bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electronic spectra and a theoretical study of the quinolizinium cation and the bromoquinolizinium cations
Authors: Párkányi Cyril , Sanders Georgine M. , van Dijk Marinus , Havinga E. 
Published: September 2010

AbstractThe PPP (Pariser‐Parr‐Pople) method has been used to study the quinolizinium ion (1) and the four isomeric bromoquinolizinium ions (2–5). The results have been used to interpret their electronic absorption and emission (fluorescence, phosphorescence) spectra. Also, predictions concerning the chemical reactivity of these compounds have been made and compared with the available experimental data.
Conformational equilibria of (E)‐6‐bromo‐7‐hydroxy‐3,7‐dimethyl‐2‐octene
Authors: van Dommelen M. E. , van de Ven L. J. M. , Buck H. M. , de Haan J. W. 
Published: September 2010

AbstractThe 1H NMR spectral parameters of the title compound have been determined in cyclohexane‐d12 and p‐dioxane‐d8 solutions by means of high‐frequency NMR. The results are interpreted in terms of conformational equilibria.Linear Electric Field (LEF) effects may play a major role in explaining the differences between the 13C NMR chemical shifts of the title compound and those of the model (E)2,6‐dimethyl‐2,6‐octadiene. Some preliminary calculations of the LEF‐induced shifts are presented, as well as the problems involved in the recognition of the LEF contributions to the experimental shift differences.
A convenient synthesis of 2′‐O‐acetal‐N2‐acyl derivatives of riboguanosine
Authors: Verdegaal C. H. M. , Jansse P. L. , de Rooij J. F. M. , Veeneman G. , van Boom J. H. 
Published: September 2010

AbstractThe partially protected and crystalline 2′‐O‐levulinoyl‐3′5′‐O‐(tetraisopropyldisiloxane‐1,3‐diyl)guanosine derivative (4) serves as a key intermediate for the synthesis of 2′‐O‐acetal‐N2‐acylriboguanosines 1c. Acylation of 4 with diphenylacetic anhydride gave, after hydrazinolysis of the levulinoyl group, the N2‐acyl derivative 6 in high yield. Acylation of 4 with benzoyl or biphenyl‐4‐carbonyl chloride afforded the corresponding N2‐acyl derivatives in lower yields. Acetalization of derivatives 6 with 4‐methoxy‐5,6‐dihydro‐2H‐pyran, followed by the removal of the 1,1,3,3‐tetraisopropyldisiloxane‐1,3‐diyl (TIPS) group, gave the corresponding 2′‐O‐acetal‐N2‐acylriboguanosines 1c.
Mechanism of the vapour‐phase dehydrogenation of methanol on silver
Authors: Aneke L. E. , den Ridder J. J. J. , van den Berg P. J. 
Published: September 2010

AbstractThe dehydrogenation of methanol to formaldehyde in the absence of oxygen on a silver catalyst has been studied in a pulse system. The results suggest that the reaction is initiated on the surface of the catalyst, and that the formation of formaldehyde proceeds homogeneously in the gas phase. Formaldehyde yields per pass of more than 40% were obtained at 670°C with a contact time of 0.001 sec.
Chemical synthesis of a 5′‐ and 3′/2′‐phosphorylated heptamer sequence of E. coli tRNA: pAGCCUGG(3′/2′)p via phosphotriester methods
Authors: den Hartog J. A. J. , van Boom J. H. 
Published: September 2010

AbstractThe synthesis of the 5′‐ and 3′/2′‐phosphorylated heptamer sequence pAGCCUGG(3′/2′)p, corresponding to the fragment 14–20 of E. coli tRNAfmet, is described. The assemblage of the fully protected heptamer 16 was effected via a modified phosphotriester approach which is based on the use of the monofunctional phosphorylating agent, 2,2,2‐trichloroethyl 2‐chlorophenyl phosphorochloridate (3). Thus, various suitably protected building blocks were prepared which were phosphorylated with 3 on the 3′‐hydroxyl function (e.g. compounds 4 and 5). For the introduction of the 5′‐ and 3′/2′‐phosphate functions, two terminal building blocks were synthesized; one with, inter alia, a 5′‐O‐(phenyl benzyl phosphoroamidate) function (8) and another with 2′‐O‐(diphenyl phosphate) and 3′‐O‐propionyl groups (10). The latter intermediates (i.e. compounds 4, 5, 8 and 10) were assembled to give the fully protected heptanucleotide (16). Complete deprotection of 16 by base and acid treatment gave the required heptamer.
The chemistry of small ring compounds. Part 45 Thermolysis and photolysis of l‐(alkylthio)cyclopropyl azides
Authors: Jorritsma R. , Steinberg H. , de Boer Th. J. 
Published: September 2010

Abstract1‐(Alkylthio)cyclopropyl azides ‐ readily accessible from the corresponding chlorides and bromides ‐ are smoothly decomposed at 70°C with nitrogen evolution. The main process is a ring enlargement to 2‐(alkylthio)azetines 2, accompanied by cleavage to thiocyanate and alkene. Reaction parameters for the thioazetine formation suggest a two‐step mechanism involving an intermediate cyclopropylnitrene. Ring enlargement can be averted if the alkylthio group contains a double bond. Thus, the allylthiocyclopropyl azide 8 gives a nitrene that can interact not only with the three‐membered ring but also with the double bond, leading to spirocyclic products (15 and 16 in Scheme 1). The photolysis (300 nm) of these azides gives exclusively the fragmentation products thiocyanate and olefin.
An efficient synthesis of 3‐arylpiperidines
Authors: Loozen H. J. J. , Brands F. T. L. 
Published: September 2010

AbstractAn alternative route to 3‐arylpiperidines is described, thereby circumventing traditional Michael addition of substituted phenylacetonitriles to methyl acrylate. Treatment of (3‐methoxyphenyl)acetonitrile (2) with the THP ether of 3‐bromo‐1‐propanol, followed by chromic acid oxidation and saponification provided 2‐(3‐methoxyphenyl)glutaric acid (6). Treatment of the corresponding anhydride 7 with alkyl‐ and arylalkylamines provided the imides 8a‐c. Replacement of the methoxy group by a benzyloxy group, followed by LiAlH4 reduction and a catalytic reduction provided 1, 12 and 13.
A study of the reactions of 1,3‐diynes with organo‐cuprates and ‐argentates
Authors: Kleijn H. , Tigchelaar M. , Meijer J. , Vermeer P. 
Published: September 2010

Abstract1,3‐Diynes HCCCCR′ (1, R′  H or Ph) are converted by cuprates [RCuY]M′ (R  alkyl; Y  Cl, Br or R; M′  Li, MgCl or MgBr) into a mixture of [HC(CuY)C(R)CCR′]M′ (2) and [RCHC(CuY)CCR′]M′ (3). When R is n‐alkyl, adducts2are the major products; adducts3are preferentially formed when R is a branched alkyl. Organoargentates [RAgY]MgCl (R  alkyl, Y  Br or R) convert diynes1selectively into [RCHC(AgY)CCR′]MgCl (6). The latter regiospecific reaction has been used to prepare functionally substituted enynes RCHC(E)CCR′ (7: E  Br, I, allyl, CO2H) in good yields.
Chemistry of ketene acetals IV. A simple and general method for the preparation of 4‐hydroxy‐γ‐butyrolactones and 2‐butenolides from 1,1‐dimethoxypropene and α‐acyloxy aldehydes and ketones
Authors: Aben R. W. , Hofstraat R. , Scheeren J. W. 
Published: September 2010

Abstractα‐Acyloxy aldehydes (2a,b) react with 1,1‐dimethoxypropene (1) in the presence of ZnCl2 to yield 2,2‐dimethoxy‐3‐methyloxetanes (3a,b). Stronger electron‐withdraxing acyl groups are necessary for the analogous conversion ofα‐acyloxy ketones (2c,d,e). Hydrolysis of the acyloxy group with potassium hydroxide yields the corresponding hydroxyoxetanes (4) which rearrange under neutral or weakly acidic conditions to 2,2‐dimethoxy‐3‐methyl‐4‐hydroxytetrahydrofurans (5). By mild acidic hydrolysis of 5, the corresponding γ‐butyrolactores (6) are obtained in moderate to good yields. Treatment of 6 with concentrated sulfuric acid yields 3‐methyl‐2‐(5H)‐furanones (3‐methylbutenolides, 10).
Synthesis of the self‐complementary RNA‐DNA hybrid:R(GCG)D(TATACGC)
Authors: van Boeckel C. A. A. , van der Marel G. A. , Wille G. , Westerink H. , Wang A. H. J. , Mellema J. R. , Altona C. , van Boom J. H. 
Published: September 2010

AbstractA nucleic acid fragment containing a RNA trimer and a DNA heptamer wich are linked by a 3′‐5′‐internucleotide phosphodiester bond has been synthesized by a phosphotriester approach. The sequence of the nucleosides is such that they will form a self‐complementary double‐helical fragment which may serve as a probe to get more insight into the process of discontinuous DNA replication.
Synthesis of α,β‐γ,δ‐unsaturated sulfones and sulfoxides via the Horner‐Emmons reaction
Authors: de Jong B. E. , de Koning H. , Huisman H. O. 
Published: September 2010

Abstractα,β‐γ,δ‐Unsaturated sulfones and sulfoxides have been prepared via the Horner‐Emmons reaction of α,β‐unsaturated carbonyl compounds with α‐phosphoryl sulfones and sulfoxides.
Addition of dithio esters and trithiocarbonates to 1‐(diethylamino)propyne. Formation of α, β‐unsaturated thioamides and vinylogous thioamides
Authors: Elferink V. H. M. , Visser R. G. , Bos H. J. T. 
Published: September 2010

Abstractα,β‐Unsaturated thioamides and vinylogous thioamides have been prepared by thermal addition of trithiocarbonates RS‐C(S)SR1 to 1‐(diethylamino)propyne. Aromatic dithio esters Ar‐C(S)SR only gave the α,β‐unsaturated thioamides. The dithio ester Me2CH‐C(S)SMe adds as acidic enethiol tautomer Me2CC(SH)SMe to 1‐(diethylamino)propyne. Reaction mechanisms and the stereochemistry of the adducts are discussed.
Replacement of hydrogen fluoride in solid phase peptide synthesis by methanesulfonic acid
Authors: van Nispen J. W. , Polderdijk J. P. , Janssen W. P. A. , Greven H. M. 
Published: September 2010

AbstractThe dangerous liquid HF, which in addition causes many side‐reactions, has successfully been replaced by the easy‐to‐handle organic acid methanesulfonic acid for the cleavage of small peptides from the standard Merrifield resin.
Reactions of tert‐butylsulfinyl chloride with tert‐butyl hydroperoxide and tert‐butyl hydrodisulfide in the presence of pyridine. Observation of 1H CIDNP effects
Authors: Bleeker Ido P. , Engberts Jan B. F. N. 
Published: September 2010

Abstracttert‐Butylsulfinyl chloride (1) reacts smoothly with tert‐butyl hydroperoxide (2) in the presence of pyridine to afford a variety of products including pyridinium tert‐butylsulfonate, tert‐butyl tert‐butylthiolsulfonate, tert‐butanol and tert‐butylsulfonyl chloride. The mechanistic pathway most likely involves homolytic cleavage of the initially formed tert‐butyl tert‐butyl‐peroxysulfinate (5) via a radical cage process. 1H CIDNP effects provide strong evidence in support of the radical pair mechanism. The homolytic dissociation of 5 contrasts with the preferred heterolytic cleavage of peroxysulfonates.Under similar reaction conditions, 1 reacts with tert‐butyl hydrodisulfide (3) to afford tert‐butylsulfinyl tert‐butyldisulfide (13) in a yield of 90%. As compared with 5, thermal decomposition of 13 is much slower, reflecting the higher SOS bond dissociation energy in 13, relative to the low OO bond dissociation energy in 5. At elevated temperatures, 13 yields tert‐butyl tert‐butylthiolsulfonate and di‐tert‐butyl tetrasulfide, probably via a homolytic pathway.
Synthesis and photochemical reactivity of bilirubin model compounds
Authors: de Groot J. A. , van der Steen R. , Fokkens R. , Lugtenburg J. 
Published: September 2010

AbstractThe bilirubin model compounds 1, 2 and 3 were prepared in good yield. The photochemistry of 1, 2 and 3, which all have the 4Z,15Z form, was investigated; they show a Z‐E isomerisation to the 4Z,15E and the 4E,15E isomers. Unlike the isomers of 1, those of the compounds 2 and 3, could be isolated in a pure form.
Photochemistry of chloro‐2‐vinylstilbenes
Authors: Op den Brouw P. M. , Laarhoven W. H. 
Published: September 2010

AbstractShort irradiation at 300 nm of α‐chloro‐ and β‐chloro‐2‐vinylstilbene (20 and 21) leads to a mixture of 2‐vinyltolane (35) and 2‐vinylstilbene (1) accompanied by the cis‐ and trans‐isomers of the starting compounds. Evidence is found for the occurrence of an ionic intermediate during the photolysis of 20 in methanol. At 360 nm, an additional, small amount of 1‐chloro‐endo‐ and 1‐chloro‐exo‐6‐phenylbenzobicyclo[3.1.0]hex‐2‐ene (39) is formed from 20. The elimination of hydrogen chloride also occurs during the irradiation of 2‐(2‐chlorovinyl)stilbene (23) and leads to 2‐ethynylstilbene (41). The acetylenic compounds are photocyclized into 2‐phenylnaphthalene (38). However, 2‐(1‐chlorovinyl)stilbene (22) reacts without loss of chlorine to give 1‐chloro‐exo‐5‐phenylbenzobicyclo[2.1.1]‐hex‐2‐ene (40). This exceptional reaction mode is due to a much higher rate of photocyclization resulting from less distortion in the stilbene moiety and a preference for a conformation better suited to the reaction of the 2‐(1‐chlorovinyl)stilbene molecule. It is shown that both isomers of 22 can photocyclize into 40.
Palladium(0)‐catalysed conversion of α‐acetylenic epoxides into α‐allenic alcohols. Novel route to (±)‐2,3‐octadiene‐5,7‐diyn‐1‐ol, a metabolite from fungus Cortinellus berkeleyanus
Authors: Kleijn H. , Meijer J. , Overbeek G. C. , Vermeer P. 
Published: September 2010

Abstractα‐Acetylenic epoxides,R′CCCR″CH2 (1), have been converted into α‐allenicalcohols, RR′CCCR″‐CH2OH (3), by means of a palladium(0)‐promoted reaction with R‐ZnCl (2; R: Me3Si(C≡C)n‐(n=1 or 2), H2CCH‐ or t‐BuCHCCH‐). Using this method, an improved synthesis of (±)‐2,3‐octadiene‐5,7‐diyn‐1‐ol, a metabolite from fungus Cortinellus berkeleyanus, has been developed. The method is not suited to the preparation of α‐allenic alcohols from 1 and, for example, BuZnCl because of substantial formation of reduction products, HCR′CCR″‐CH2OH. For the preparation of 3 from R = Me3SiC≡C other acetylides Me3SiC C‐M were also studied, viz. M = Li, MgCl, Cu or Cu1/2Li1/2 but only with the cuprate could a reasonable conversion of 1 be realized.
A model study of the role of the CONH2‐group in the redox Co‐enzyme NAD(P)+‐NAD(P)H
Authors: van Lier P. M. , Donkersloot M. C. A. , Koster A. S. , van Hooff H. J. G. , Buck H. M. 
Published: September 2010

AbstractA model is offered for the role of the CONH2‐group in the stereospecific incorporation of hydride at C(4) in NAD(P)+‐like compounds.
Solid‐phase synthesis of the RNA fragment: rAAGAAGAAGAAGA
Authors: van der Marel G. A. , Wille G. , van Boom J. H. 
Published: September 2010

AbstractThe synthesis of the tridecaribonucleotide AAGAAGAAGAAGA on a polystyrene solid support via a phosphotriester approach is described. The assemblage of the oligomer was performed by four repeated coupling reactions of the partially protected trimer AAGp(3′) with an immobilized dimer in the presence of the activating agent (2,4,6‐triisopropylbenzenesulfonyl)‐3‐nitro‐1,2,4‐triazole. Purification of the RNA fragment was easily achieved by Sephadex G50 column chromatography.
Reaction of 1‐alkynyl thiocyanates with nucleophilic reagents. Synthesis of 2,4‐disubstituted 1,3‐thiazoles
Authors: de Jong R. L. P. , Meijer J. , Sukhai R. S. , Brandsma L. 
Published: September 2010

AbstractReaction of 1‐alkynyl thiocyanates RC≡C‐S‐C≡N (1) with alcohols, phenol or thiols or secondary aliphatic amines in the presence of anhydrous zinc chloride or boron trifluoride diethyl etherate gives mixtures of 2,4‐disubstituted 1,3‐thiazoles (2), thiocarbonyl compounds (3) (thiono esters, dithio esters or thioamides) and 2‐alkylidene‐1,3‐dithioles (4). In all cases, the 1,3‐thiazoles can be obtained in good yields if the proper reaction conditions are applied. Interaction between 1 and lithium dialkylamides LiNR′2 gives the compounds RC≡C‐S‐NR′2 (5) (attack on sulfur). With alkoxides R′O⊖, the primary attack is on C≡N•• the intermediary alkynethiolate RC≡C‐S⊖; subsequently reacts with the alkyl cyanate R′OC≡N to afford 1‐alkynyl sulfides RC≡C‐SR′ (6).
Experimental and calculated thermodynamic data for the isomeric methylcyclohexenes and methylenecyclohexane
Authors: Peereboom M. , van de Graaf B. , Baas J. M. A. 
Published: September 2010

AbstractThe equilibria in the isomerisation of the methylcyclohexenes and methylenecyclohexane have been investigated in the temperature range of 413 to 523 K. ΔrH and ΔrS have been calculated from the experimental data for the following equilibria: methylenecyclohexane ⇄ 1‐methylcyclohexene, 3‐methylcyclohexene ⇄ 1‐methylcyclohexene and 4‐methylcyclohexene ⇄ 1‐methylcyclohexene. The resulting values for ΔrH and ΔrS are respectively: 7.3 ± 1.7, 7.6 ± 0.5, and 6.7 ± 0.4 kJ mol−1 and −15.9 ± 0.3, 1.0 ± 1.6 and 1.5 ± 1.4 J mol−1K−1. These data are compared with values calculated using molecular mechanics.
Derivatives of m‐di‐tert‐butylbenzene. Part VII. 1H Nuclear magnetic resonance spectra of some sterically crowded halogenated aromatic compounds
Authors: de Koning Adrianus Jan 
Published: September 2010

AbstractThe 1H NMR spectra of seven series of halogenated derivatives of m‐di‐tert‐butylbenzene have been analysed. The results show that the hydrogen atom between the tert‐butyl groups is screened from the magnetic influence of the halogen atoms. The results also show that the effect of a halogen atom on the chemical shift of hydrogens ortho and meta to halogen is substantially reinforced by a tert‐butyl group buttressing the halogen.
Aromatic sulfonation 85. Halogen directing and steric effects in the sulfonation of the twelve halogenotoluenes and some related compounds
Authors: Cerfontain Hans , Koeberg‐Telder Ankie , Laali Khosrow , Lambrechts Hans J. A. , de Wit Peter 
Published: September 2010

AbstractThe isomer distributions for the sulfonation of the twelve halogenotoluenes and some trisubstituted halogenomethylbenzenes, with both 98.4% H2SO4 at 25°C and sulfur trioxide in nitromethane at 0°C, have been determined and found to be very similar. The predominantly para‐directing effect of the halogen substituent dominates over that of the methyl substituent: with the 2‐halogenotoluenes, the degree of 5‐substitution decreases from ≥90% for the fluoro to 50% for the iodo compound. The 2‐ to 3‐sulfonation ratio of the 4‐halogenotoluenes strongly increases on going from fluorine (0.5) to iodine (7). The ratio of the partial rate factors for the sulfonation of a halogenobenzene ortho and meta to halogen varies from 17 ± 1 for the fluoro to 1.5 ± 0.4 for the iodo substituent.In competition to the sulfonation, 2‐ and 4‐iodotoluene undergo deiodination. The latter process is more important with the 4‐isomer and with the protic sulfonating reagent. With the aprotic reagent, the reaction proceeds by direct sulfodeiodination, whereas with the sulfuric acid reagent, it proceeds by initial protiodeiodination and subsequent sulfodeprotonation.
1H and 13C NMR spectra of mianserin and 10‐hydroxymianserin derivatives in solution. Spectral assignments and conformational conclusions
Authors: Funke Carel W. 
Published: September 2010

AbstractThe 1H and 13C spectra of mianserin, 1, reveal a perfectly chair‐formed piperazine ring having an equatorial N‐methyl group, a trans‐piperazine‐dihydroazepine ring junction and a nonplanar dihydroazepine ring. The 1H spectra of the 10‐hydroxymianserin derivatives 2 and 3 show that their dihydroazepine ring conformation is similar and that C(10) ‐ the upper bridge ‐ is twisted towards the N(5) lone pair.
Synthesis and properties of 2,2′‐pyrromethene‐5[1H]‐one analogues: The furan, thiophene, benzene, 4‐methoxybenzene, 2‐pyridine and 4‐pyridine analogues
Authors: de Groot J. A. , Jansen H. , Fokkens R. , Lugtenburg J. 
Published: September 2010

AbstractCondensation of furfural, thiophene‐2‐carboxaldehyde, benzaldehyde, 4‐methoxybenzaldehyde, pyridine‐2‐carboxaldehyde and pyridine‐4‐carboxaldehyde with 3,4‐dimethyl‐3‐pyrrolin‐2‐one leads to the Z‐2,2′‐pyrromethene‐5[1H]‐one analogues. Following irradiation with light, the E forms have been isolated and characterized. Complete thermal E→Z isomerization is observed upon heating in basic methanol. On irradiation in non hydrogen‐donating solvents the analogues 3a, 3b and 3e show very little or no photoisomerisation due to the intramolecular hydrogen bond. Condensation of these aldehydes with 1,3,4‐trimethyl‐3‐pyrrolin‐2‐one gives mixtures of the corresponding Z‐ and E‐2,2′‐pyrromethene‐5[1H]‐one analogues. The Z and E forms both isomerise thermally upon heating in basic methanol to give the same equilibrium state as is observed during the synthesis. Upon irradiation with light, the compounds similarly undergo Z‐E isomerisation.
Bond dissociation energies in 2‐methoxy‐3‐phenylpropionitrile and in bibenzyl; capto‐dative stabilization of the cyano methoxy methyl radical
Authors: Louw Robert , Bunk Jaap Joosting 
Published: September 2010

AbstractIn the temperature region of 800–900K the rate of CC bond homolysis in 2‐methoxy‐3‐phenylpropionitrile (˜1a) is 2‐3 times faster than in bibenzyl (˜2a), from which it is inferred that the “capto‐dative” stabilization of the CH(OMe)CN radical is ca. 4 kcal/mol.
Intramolecular complexation in N,N′‐bis(2‐carbamoylethyl)‐diaza‐18‐crown‐6
Authors: van Zon A. , Coleman B. , Blaauw L. P. , Torny G. J. , Frijns J. H. G. 
Published: September 2010

AbstractThe 2‐carboamoylethyl side chains in 7,16‐bis(2‐carbamoylethyl)‐1,4,10,13‐tetraoxa‐7,16‐diazacyclooctadecane are shown by NMR to be preferentially complexed as in the anti conformation ˜2.
The complexation of calcium(II) and lanthanide(III) cations with the phosphate substitute (carboxymethoxy)succinate (CMOS), as studied by magnetic resonance spectroscopy
Authors: Vijverberg C. A. M. , Peters J. A. , Bovée W. M. M. J. , Vroon H. , Kieboom A. P. G. , van Bekkum H. 
Published: September 2010

AbstractThe complexation of trisodium (carboxymethoxy)succinate (Na3CMOS) with calcium(II) and with lanthanide(III) cations has been studied using NMR spectroscopy. Structural information has been obtained from lanthanide‐induced shifts (LIS), T1 relaxation rate enhancements and vicinal 1H coupling constants. CMOS forms 1:1 and 1:2 complexes in which it mainly acts as a tetradentate ligand via the three carboxylate groups and the ether oxygen. LIS measurements on non‐racemic mixtures of Na3CMOS indicate self‐association of the Ln(III) complexes at [CMOS]0 > 0.01 M.
A model for the transfer of conformational change in the phospholipid headgroup towards the hydrophobic interior of the membrane via a PV trigonal bipyramidal intermediate
Authors: Merkelbach Ingrid I. , Buck Henk M. 
Published: September 2010

AbstractCo‐ordination change of phosphorus may be responsible for a decrease of the cross‐sectional area of the phospholipid headgroup and a reduction of the difference in effective chain length between both acyl chains of a phospholipid molecule. Both factors induce a change in the angle of tilt of the acyl chains, leading to increasing or decreasing lateral phase separation.
A migration process in some sulphur‐substituted cycloheptatrienes studied using saturation transfer NMR
Authors: Zwaard A. W. , Erkelens C. , Kloosterziel H. 
Published: September 2010

AbstractModified Forsén‐Hoffman experiments (in the FT mode) show that, in 7‐substituted cyclohepta‐1,3,5‐trienes benzenesulphonyl groups migrate in a random way, while phenylthio substituents show a specific 1,2‐migration. Activation parameters for the migration process are given for a number of compounds.
Photochemistry of dienones. Part 11. Photochemistry of the pivaloyl analogues of (E)‐α‐ and (E)‐β‐ionone
Authors: Visser Cornelis P. , van der Wel Hans , Cerfontain Hans 
Published: September 2010

AbstractThe photochemical reactions of 1b and 15b, i.e. the pivaloyl analogues of (E)‐α‐ (1a) and (E)‐β‐ionone (15a), have been examined. The replacement of the acetyl group in 1a by a pivaloyl group does not change the initial photoreactions up to the retro‐ionone stage, although beyond this stage a change is observed. The retro‐α‐ionone analogue 4b undergoes α‐cleavage, followed by decarbonylation and recombination of the resulting radicals. Irradiation of the retro‐γ‐ionone analogue 18b yields the tricyclic oxetane 19b and the decarbonylated product 22. The formation of 11 in the α‐series and of 22 in the β‐series is explained in terms of a photochemical [1,3]‐hydrogen shift in 10 and 21, respectively.