bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reactions d'insertion du phénylphosphinidène dans diverses liaisons germanium‐hétéroélément
Authors: Escudié J. , Couret C. , Satgé J. 
Published: September 2010

AbstractPhenylphosphinidene inserts into Ge‐Y bonds (Y = H, C, N, O, P) with formation of germylphosphines with a magnified image structure. However some adducts (Y = N, O, P) undergo a thermal redistribution reaction giving particularly bis(trialkylgermyl)phosphines. Insertion reactions of phenylphosphinidene into Si‐P or Ge‐P bonds of 2‐sila or 2‐germaphospholanes lead to a new class of cyclic metalla‐IVb‐diphosphines, the 3‐sila‐ or 3‐germa‐1,2‐diphosphorinanes.
Synthesis of (E,E)‐1,5‐cyclodienes. Part II
Authors: Reijnders Peter J. M. , Fransen Harrie R. , Buck Henk M. 
Published: September 2010

AbstractThe synthesis of (E,E)‐1,5‐cyclodienes is described. The preparation of these ring systems is accomplished by intramolecular coupling of (E,E)‐3,3′‐polymethylenebis(allyl bromides), with bis(1,5‐cyclooctadiene)nickel(0). In this way the fourteen, sixteen and eighteen ring can be prepared in good yield. Synthesis of the twelve ring in this manner fails and gives only cyclodimers and acyclic products.Synthesis of (E,E)‐1,5‐cyclododecadiene is accomplished by reduction of (E,E,E)‐1,5,9‐cyclododecatriene.
Synthesis of complementary DNA fragments via phosphotriester intermediates
Authors: de Rooij J. F. M. , Wille‐Hazeleger G. , van Deursen P. H. , Serdijn J. , van Boom J. H. 
Published: September 2010

AbstractThe preparation of the complementary oligodeoxyribonucleotides Ia,b and II via a modified phosphotriester method is described. The synthesis of these compounds was accomplished by using: (a) the levulinyl group for temporary and persistent blocking of the 5′‐hydroxyl; (b) the monofunctional phosphorylating agent 2,2,2‐trichloroethyl 2‐chlorophenyl phosphorochloridate (3) to introduce the phosphate moiety at the 3′‐position; (c) the benzoyl group to protect the terminal 3′‐hydroxyl; (d) acyl groups for the protection of the exocyclic amino functions of the bases; and (e) 1‐(2,4,6‐triisopropylbenzenesulphonyl)‐3‐nitro‐1,2,4‐triazole (TPS‐NT, 11c) as activating agent in the formation of phosphotriester linkages. Final removal of all protecting groups was performed by fluoride ion treatment followed by aqueous ammonia. The oligonucleotides Ia,b and II were, after purification, isolated in good yields and, as followed from HPLC analysis, in high purity.
The use of trifluoroacetic acid in the reverse‐phase liquid chromatography of peptides including secretin
Authors: Voskamp D. , Olieman C. , Beyerman H. C. 
Published: September 2010

AbstractThe reverse‐phase high‐performance liquid chromatography of underivatized peptides has been studied. The addition of trifluoroacetic acid — lipophilic ion‐pairing reagent — to the mobile phase gave excellent conditions for the analytical and preparative separation on octadecylsilyl‐silica of peptides varying in size from a 2‐peptide to a 32‐peptide (human calcitonin) inclusive.The gastrointestinal 27‐peptide hormone secretin could thus be purified on a preparative scale and intramolecular rearrangements in hexapeptide fragments of secretin could be monitored in this way.
Synthesis of porcine motilin via its sulfoxides
Authors: Izeboud E. , Beyerman H. C. 
Published: September 2010

AbstractThe protected segments corresponding to sequences 1‐8 and 9‐22 proposed for porcine motilin were synthesized mainly by the repetitive excess mixed anhydride (REMA) method. Mixed anhydride coupling of the segments gave protected motilin sulfoxide (Scheme). Deprotection with liquid hydrogen fluoride yielded the crude motilin sulfoxides which, after purification by HPLC on a semi‐preparative scale, were quantitatively reduced by iodide in aqueous trifluoroacetic acid.According to Dr. Zen Itoh, Japan, the minimum dose of our REMA‐synthesized motilin required to induce interdigestive migrating contractions (IMC) in dogs was 0.03 μg/kg.h, which indicates a potency of about ten times the standard synthetic preparation used in the assay. In a comparison with natural porcine motilin by Dr. Pierre Poitras, U.S.A., REMA‐motilin showed at least 100% immunological cross‐reactivity.
Direct proof for the occurrence of anions in the base‐induced 1,4‐elimination of alcohol from 1,4‐dialkoxy‐2‐butynes
Authors: van Rijn P. E. , Everhardus R. H. , Brandsma L. 
Published: September 2010

Abstract1,4‐Elimination of alcohols from ether of the type RO‐CH2 ‐C≡C‐CH2‐OR by treating these compounds with alkali amide, appears to be not a concerted process, but to proceed via short‐lived anions. These anions can be intercepted by ethyl bromide, present during the reaction.
Electrosynthesis of cyclopropanone adducts
Authors: van Tilborg W. J. M. , Plomp R. , de Ruiter R. , Smit C. J. 
Published: September 2010

AbstractElectroreduction of α,α′‐dihalo ketones to cyclopropanones (isolated as the hemiacetals or hemiacylals) is accomplished with good yields only with highly alkylated α,α′‐dihalo ketones. Attempts to prepare little substituted or unsubstituted cyclopropanone (derivatives) by electroreduction of α,α′‐dihalo ketones in which the carbonyl group is protected as an acylal or aminal resulted in the isolation of the desired compounds in low yields. The cyclisation reaction cannot compete successfully with side‐reactions. With acetals as the protecting group, the reductive cyclisation proceeds smoothly. Contrary to the acetals, the cyclopropanone acylals are excellent precursors for cyclopropanone.
Kinetic studies on the nucleation and growth of silicon via chemical vapour deposition
Authors: Bloem J. , Claassen W. A. Y. 
Published: September 2010

AbstractChemical vapour deposition (CVD) of silicon on various substrates is a well‐known technique in semiconductor technology.An experimental study has been made of the nucleation of silicon on SiO2, and Si3N4, substrates together with a search for rate‐limiting steps in the growth of silicon from silane (SiH4) and chlorosilanes.Analysis of the experimental data shows that the nucleation depends on the concentration of silicon adatoms on the surface, (Si*). After formation of stable nuclei and coalescence of the growing domains, further growth of silicon on silicon proceeds.For the growth of silicon via silane the rate‐limiting reaction could not be indicated exactly; addition of some HCl results in a rapid change of the surface species into SiCl2*, indicating that the rate‐limiting step has to be found at the end of the chain of surface reactions. This conclusion is confirmed by experiments with an input of SiH2Cl2, in which case the SiCl2* surface species predominates. Reduction to silicon is then found to be the rate‐limiting reaction. The reduction or desorption of chlorine probably takes place at specific sites on the surface, such as atomic surface steps where an adsorbed SiCl2, molecule can form a second silicon‐silicon bond.The adsorption of monoatomic hydrogen and chlorine on the silicon surface has been analysed and the conclusion is drawn that these surface species are not present in a sufficient concentration to turn the initial adsorption or the surface diffusion of silicon‐containing compounds into rate‐limiting reactions.
Enamine reactivity of 3‐(l‐pyrrolidinyl)heteroaromatics: Reactions with ketenes and nitro‐olefines
Authors: Mutreja H. C. , Reinhoudt D. N. 
Published: September 2010

AbstractKetenes react with 1‐pyrrolidinyl‐substituted heteroaromatics 3‐5 to give 2‐acyl derivatives 10, 13, 16‐18 and 20 and, in some cases 2: 1 reaction products 11 and 12. The latter products can be attributed to reaction of 1,4‐dipolar intermediates with a second molecule of ketene. With β‐nitro‐styrene, compounds 4b and 5 give only the corresponding 2‐alkyl‐substituted products 21 and 22, respectively. These reactions further demonstrate the “enamine‐like” character of 3‐(1 ‐pyrrolidinyl)‐substituted heteroaromatics 3‐5.
An approach to 11β‐isopropoxymethyl steroids
Authors: Loozen H. J. J. , de Winter M. S. 
Published: September 2010

AbstractA route for the preparation of 11β‐isopropoxymethyl derivatives of steroids is exemplified by the preparation of (11β, 17α)‐17‐hydroxy‐11‐(isopropoxymethyl)‐19‐norpregn‐4‐en‐20‐yn‐3‐one (1). To this end (11β)‐11‐(hydroxymethyl)‐3‐methoxyestra‐1,3,5( 10)‐trien‐17‐one cyclic ethylene acetal (2) was converted into its 11β‐(2‐hydroxyethoxy)methyl derivative 5. Oxidation of 5 to the corresponding 11β‐(carboxymethoxy)methyl derivative 7, followed by methylation and subsequent reduction gave (11β)‐3‐methoxy‐11‐[(1‐methylethoxy)methyl]estra‐,3,5(10)‐trien‐17‐one cyclic ethylene acetal (13). Birch reduction and ethinylation provided 1.
Zinc(II)‐promoted reduction of ketones by 1‐methyl‐1,4‐dihydropyridines
Authors: de Koning A. J. , Alberts‐Jansen H. J. , Boersma J. , van der Kerk G. J. M. 
Published: September 2010

AbstractZinc(II) promotes the reduction of unactivated ketones and aldehydes by (methyl‐substituted) 1‐methyl‐1,4‐dihydropyridines. Coordination of the dihydropyridines to the metal, which occurs via their annular nitrogen atoms, is essential for hydrogen‐transfer. The reductions proceed best in apolar non‐aromatic solvents, which are unable to compete with the carbonyl group of the substrate for a coordination site at the metal. Virtually no hydrogen‐transfer takes place in the absence of Zn(II) salts or when zinc coordination complexes are used in which the metal is coordinatively saturated.The results of this study are discussed in terms of a possible relationship with the role of zinc in alcohol dehydrogenases and metal‐catalyzed reductions in biomimetic systems.
Reductive elimination and skeletal rearrangement of β‐hydroxy selenide derivatives of bicyclo[4.2.l]nonatriene in a super acid medium
Authors: Gillissen Huub M. J. , Schipper Pieter , Buck Henk M. 
Published: September 2010

AbstractIn sulfur dioxide the β‐hydroxy selenides 1 and 2 produce rearranged selenides 6 and 7 upon addition of fluorosulfonic acid. Reductive elimination and subsequent attack of the selenenyl electrophile on the etheno bridge cause migration of the butadiene moiety.
Salt‐induced conversions of P(V) into P(IV) in solvents of different polarity. A tentative model for the initiation of conformational changes in DNA via the P(IV) residues
Authors: Castelijns Marianne M. C. F. , van Aken Dirk , Schipper Pieter , van Lier Johan J. C. , Buck Henk M. 
Published: September 2010

AbstractEvidence is presented for the involvement of pentaco‐ordinated phosphorus intermediates in the rate‐determining step of the de‐alkylation reactions of some phosphates and phosphonates with LiCl and LiBr. Such involvement is suggested to lead to the zwitterionic pentaco‐ordinated phosphorus complexes 5a and 5b, respectively when compounds 2a and 2b are treated with LiCl and LiBr. The existence of these complexes shows unambiguously the possibility of inducing (slight) conformational changes of phosphorus in the presence of cations and anions (or nucleophilic solvents). This approach may also be useful for the description of conformational changes in phosphate residues in DNA, thus leading to different conformations of DNA.
Complexes of nickel(II) and copper(II) halides, nitrates and thiocyanate with racemic 1‐amino‐2‐propanol as a ligand
Authors: Nieuwpoort G. , Groeneveld W. L. 
Published: September 2010

AbstractThe preparation of complexes containing Ni(II) and Cu(II) as metal ions, racemic 1‐amino‐2‐propanol as ligand together with halides, nitrate and thiocyanate as anions, is described. Infrared and ligand field spectra have been used to obtain information about the coordination of the ligand. X‐Ray powder diffractograms of the complexes have been recorded. Conclusions about the structure of the complexes are drawn.
A study of lanthanide(III) (hydroxy)carboxylate complexes in aqueous medium using lanthanide induced oxygen‐17 NMR shifts
Authors: Vijverberg C. A. M. , Peters J. A. , Kieboom A. P. G. , van Bekkum H. 
Published: September 2010

AbstractThe complexation of dysprosium(III), as the model cation for calcium(II), with a series of (hydroxy)carboxylates in aqueous medium, has been studied by 17O NMR spectroscopy. Acetate, 3‐hydroxybutyrate, glycolate, lactate, malonate, malate and citrate show fast ligand exchange on the 17O NMR time scale at 73°. The Dy(III)‐induced 17O shifts of both the ligand and the water, which are mainly due to contact interaction, provide valuable information on the complexation sites of the ligands as well as on the number of coordinated waters in the complexes. The results point to a rather constant 17O contact shift upon the formation of Dy(III)‐O bonds.On the other hand, oxydiacetate (ODA), (carboxymethoxy)succinate (CMOS) and nitrilotriacetate (NTA) show slow ligand exchange on the 17O NMR time scale at 73°. In these cases the Dy(III)‐induced shift of the 17O water resonance provides information on the stoichiometry of the complexes, i.e. the number of coordinated waters and the number of ligands.
A convenient synthesis of 1,3‐dithioles, 1,3‐thiaselenoles and 1,3‐thiatelluroles
Authors: Sukhai R. S. , Verboom W. , Meijer J. , Schoufs M. J. M. , Brandsma L. 
Published: September 2010

AbstractReaction of 1‐(chloromethylthio)‐1‐alkynes (RCCSCH2Cl, R  alkyl or phenyl) with an alkali metal sulfide, selenide or telluride gives 4‐substituted 1,3‐dithioles together with the corresponding 1,3‐thiaselenoles and 1,3‐thiatelluroles in good yields. The compounds RCCSCH2Cl can be obtained either from lithium alkynethiolates (RCCSLi) and BrCH2Cl or from alkynyllithium (RCCLi) and chloromethyl thiocyanates (ClCH2SCN).
Studies on polypeptides XXXIV. Replacement of histidine‐2 in Luliberin (LH‐RH) by L‐homohistidine
Authors: Raap J. , Kerling K. E. T. 
Published: September 2010

Abstract[Homohistidine2]LH‐RH has been synthesized by the solid phase method. NMR and CD spectra at two pH values have been measured. The remarkably low in vitro potency of the component, relative to LH‐RH, is discussed in terms of conformational differences.
Synthesis and melanotropic activity of γ‐melanotropin
Authors: Bijl W. A. A. J. , van Nispen J. W. , Greven H. M. 
Published: September 2010

Abstractγ‐MSH, a third melanotropic sequence in the N‐terminal cryptic portion of the ACTH/β‐LPH precursor molecule pro‐opiocortin, was synthesized by the fragment condensation approach. The dodecapeptide H‐Tyr‐Val‐Met‐Gly‐His‐Phe‐Arg‐Trp‐Asp‐Arg‐Phe‐Gly‐OH was tested for melanocyte‐stimulating activity on the skin of the lizard Anolis Carolinensis and was found to possess only 2.5 × 10−4 of the activity of α‐MSH.
Cycloaddition reactions of cyclooctyne with 9,10‐phenanthrenequinone and 3,5‐di‐tert‐butyl‐o‐benzoquinone
Authors: Verboom W. , Bos H. J. T. 
Published: September 2010

AbstractTreatment of a solution of 9,10‐phenanthrenequinone 4 and cyclooctyne 2 in chloroform with boron trifluoride‐ether affords the quinoid α,β‐unsaturated ketone 5 with loss of carbon monoxide. Reaction of 3,5‐di‐tert‐butyl‐o‐benzoquinone 9 with cyclooctyne 2 gives rise to formation of the Diels‐Alder adduct 10 and a bridged cycloheptadienone derivative 11; under the influence of boron trifluoride‐ether, however, the reaction leads, in addition to 11, to formation of the isomeric cycloheptadienone derivative 12, while the Diels‐Alder adduct 10 is converted into the cycloheptadienone derivative 11.
Activity and enantioselectivity in the hydrolysis of substituted phenyl esters catalysed by imidazole‐containing poly(iminomethylenes)
Authors: van der Eijk J. M. , Nolte R. J. M. , Richters V. E. M. , Drenth W. 
Published: September 2010

AbstractThe hydrolysis of achiral and chiral esters by optically active poly(iminomethylenes), [R‐NC<]n, which contain imidazole groups in their side chains R, has been studied. The polymers include poly(L‐ and D‐carbylalanyl‐L‐histidine), 2d and 2e, poly(D‐carbylalanyl‐L‐histidinol), 2f, and poly(L‐carbyl‐α‐methylhistamine), 1c. The esterolytic catalytic activity of the polymers towards neutral and charged esters increases in the series 2d, 2e >> 1c < 2f. Poly(D‐carbylalanyl‐L–histidinol) shows enantioselectivity in the hydrolysis of p‐nitrophenyl esters of D‐ and L‐amino acids, kL/kD = 1.1.
Thioureido complexes of copper(I), copper(II) and copper(III). Crystal structure of the copper(I) complex [Cu[(C6H5)NC(S)N[(C2H4)2O]]]6
Authors: Willemse J. , Bosnian W. P. , Noordik J. H. , Cras J. A. 
Published: September 2010

AbstractDeprotonated N‐phenyl,N′,N′‐dialkylthiourea (PhtuR2) complexes of Cu(I) and Cu(II) have been isolated and the existence of a Cu(III) complex inferred from electrochemical measurements. The crystal structure of Cu(I)[(C6H5)NC(S)N[(C2H4)2O]] (space group Pl̄, Z = 24, a = 10.487(9), b = 28.961(8), c = 29.579(12) Å, α = 120.72(3), β = 103.69(5), γ = 83.14(4)°) revealed 4 hexameric units per unit cell. The metals form a distorted octahedron; the ligands are situated outside six of the faces of this octahedron. The copper coordination is threefold planar; a N atom is linked to one Cu and the S atoms to two Cu atoms. The Cu–Cu distances exclude strong metal‐metal interactions. ESR measurements on Cu(II)(PhtuBu2)2 suggest a planar coordination around Cu with the N atoms in trans‐position. Cyclic voltamograms and differential pulse polarograms show the one‐electron oxidation, Cu(II)(PhtuR2)2 → Cu(III)(PhtuR2)2 + + e. The Cu(III) complex is only stable on the electrochemical time scale (scan rate 100 mV s−1).
Preparation of 6‐demethoxythebaine from neopine and its Diels‐Alder reaction with ethyl acrylate (Chemistry of opium alkaloids, Part XV)
Authors: Crabbendam P. R. , Maat L. , Beyerman H. C. 
Published: September 2010

Abstract6α‐O‐Methanesulfonylneopine (3b) was converted into 6‐demethoxythebaine (4b) with the aid of potassium tert‐butoxide. Diels‐Alder reaction of 6‐demethoxythebaine with ethyl acrylate yielded mainly 4,5‐epoxy‐6,14‐endo‐etheno‐7α‐ethoxycarbonyl‐3‐methoxy‐17‐methylmorphinan (5b), an intermediate for the synthesis of potential analgesics.
The reactivity of the cyclic systems (NPCl2)3−n(NSOX)n (n = 0,1; X = Cl, Ph) towards aziridine
Authors: van der Huizen A. A. , Jekel A. P. , Rusch J. , van de Grampel J. C. 
Published: September 2010

AbstractThe aziridinolysis of (NPCl2)3 and (NPCl2)2NSOCl proceeds both via a geminal and non‐geminal pattern, whereas (NPCl2)2 NSOPh reacts almost exclusively via a geminal pathway. The presence of a P‐amino group (pyrrolidino, piperidino or morpholino) reduces the reactivity of the phosphorus centre concerned.
Mössbauer investigation of gold cluster compounds
Authors: Vollenbroek F. A. , van der Velden J. W. A. , Bour J. J. , Trooster J. M. 
Published: September 2010

AbstractThe Mössbauer spectra of Au11L7X3, [Au11 L8X2]PF6, [Au11(dppp)5](SCN)3, [Au8L8](PF6)2 and [Au9L8](PF6)3 (L = PPh3, X = SCN, Cl or CN, dppp = 1,3‐bis(diphenyl‐phosphino)propane) are presented and interpreted on the basis of three different gold sites, namely: (1) a central gold atom, (2) peripheral gold atoms coordinated to phosphines and (3) peripheral gold atoms coordinated to (pseudo)halides. The peripheral gold atoms in all the clusters behave like linearly hybridized atoms. The zero quadrupole splitting of the central gold atom reflects the almost spherical environment of this atom in the clusters, with [Au9L8]3+ being a remarkable exception.
Synthesis, structure and magnetism of di‐μ2‐fluorobis(3,5‐dimethylpyrazole)tetrakis(5‐methylpyrazole)dicopper(II) bis(tetrafluoroborate)
Authors: ten Hoedt R. W. M. , Reedijk J. , Verschoor G. C. 
Published: September 2010

AbstractThe molecular structure of the compound Cu2F2(DMPZ)2(MPZ)4(BF4)2 (DPZ = 3,5‐dimethylpyrazole; MPZ = 5‐methylpyrazole), determined by single‐crystal X‐ray analysis, is described. The compound was obtained via partial substitution of DMPZ ligands in Cu2F2‐(DMPZ)6(BF4)2.The compound crystallizes in space group P1, with a = 9.578(2) Å, b = 9.893(1) Å, c = 10.994(2) Å, α = 104.27(1)°, β = 109.04(2)°, γ = 99.12(1)° and Z = 1. Reflection data were collected using an Enraf‐Nonius CAD‐4 single‐crystal diffractometer and graphite‐monochromated Mo‐Kα radiation. The structure was solved using conventional Patterson, Fourier and least‐squares refinement techniques. The final conventional discrepancy index (R) was 4.1%, based on 4442 independent reflections.The compound is dimeric, having asymmetric fluoro bridges (CuF: 1.904(2) and 2.258(2) Å) with a CuFCu angle of 97.19(8)° and a Cu–Cu distance of 3.131(1) Å. The copper atom is in a square‐based pyramidal coordination geometry with one fluoride ion in apical position. Strong HF interactions were observed between the NH protons of the substituted pyrazole ligands and the bridging fluoride ion as well as with one or two of the fluorides of the BF4− anion. The BF4− anion is present in two different orientations having one BF bond in common, i.e. they are related by a rotation around this BF bond.Magnetic susceptibility measurements down to 2 K and EPR spectroscopy showed the existence of weak super‐exchange interactions (|J| < 0.4 cm−1). These results are discussed in relation to the available structural information.
Spectral sensitization of SnO2 electrodes with Cu(I)‐based dyes
Authors: Breddels P. A. , Berdowski P. A. M. , Blasse G. 
Published: September 2010

AbstractThe spectral sensitization of SnO2 electrodes with some Cu(I) complexes is reported. Excitation into the metal‐to‐ligand charge transfer (MLCT) states gives rise to sensitized anodic photocurrents. The positions of the maxima in the action spectra depend on the ligands.
Isolation and synthesis of 3‐(2‐butenyl)‐2,4,4‐trimethyl‐2‐cyclohexen‐1‐one. Regiospecific oxidation of 1‐(2‐butenyl)‐2,6,6,‐trimethylcyclohexene
Authors: van der Weerdt Anton J. A. , Apeldoorn Willem , Boelens Mans , Könst Wil M. B. , Heide Roel Ter 
Published: September 2010

Abstract(E)‐ and (Z)‐3‐(2‐butenyl)‐2,4,4‐trimethyl‐2‐cyclohexen‐1‐one 1 and 2 have been isolated from an absolue of Osmanthus Fragrance Lour. and a fusel oil concentrate. Structural proof for these compounds has been obtained via their synthesis from β‐ionone. The key step in this synthesis is the regio‐specific oxidation of 1‐(2‐butenyl)‐2,6,6‐trimethylcyclohexene.
Synthesis of thiazoles and imidazoles from isothiocyanates and tosylmethyl isocyanide. Base‐induced ring transformation of 5‐amino‐1,3‐thiazoles to imidazole‐5‐thiols
Authors: van Nispen Simon P. J. M. , Bregman Jacob H. , van Engen Douwe G. , van Leusen Albert M. , Saikachi Haruo , Kitagawa Tokujiro , Sasaki Hideaki 
Published: September 2010

AbstractBase‐induced cycloadditions of tosylmethyl isocyanide to a series of isothiocyanates have been investigated. Depending on the reaction conditions, thiazoles 5 and/or imidazoles 7 are obtained, with the thiazoles, in particular, being obtained with high regiospecificity. During the course of this work a high‐yield ring transformation of 5‐amino‐1,3‐thiazoles (5) to imidazole‐5‐thiols (7) was discovered, which has not been previously reported. A number of reactions of 7 are described.
Ring inversion in some fully α‐methylated cycloalkane‐1,2‐diones
Authors: Verheidt Paul L. , Kruk Cor , Cerfontain Hans 
Published: September 2010

AbstractVariable‐temperature NMR spectra of 3,5,5,5‐tetramethylcyclopentane‐1,2‐dione (1a) and its 6‐, 7‐ and 8‐membered homologues (1b‐d) showed conformational isomerization for the letter three compounds, the barrier to their ring inversion being 37.5, 38.9 and 62.7 kJ/mol, respectively.
Reduction of a 3,4‐cyclic‐substituted 2H‐1‐benzopyran‐2‐one with lithium in liquid ammonia
Authors: Driessen R. A. , Salemink C. A. 
Published: September 2010

AbstractReduction of the α,β‐unsaturated lactone system in 1‐hydroxy‐3‐pentyl‐7,8‐dihydro‐spiro[dibenzo[b,d]pyran‐9,2′‐[1,3]dioxolan]‐6(10H)‐one (3) with lithium in liquid ammonia leads to cis products.