonate and dimethyl oxalate have been determined by a 1H NMR method. The K values of these complexes were found to be 0.6, 0.8 and 0.6 l/mol, respectively, which values are several orders of magnitude lower than those reported for crown ether/ammonium salt complexes.
Solutes in sulfuric acid. Part IX. Effect of para‐substitution on the ionization of the oxonium ions of phenol and anisole
Authors: Lambrechts Hans J. A. , Cerfontain Hans
Published: September 2010

The ionization of the oxonium ions of phenol, anisole, 4‐chloro‐ and 4‐methyl‐phenol and 4‐bromo‐, 4‐fluoro‐ and 4‐methyl‐anisole in concentrated aqueous sulfuric acid has been investigated using UV spectroscopy at 25°C. The sulfuric acid concentrations at half‐ionization are within the range 75.2 to 81.8% H2SO4, corresponding with pKa's between ‐5.87 and ‐6.52 based on the H0a acidity function. The substituent effects on the ionization of PhO+ H2 and PhO+ HMe are small, the Hammet ρ values being 0.5 ± 0.1 and 0.9 ± 0.1, respectively.
Empirical force field calculations XXI. The ring inversion of cis‐transoid‐cis‐1,4,4a,5,8,8a,9,9a,10,10a‐decahydroanthracene
Authors: Tavernier D. , Baas J. M. A. , van de Graa B. , Vanhee P.
Published: September 2010

The barrier to the ring inversion of the title compound has been determined using dynamic 13C NMR: ΔG≠253 = 47.9 kJ·mol−1. Empirical force field calculations show that the (half‐chair)chair(half‐chair) ground state inverts in two equi‐energetic steps via the (half‐chair)‐twist(inverted half‐chair) conformer. The calculated ΔH≠ is 46.2 kJ·mol−1 using Allinger's MM2 and 41.7 kJ·mol−1 using White and Bovill's force field.
Preparation of sulfines by alkylidenation of sulfur dioxide using α‐silyl carbanions
Authors: Porskamp P. A. T. W. , van der Leij M. , Lammerink B. H. M. , Zwanenburg B.
Published: September 2010

The synthesis of sulfines 4 from a series of active methylene compounds is described. Deprotonation, followed by silylation, gives the trimethylsilyl compounds 2. Subsequent deprotonation to α‐silyl carbanions and treatment with an excess of sulfur dioxide leads to the formation of sulfines 4, usually in good yields. The experimental conditions of this alkylidenation of sulfur dioxide, using the modified Peterson olefination, are discussed in detail. Hydrolytically sensitive sulfines can be prepared by using a dry work‐up procedure. These sulfines can also be trapped with 2,3‐dimethyl‐1,3‐butadiene to give dihydropyran S‐oxides 5. Reaction of the α‐silyl carbanions with some sulfines leads to alkenes 9, probably through the intermediacy of thiocarbonyl S‐ylides.
Synthesis of two diphosphorylated lipid a derivatives containing α‐ or β‐anomeric phosphates
Authors: van Boeckel C. A. A. , Hermans J. P. G. , Westerduin P. , Oltvoort J. J. , van der Marel G. A. , van Boom J. H.
Published: September 2010

The preparation of two diphosphorylated Lipid A analogues, which contain α‐ or β‐phosphates at the reducing end, is described (i.e. compounds 14d and 15d, respectively). The synthesis of these compounds was accomplished using: (i) two suitably protected glucosamine derivatives, i.e. the non‐reducing part 6 and the reducing part 3; (ii) an iridium catalyst to isomerize the anomeric allyl ethers quantitatively into 1‐propenyl ethers, which can then be removed to give simultaneously oxazoline functions (i.e. isomerization of 4b into 5 and of 7a into 7b); (iii) the levulinoyl* group for temporary protection of the 4‐hydroxyl group; (iv) 1‐hydroxybenzotriazole‐activated phosphorylating agents for the phosphorylation of the 4′‐hydroxyl group (i.e. phosphorylation of compound 8 to give 10a,b); (v) 2,2,2‐tribromoethyl phosphate for the phosphorylation of the reducing anomeric centre of Lipid A analogues (i.e. phosphorylation of 11a,b to afford 13a,b).

Non‐reducing part 6 and reducing part 3 were reacted together to give the disaccharide 7a, which was converted into non‐phosphorylated Lipid A precursor 8. Phosphorylation of compound 8 at its 4′‐hydroxyl function and at its reducing anomeric centre resulted in the formation of fully protected α‐phosphorylated Lipid A analogues 14a and 14b together with the fully protected β‐phosphorylated analogues 15a and 15b. Final removal of all the protecting groups from 14a,b and 15a,b gave the α‐phosphorylated Lipid A analogue 14d and the β‐phosphorylated Lipid A analogue 15d, respectively.
Synthesis of 3‐ (1 ‐alkenyloxy) ‐1,2‐propanediols, enol ethers of glycerol, by the horner‐wittig reaction
Authors: van Schaik T. A. M. , van der Gen A.
Published: September 2010

Reaction of the anion derived from phosphine oxide 4 with saturated and unsaturated aldehydes provides diastereomeric mixtures of the adducts 5. After removal of the protecting group these can be separated and, upon reaction with base, afford the pure E‐and Z‐isomers of glyceryl enol ethers 7 in good yields.
Electrical and catalytic properties of some mixed conductors with the fluorite or pyrochlore structure
Authors: van Dijk M. P. , ter Maat J. H. H. , Roelofs G. , Bosch H. , van de Velde G. M. H. , Gellings P. J. , Burggraaf A. J.
Published: September 2010

In view of their possible use as electrocatalysts the conduction properties and the catalytic activity for CO oxidation of some lanthanide titanates partly substituted with Bi, and some Nd zirconates, partly substituted with Ce, have been determined. The lanthanide ion, the substitution and the ordering in the zirconates all influence the conduction properties and the catalytic activity.
Synthesis and complex formation of a novel, flexible, biomimetic, benzimidazole‐containing, dinucleating ligand
Authors: van Rijn J. , Reedijk J.
Published: September 2010

The synthesis and complex formation with copper(II) of a new symmetric octadentate N6O2 ligand is described. The ligand 1,1,10,10‐tetrakis(1‐methylbenzimidazol‐2‐ylmethyl)‐1,10‐diaza‐4,7‐dioxadecane (megtb) is prepared by condensation of o‐phenylenediamine and [ethylene‐bis(oxyethylenenitrilo)]tetraacetic acid, followed by methylation. This ligand appears to yield dinuclear compounds with copper(II) salts with different kinds of bridging anions. Some spectroscopic and magnetic properties of these compounds, as well as the structure of a representative compound Cu2(megtb)F2(BF4)2(H2O) 2, are reported as examples
Synthesis of α‐substituted γ,δ‐unsaturated β‐oxo esters
Authors: van den Goorbergh J. A. M. , van der Gen A.
Published: September 2010

Two approaches to the synthesis of the title compounds 3 are described. The first consists of direct alkylation of the unsaturated β‐oxo esters 1 via their monoanions. The best results were obtained using the heterogeneous sodium methoxide/alumina system. Isolation of pure, mono‐α‐alkylated compounds requires chromatographic separation of the reaction products. The second approach makes use of the Horner‐ Wittig reaction. α‐Substituted phosphine oxides 4 were converted into their dianions and reacted with aldehydes and ketones to afford the mono‐α‐alkylated β‐oxo esters 3 in good yields. The requisite phosphine oxides were obtained from the corresponding γ‐bromo β‐oxo esters 10 via an Arbusov reaction with ethyl diphenylphosphinite. Finally, it was found that α,α‐dialkylated and α,αγ‐trialkylated β‐oxo esters 8 and 15 can be obtained by reaction of 1 with an excess of alkyl halide in the presence of two or four equivalents of sodium hydride, respectively.
Use of 2‐cyano‐1,1‐dimethylethyl as a protecting group in the synthesis of DNA VIA phosphite intermediates
Authors: Marugg J. E. , Dreef C. E. , van der Marel G. A. , van Boom J. H.
Published: September 2010

The phosphitylating agent 2‐cyano January ‐dimethylethoxy dichlorophosphine and its mono‐N‐morpholino derivative proved to be suitable for the synthesis of DNA in solution and on a solid support. The 2‐cyano‐l,l‐dimethylethyl for protecting P‐0 could be removed selectively under mildly basic conditions.
Convenient conversions of codeine into 6‐demethoxythebaine via bond rearrangement (Chemistry of Opium Alkaloids, Part XVIII)
Authors: Beyerman H. C. , Crabbendam P. R. , Lie T. S. , Maat L.
Published: September 2010

Two syntheses are described of (‐)‐6‐demethoxythebaine (4), both starting from the 6‐O‐mesyl**** derivative 2 of (‐)‐codeine. Treatment with sodium hydride in toluene gives (‐)‐6‐demethoxythebaine in 60% yield. The preparation via 8β‐bromo‐6,7‐didehydro‐4,5‐epoxy‐3‐methoxy‐17‐methylmorphinan (3), which is obtained from the mesyl derivative with the aid of lithium bromide, has an overall yield of 80%.
Synthesis of the mirror image of β‐D‐riboguanosine 5′‐phosphate a substrate to study chiral selection in non‐enzymatic RNA synthesis
Authors: Visser C. M. , van Westrenen J. , van Boom J. H. , van Boeckel C. A. A.
Published: September 2010

β‐L‐Riboguanosine 5′‐phosphate (5′pLG) was prepared by transglycosidation of properly protected L‐ribose and guanine derivatives followed by phosphorylation and removal of all protecting groups. Experiments indicated that 5′pDG was selected from a mixture of L and D isomers in template directed oligomerization of RNA.
Photochemical reaction of some aromatic thiones with aryl‐ and alkyl‐substituted (methylthio)acetylenes. The (2+2)‐cycloaddition products and the occurrence of the equilibrium thiete ⇋ α, β‐unsaturated thioxo compound
Authors: Brouwer A. C. , Bos H. J. T.
Published: September 2010

Upon irradiation (λ > 525 nm), xanthenethione2oand thioxanthenethione2sreact in a non‐regiospecific manner with the triple bond of the acetylenes6a(Ph‐C≡C‐SCH3) and6b[(2‐thienyl)–C≡C‐SCH3] to produce in each case the two possible (2 + 2)‐cycloaddition products, which were isolated as thietes or α,β‐unsaturated thioxo compounds. In a solution of each of these reaction products, spectroscopic results confirmed the occurrence of the equilibrium thiete ⇋ α, β‐unsaturated thioxo compound. With acetylene6c(t‐Bu‐C≡C‐SCH3), the photochemically excited thiones2oand2sgave, in each case, only the (2 + 2)‐cycloaddition product8. In solution these thietes8do not equilibrate with the corresponding α, β‐unsaturated thiones. Surprisingly, no products could be isolated or detected after irradiation of thiobenzophenone2hin the presence of acetylenes6aor6b.
A Copper(I)‐catalyzed photochemical cyclodimerization of 1, 3, 5‐hexatriene
Authors: Bos H. J. T. , Elferink V. H. M. , van der Ploeg D.
Published: September 2010

Irradiation of neat 1, 3, 5‐hexatriene with light (λ > 334 nm) in the presence of 0.2 mol% of copper(I) trifluoromethanesulfonate affords a mixture of three dimerization products in an overall yield of 80%, consisting of 86% 4‐(E‐1, 3‐butadienyl‐3‐vinyl‐1‐cyclohexene 2˜(cis 2˜/trans2˜∼ 1˜) and 14% 1Z, 3E, 7E, 9Z‐1, 3, 7, 9 ‐cyclododecatetraene 3˜.
The synthesis of α‐amino‐substituted diphenylphosphine oxides
Authors: Broekhof N. L. J. M. , van Elburg P. , van der Gen A.
Published: September 2010

Four methods with differing but overlapping specificity are described for the synthesis of α‐unsubstituted as well as α‐substituted (aminomethyl)diphenylphosphine oxides. The first method is based on the Arbusov reaction, the second on a Mannich‐type condensation of diphenylphosphine oxide [Ph2P(O)H] with aldehydes and secondary amines, the third on the addition of Ph2P(O)H to enamines and the fourth on the reaction of anions derived from α‐unsubstituted (aminomethyl)diphenylphosphine oxides with various electrophiles.
Studies on polypeptides XLI1H NMR studies of non‐covalent, semi‐synthetic ribonuclease A analogues in which histidine‐119 has been replaced by L‐homohistidine, Nτ‐methyl‐L‐histidine, Nπ‐methyl‐L‐histidine and 3‐(3‐pyrazolyl)‐L‐alanine, respectively
Authors: Serdijn J. , Bloemhoff W. , Kerling K. E. T. , Havinga E.
Published: September 2010

1H NMR titration studies carried out at 300 or 360 MHz are described for RNase 1–120, RNase 1‐118 and five non‐covalent complexes of RNase 1‐118/RNase 111‐124, having L‐histidine, L‐homohistidine, L‐Nπ‐methylhistidine, L‐τ‐methyl‐histidine and 3‐(3‐pyrazolyl‐L‐alanine, respectively, as the active‐site amino acid in position 119. The pH titrations were performed both in the absence and in the presence of a RNase A inhibitor (3′‐CMP). From least‐squares analysis of the titration data, the most probable pKa values and intrinsic chemical shifts of the histidine side‐chain in position 12 and 105 and of the amino acid residue in position 119 were obtained. On the basis of these results, the effects of replacing the amino acid residue in position 119 and of inhibitor binding are discussed.
A convenient synthesis of fecapentaene‐12 by the Horner‐Wittig reaction
Authors: de Wit P. P. , van Schaik T. A. M. , van der Gen A.
Published: September 2010

A synthesis of racemic fecapentaene‐12 and other glyceryl enol ethers has been developed based on the Horner‐Wittig reaction. Coupling of the anion of the glyceryl substituted phosphine oxide 7˜ with unsaturated aldehydes 9a˜‐c˜ provided, after treatment with base, the silyl protected glyceryl enol ethers 11a˜‐c˜. The silyl groups were easily removed and mixtures of E and Z isomers of glyceryl enol ethers 12a˜‐c˜ were obtained. The isomers could be separated upon washing with ether/hexane.
Synthesis of the glycotripeptide alanyl‐(O‐β‐D‐galactopyranosylseryl)‐alanine using (9‐fluorenylmethoxy)carbonyl and esters of 2‐(hydroxymethyl)‐9,10‐anthraquinone as temporary protecting groups
Authors: Hoogerhout P. , Guis C. P. , Erkelens C. , Bloemhoff W. , Kerling K. E. T. , van Boom J. H.
Published: September 2010

The cesium salts of N‐[(9‐fluorenylmethoxy)carbonyl]‐L‐serine (Fmoc‐Ser, 1a)*** and ‐L‐threonine (Fmoc‐Thr, 1b) were treated with 2‐(bromomethyl)‐9,10‐anthraquinone (Maq‐Br), yielding Fmoc‐Ser‐OMaq (2a, 79%) and Fmoc‐Thr‐OMaq (2b, 74%). HgBr2‐catalyzed glycosylation with 2,3,4,6‐tetra‐O‐acetyl‐α‐D‐galactopyranosyl bromide gave Fmoc‐Ser(Ac4βGal)‐OMaq (3a, 89%) and Fmoc‐Thr(Ac4βGal)‐OMaq 13b, 53%). Fmoc‐Ser(Ac4βGal)‐OH (4), obtained by reaction of 1a with Na2S2O4 (88%), was condensed with H‐Ala‐OMaq using the DCC/HOBt method (83%). The Fmoc‐Ser(Ac4βGal)‐Ala‐OMaq(5), thus obtained, was Nα‐deprotected with morpholine and coupled with Fmoc‐Ala using water soluble carbodiimide in the presence of HOBt to yield Fmoc‐Ala‐Ser(Ac4βGal)‐Ala‐OMaq (6, 59%). The fully deprotected glycotripeptide (8) was obtained from 6 by successive treatment with Na2S2O4, morpholine and hydrazine hydrate (81%).

The compounds 3a, 6 and 8 were characterized using correlated 300 MHz 1H NMR spectroscopy (2D‐COSY).
Biomimetic total synthesis of steroids, IX. Stereospecific synthesis of C‐homo‐19‐norsteroids
Authors: Groen M. B. , Hindriksen B. , Zeelen F. J.
Published: September 2010

Cationic cyclization of 2‐[7‐(3‐methoxyphenyl)‐(E)‐4‐heptenyl]‐3‐methyl‐2‐cyclopentenol (1c) produced 3‐methoxy‐17‐methyl‐C‐homo‐1,3,5(10),13(17)‐gonatetraene (3c) and its 1‐methoxy isomer 2c. Epoxidation of 3c with tert‐butyl hydroperoxide in the presence of molybdenum hexacarbonyl produced the corresponding 13α, 17α‐epoxide 14 as the major product, which, in three steps, was converted into C‐homo‐1,3,5(10)‐estratriene‐3,17β‐diol (18).
1,6‐Anhydro‐2,3‐O‐(4‐methoxybenzylidene)‐β‐D‐mannopyranose: A useful synthon for the preparation of valuable disaccharides
Authors: Kloosterman M. , de Nijs M. P. , van Boom J. H.
Published: September 2010

Substitution of the 2‐O‐triflyl function in 4‐O‐acetyl‐1,6‐anhydro‐3‐O‐anisoyl‐β‐D‐mannopyranose with the Cs‐salt of levulinic or benzoic acid affords 4‐O‐acetyl‐1, 6‐anhydro‐3‐O‐anisoyl‐2‐O‐levulinoyl(benzoyl)‐β‐D‐glucopyranoses. Coupling of 1,6‐anhydro‐2,3‐O‐(4‐methoxybenzylidene)‐β‐D‐mannopyranose with β‐D‐galactose pentaacetate in the presence of trimethylsilyl triflate affords a β(1→4) linked disaccharide the mannose unit of which can be converted into the 3‐O‐anisoyl‐2‐O‐levulinoyl‐(benzoyl) protected glucose moiety.
Investigations into the total synthesis of momilactones. Stereoselective preparation of (±)‐4,4‐dinor‐9βH‐pimara‐7,19‐diene
Authors: Sicherer‐Roetman Annemarie , Jansen Ben J. M. , de Groot Aede
Published: September 2010

The stereoselective synthesis of (±)‐4,4‐dinor‐9βH‐pimara‐7,19‐diene, 6, is described. This compound represents the B,C‐ring system of the momilactones, fungitoxic diterpenes having a 9βH‐pimarane skeleton. The trans‐syn‐cis tricyclic system was formed via a Diels‐Alder reaction of formyl enone 9 with 2‐(tert‐butyldimethylsilyloxy)‐3‐methyl‐1,3‐butadiene. The resulting regiospecific silyl enol ether was deformylated and stereoselectively reduced to alcohol 26. This alcohol was dehydrated to alkene 22 and acylated to acetate 23, respectively. Alkylation of 22 gave the α‐dithiolanyl compound 27. Alkylation of 23 gave the β‐dithiolanyl compound 35. Compound 27, containing an α‐oriented dithiolanyl group, could be converted into model compound 6, which possesses a β‐oriented vinyl substituent as a result of an equilibrium during the Wittig reaction. Compound 35 was converted into model compound 6 in a straightforward series of transformations.
Electrochemistry of the 9‐phenyl‐10‐methyl‐acridan/acridinium redox system; a high‐potential NADH/NAD+ analogue
Authors: Koper N. W. , Jonker S. A. , Verhoeven J. W. , van Dijk C.
Published: September 2010

Cyclic voltammetry and preparative controlled potential electrolysis show that the 9‐phenyl‐10‐methyl‐acridinium/acridan (AcPh+/AcPhH) redox couple can be cycled electrochemically between the oxidized (AcPh+) and reduced states (AcPhH) without any apparent side‐reaction. The 9‐phenyl‐10‐methyl‐acridanyl radical (AcPh•) was identified as a first intermediate in the electrochemical reduction of AcPh+ by cyclic voltammetry as well as by electronic absorption and ESR spectroscopy. In contrast to other acridanyl and related dihydropyridyl radicals, AcPh• shows no tendency to undergo dimerization. In aprotic media, AcPh• is shown to undergo a second reversible one‐electron reduction to yield AcPh−, which is, even in these media readily protonated to give AcPhH. The stability of these intermediates seems to be the major factor responsible for the clean electrochemical interconversion of the AcPh+/AcPhH redox couple. The implementation of this redox couple as part of photo‐electrochemical energy conversion systems is discussed.
Potential‐controlled catalytic hydrogenation. Effect of palladium catalyst potential on the selectivity of hydrogenation of polyunsaturated fatty acid esters
Authors: Fröling A. , Hornung F. , de Jongh R. O.
Published: September 2010

Hydrogenation of methyl linoleate on palladium catalysts in solution with tetraalkylammonium perchlorate as electrolyte, leads mainly to the saturated product methyl stearate. At negative potentials of the catalyst electrode controlled at about − 1 Volt versus a saturated calomel electrode (SCE) with negligible current passage, the monoenic intermediate is the end product, with the double bond found mainly in the Z configuration at the starting 9‐ and 12‐positions. As expected it was found that methyl oleate was not hydrogenated by the catalyst held at − 1.1 Volt, while smooth hydrogenation occurs under identical conditions when the catalyst potential is not controlled. Methyl linolenate leads mainly to dienoic esters at − 1.8 V catalyst potential. The effect was applied on a synthetic scale in the hydrogenation of soya bean oil with palladium catalysts, resulting in a considerable increase of selectivity at negative catalyst potentials.
Analysis of multinuclear lanthanide induced shifts. 3. The structure of 1:3 lanthanide (III)‐glycolate complexes in aqueous solution
Authors: Nieuwenhuizen M. S. , Peters J. A. , Kieboom A. P. G. , Raber D. J.
Published: September 2010

Lanthanide induced shifts for the 17O, 13C and 1H nuclei of an aqueous solution of glycolate show that the Ln(glycolate)3(D2O)3 complex contains 9 coordinating oxygens situated on a distorted tricapped trigonal prism. The three capping positions are occupied by carboxylate oxygens, the prismatic triangles by either D2O or α‐OH.
Pentacoordinated phosphorus as the internucleoside linkage. Synthesis and 31P NMR study of the pseudorotational dynamics
Authors: Koole Leo H. , Moody Harold M. , Buck Herik M.
Published: September 2010

The synthesis of the first dinucleotide with a pentacoordinated phosphorus as the internucleoside linkage is described. 31P‐NMR measurements revealed that the phosphorus pseudorotation proceeds with rapid stereomutation.
Propellanes. Part LXXXIV. Reduction of [20.3.3]propellane‐24,27‐dione: The three isomeric [20.3.3]propellane‐24,27‐diols
Authors: Ashkenazi Pnina , Weinberg Olga , Zlota Andrei , Ginsburg David
Published: September 2010

Reduction of [20.3.3]propellane‐24,27‐dione afforded only two of the three expected diols.
I. Photochemical nitration of methoxybenzenes from charge‐transfer complexes with tetranitromethane
Authors: Sankararaman S. , Kochi J. K.
Published: September 2010

The direct irradiation of the charge‐transfer (CT) absorption band of the 1/1 electron donor‐acceptor complexes of dimethoxybenzenes with tetranitromethane leads to aromatic nitration with a high quantum yield. The analogous methoxytoluenes under the same photochemical conditions are converted in equally high yields to products of aromatic trinitromethylation. This dichotomy with different methoxybenzenes (ArH) is discussed within the context of the common reactive intermediates derived from the CT excitation of the complex. The subsequent interactions of the geminate fragments, i.e., \documentclass{article}\usepackage{amsmath}\pagestyle{empty}\begin{document}$[{\rm ArH}^{\underset{{{\scriptscriptstyle\cdot}}}{+}}, {\rm C}({\rm NO}_2)_3 ^ -,\, {\rm \dot NO}_2] $ \end{document} by radical and ion‐pair annihilation represent a unifying mechanism for the CT photochemistry leading to aromatic nitration and trinitromethylation.
Solvent polarity and solvation effects in highly aqueous mixed solvents. Application of the Dimroth‐Reichardt ET(30) parameter
Authors: Haak Jan R. , Engberts Jan B. F. N.
Published: September 2010

The Dimroth‐Reichardt solvent parameter ET(30) and its temperature dependence (25‐50°C) have been measured in water‐rich mixtures of water with acetonitrile (MeCN), 1,4‐dioxane (1,4‐D), dimethyl sulfoxide (DMSO), tert‐butanol (TBA) and 2‐n‐butoxyethanol (2‐BE). Thermodynamically nonideal behavior of the solutions is indicative for preferential solvation of the probe molecule by all organic cosolvents used. However, the effects are most pronounced for TBA and 2‐BE. This leads to ambiguities in the use of the ET(30) value as an indicator of “solvent polarity” for these aqueous binary mixtures. The temperature dependence of ET(30) in TBA‐H2O and 2‐BE‐H2O above the critical hydrophobic interaction concentration is interpreted in terms of binding of the probe to small, temperature‐sensitive aggregates of the cosolvent.
Synthesis and 119Sn NMR of η1‐O‐coordinated sulphine‐dimethyltin dichloride complexes and thermal CS and SO bond cleavage reactions: X‐Ray structure (130 K) of Me2SnCl2[η‐O‐(Me(Ph)NC(Ph)SO)]
Authors: Jans Robert J. F. , van Koten Gerard , Andréa Ronald R. , Vrieze Kees , Spek Anthony L. , Kojić‐Prodić Biserka , de Boer Jan L.
Published: September 2010

Aminosulphines (R1R2N)(R3)CSO coordinate via the oxygen atom to dimethyltin dichloride. This η1‐O coordination was established by the X‐ray structure of Me2SnCl2[η1‐O‐(Me(Ph)NC(Ph)SO)] which consists of monomers connected to dimers with unequal Sn‐Cl bridges of 2.544(1) and 3.307(1) Å. The tin centres have a distorted octahedral arrangement. The Sn‐O distance is 2.269(3) Å and the Sn‐O‐S angle is 129.1(2)°.

Theoretical calculations showed that the negative charge on the sulphine oxygen atom is enhanced by conjugation of the πCS bond with the amino lone pair of the NR1R2 group. Of the other sulphines tested, only 9‐fluorenethione S‐oxide was found to coordinate to Me2SnCl2, likewise in the η1‐O coordination mode. The η1‐O coordination to tin destabilizes the sulphine fragment as was shown by the stoichiometric decomposition of the sulphine into the corresponding ketones and thioketones. A possible route for the decomposition process is proposed involving the formation of an oxathiiran intermediate.
Synthesis of the optical antipodes of 4‐alkyl‐γ‐lactones
Authors: Thijs Lambertus , Waanders Peter P. , Stokkingreef Edwin H. M. , Zwanenburg Binne
Published: September 2010

Optical antipodes of 4‐alkyl‐γ‐lactones 3 have been prepared by photochemical rearrangement of optically active α,β‐epoxy diazomethyl ketones 1 in ethanol to give 4‐hydroxy‐alkenoates 2, followed by reduction of the alkene bond and subsequent lactonization. The required epoxy diazomethyl ketones 1 were obtained via the following sequence of reactions: alkylation of 2‐propyn‐l‐ol, subsequent reduction to the alkenols 6, Sharpless epoxidation to 2,3‐epoxy alcohols 7, oxidation to glycidic esters 8 and finally conversion to diazo ketones 1. The enantiomeric purities range from 84 to 100%.
Resonant tunnelling as a possible source of catalysis by energy‐matched enzymes
Authors: Verhoeven J. W. , Koomen G. J. , van der Kerk S. M.
Published: September 2010

It is proposed that in certain enzymes transfer of hydrogen nuclei occurs by tunnelling in a symmetrical double minimum potential.
Reactions of enamines of cyclodecanone and cyclododecanone with dimethyl acetylenedicarboxylate in apolar and in polar solvents
Authors: Vos G. J. M. , Benders P. H. , Egberink R. J. M. , Reinhoudt D. N. , Harkema S. , van Hummel G. J. , van der Weerdt A. J. A.
Published: September 2010

Enamines of cyclodecanone and cyclododecanone (1a‐d) react with dimethyl acetylenedicarboxylate (DMAD) in an apolar solvent via (2 + 2) cycloaddition and conrotatory opening of the cyclobutene ring in 3 to give the cis,trans‐cycloalkadienes 5a‐d in yields of 44–85%. The compounds 5 do not undergo further thermal or photochemical transformation of the cis,trans moiety. In methanol, the enamines react with DMAD to give bicyclo[7.2.1]dodecene (8a) or bicyclo[9.2.1]tetradecene (8b and 8c) derivatives. These reactions take place via intramolecular nucleophilic addition of the enamine moiety to the α‐methoxycarbonyl group in 10, which is formed from the intermediate Michael adduct 9. The structure of 8b was determined by single‐crystal X‐ray analysis.
Some reactions of an o‐quinone monoimide with derivatives of furan and styrene
Authors: Heine Harold W. , Williams Elizabeth A.
Published: September 2010

Diels‐Alder‐type cycloaddition reactions occur across the heterodiene system of the o‐quinone monoimide 1 when 1 is treated with the furans visnagin and 8‐methoxypsoralen. Derivatives of a new heterocyclic system are formed. Similar cycloadditions take place between the heterodiene moiety of 1 and the olefinic linkages present in 7‐methoxy‐2,4‐dimethyl‐3‐chromene (precocene I) and indene. In the former case another ring system previously uncharacterized was produced. Precocene I also reacted with o‐chloranil and an o‐quinone diimide to yield a benzopyrano[3,4‐b] [1,4]benzodioxin and a benzopyrano[3,4‐b]quinoxaline respectively.
Characteristic odoriferous compounds of brown algae: Syntheses of possible oxidation products of (6Z, 9Z, 12Z, 15Z)‐1,6,9,12,15‐heneicosapentaene and (6Z, 9Z, 12Z, 15Z, 18Z)‐1,6,9,12,15,18‐heneicosahexaene
Authors: Broekhof Nico L. J. M. , Witteveen Jan G. , van der Weerdt Anton J. A.
Published: September 2010

The unsaturated aldehydes (3Z, 6Z)‐3,6,11‐dodecatrienal (9), (2E, 4Z, 7Z)‐2,4,7,12‐tridecatetraenal (10) and (3Z, 6Z, 9Z)‐3,6,9,14‐pentadecatetraenal (11) are expected to be products of the air oxidation of heneicosapentaene 1 and heneicosahexaene 2.

The first attempts to synthesize aldehydes 9 and 11 (which failed) were based upon repeated Horner‐Wittig reactions with phosphine oxide 12. In a second attempt, acetylene chemistry was applied to prepare aldehydes 9, 10 and 11. Their olfactive properties are described.
Thermolysis of vinyl chloride in nitrogen; rates and products between 601‐681°C
Authors: Manion Jeffrey A. , Louw Robert
Published: September 2010

In a 10‐15‐fold excess of nitrogen, at normal pressure and with τ ca. 3 s, decomposition of vinyl chloride (VC) sets in at about 550°C. At 680°C about 35% decomposition takes place. Major products in this region are HCl, acetylene, 2‐chlorobutadiene and vinylacetylene (1‐buten‐3‐yne). At higher temperatures formation of tar and soot becomes increasingly important. A reaction mechanism in accord with the experimental facts is proposed and analyzed via thermo‐chemical kinetics. Free‐radical chain processes play a major part, with Cl· atoms as important carriers. H abstraction from VC by Cl· leads to ·CH = CHCl and CH2=CCl radicals, respectively. Their relative rate of formation on a per‐H basis is ca. 1/5 around 620°C. The former lose Cl· to give acetylene. The latter add to VC which leads to 2‐chlorobutadiene irrespective of the site of addition (Scheme 1). Various routes to vinylacetylene are discussed. The formation of other (minor) products such as ethylene and methyl chloride is also rationalized. Added HCl is seen to increase the acetylene/2‐chlorobutadiene product ratio with little effect on the rate of conversion of VC. This is due to reversal of the reaction leading to CH2=CCl radicals, through H‐atom transfer from HCl.