bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigations on sterols XXXIII: Synthesis of 18‐alkyl‐9β,10α‐pregnane derivatives
Authors: van Moorselaar R. , Halkes S.J. 
Published: September 2010

AbstractThe 20‐cyanohydrin of 9β,10α‐progesterone was converted into 18‐cyano‐9β,10α‐progesterone by the so‐called hypoiodite reaction. The latter compound was used as a starting material for the synthesis of several 18‐alkyl‐9β,10α‐pregnanes. Interesting biological activities were found in the 18‐methyl‐9β,10α‐pregnane series.
Investigations on sterols XXXIV: Synthesis of 18‐methyl‐9β,10α‐androstanes
Authors: Halkes S.J. , van Moorselaar R. 
Published: September 2010

AbstractChemical degradation of the side chain of 18‐methyl‐9β, 10α‐progesterone gave 18‐methyl‐9β,10α‐androst‐4‐ene‐3,17‐dione in an overall yield of 45‐50%. Starting from this compound several substituted 18‐methyl‐9β,10α‐androstanes were synthesized, for which interesting biological activities were found.
Hydrogenation of 1,3,5‐tri‐t‐butylbenzene over platinum and palladium: Synthesis of cis,cis‐ and cis,trans‐1,3,5‐tri‐t‐butylcyclohexane
Authors: van Bekkum H. , Buurmans H. M. A. , van Minnen‐Pathuis G. , Wepster B. M. 
Published: September 2010

AbstractThe liquid phase hydrogenation of 1,3,5‐tri‐t‐butylbenzene (I) over palladium, platinum and rhodium has been studied. Cis‐1,3,5‐tri‐t‐butylcyclohexene (II) is shown to be an important intermediate in the hydrogenation of I. The rates of hydrogenation of I, II, and some other alkylsubstituted benzenes and cyclohexenes over palladium and platinum have been compared.The isomeric 1,3,5‐tri‐t‐butylcyclohexanes and 1,3,5‐tri‐t‐butylcyclohexenes have been prepared. The conformation of cis, trans‐1,3,5‐tri‐t‐butylcyclohexane
C‐nitroso compounds. Part X: C‐nitroso compounds as hydrogen bond acceptors
Authors: Engberts J. B. F. N. , Wajer Th. A. J. W. , Kruk C. , de Boer Th. J. 
Published: September 2010

AbstractIntermolecular hydrogen bonding between phenol and a series of monomeric and trans‐dimeric C‐nitroso compounds has been studied by IR and PMR spectroscopy.The rather small OH stretching frequency shifts Δv for monomeric C‐nitroso compounds indicate a weak “ground state” basicity for the NO group. For five p‐substituted nitrosobenzenes Δv values are correlated by σ+ substituent constants. Trans‐dimeric C‐nitroso compounds form stronger hydrogen bonds than the corresponding monomers, resulting in a shift of the monomer‐trans‐‐dimer equilibrium upon addition of a proton donor like phenol.
Aromatic sulfonation. Part 24: Kinetics and mechanism of the sulfonation of o‐ and m‐xylene in aqueous sulfuric acid
Authors: Prinsen A. J. , Cerfontain H. 
Published: September 2010

AbstractThe sulfonation of o‐ and m‐xylene in concentrated aqueous sulfuric acid has been investigated. Rates and isomer distributions have been measured. The results are discussed in terms of two sulfonating mechanisms. The isomer distributions at 25.0° for the mechanism with H2S2O7 as sulfonating entity are 45.1 ± 0.4% 3‐ and 54.9 ± 0.4% 4‐substitution for o‐xylene, and 14.5 ± 0.6% 2‐, 84.3 ± 0.6% 4‐ and 1.2 ± 0.2% 5‐substitution for m‐xylene. For the mechanism with H3SO4+ as sulfonating entity these data are 6.5 ± 0.9%, 3‐ and 93.5 ± 0.9% 4‐substitution with o‐xylene, and 0.5 ± 0.2% 2‐, 98.9 ± 0.4% 4‐ and 0.6 ± 0.2% 5‐substitution with m‐xylene. The smaller degree of 3‐substitution with o‐xylene for the H2S2O7 ‐ as compared with the H3SO4+ ‐ mechanism is mainly due to a difference in entropy of activation. The former mechanism encounters more steric hindrance than the latter on substitution ortho to a methyl group. The experimental partial rate factors for the three isomeric xylenes for the two sulfonation mechanisms differ by less than a factor of 4 from those calculated on the basis of additivity of substituent effects with the exception of the 2‐position of m‐xylene, for sulfonation by the entity H3SO4+, and of the 2‐ and 4‐positions of m‐xylene for sulfonation by the entity H2S2O7.
Oxidative coupling of alkyl‐substituted catechols with phloroacylophenones
Authors: Overeem J. C. 
Published: September 2010

AbstractOxidative coupling of 4‐methylcatechol with phloroacetophenone and methylphloroacetophenone leads to 6‐acetyl‐4,4a‐dihydro‐7,9‐dihydroxy‐4a‐methyl‐2,3‐dibenzofurandione (Ie) and 6‐acetyl‐4,4a‐dihydro‐7,9‐dihydroxy‐4a,8‐dimethyl‐2,3‐dibenzofurandione (IIe), respectively.The same type of compound is formed when using 3,5‐dimethyl, 3,4‐di‐methyl‐ or 3,4,6‐trimethyl‐catechols instead of 4‐methylcatechol. However, 3,4‐dimethyl‐ and 3,4,6‐trimethyl‐catechols give mainly compounds which are derivatives of 2(4aH)‐dibenzofuranone.
Aromatic sulfonation 25: Kinetics and mechanism of the sulfonation of fluoro‐, bromo‐ and iodo‐benzene in aqueous sulfuric acid
Authors: Kort C. W. F. , Cerfontain H. 
Published: September 2010

AbstractRates and isomer distributions have been determined for the sulfonation of fluoro‐, bromo‐ and iodo‐benzene in 83‐98% sulfuric acid at 25°. The results are analogous to those for chlorobenzene 1. It is shown that the mechanism proposed previously1 is incorrect The σ‐complex formed in the rate‐limiting reaction of ArH with H2S2O7 is not magnified image
The conformation of non‐aromatic ring compounds 53: The crystal structure of 22,23‐dibromo‐9β‐ergost‐4‐en‐3‐one (Determined at ‐180°C and at 20°C)
Authors: Hesper B. , Geise H. J. , Romers C. 
Published: September 2010

AbstractThe compound 22,23‐dibromo‐9β‐ergost‐4‐en‐3‐one crystallizes in the orthorhombic space group P212121 with four molecules per unit cell. Lattice constants measured at ‐ 180° are a = 34.19, b = 12.44 and c = 6.09 Å. The structure was solved by the heavy‐atom technique refined by the method of least squares, the final R value being 9.6%.This steroid molecule belonging to the 8β, 9β,10β‐series has a cis‐B/C junction which gives rise to unusual twist‐boat conformations for rings B and C. An explanation is given in terms of torsional angles. The conformation of ring D is nearly a C13 envelope.
Preparation, properties and absolute configuration of (‐)‐allantoin
Authors: 's‐Gravenmade E. J. , Vogels G. D. , van Pelt Corry 
Published: September 2010

AbstractA procedure is given for the preparation and isolation of (‐)‐allantoin (5‐ureidohydantoin). A grown culture of Pseudomonas aeruginosa was incubated with (±)‐allantoin at pH 6. (+)‐Allantoin was degraded by the bacteria and (‐)‐allantoin was removed from the medium with the aid of activated carbon.Several properties of (‐)‐allantoin were determined: solubility and molar rotation in various solvents, infrared spectrum, decomposition point and dependence of the molar rotation on pH. The properties were compared with those of (±)‐allantoin, R‐ and S‐hydantoin‐5‐acetic acid.From circular dichroism measurements of (‐)‐allantoin, S‐hydantoin‐5‐acetic acid and R‐carbamoylalanine it was concluded that (‐)‐allantoin is R‐allantoin.
Hydrolysis and racemization of allantoin
Authors: Vogels G. D. , de Windt F. E. , Bassie W. 
Published: September 2010

AbstractThe rates of hydrolysis and racemization of allantoin (5‐ureidohydantoin) were measured as a function of pH and temperature. Both reactions are susceptible to acid and base catalysis. Spontaneous hydrolysis of the neutral and anionic forms of allantoin determines the rate‐pH profile at pH values from 2 to 13.Allantoin is converted to allantoate (diureidoacetate) which is transformed to glyoxylate and urea in acid media. At pH values ∼ 3 ammonia is formed directly from the ureido grouping of allantoin.The rates of racemization of (‐)‐allantoin and of L(‐)‐ and D(+)‐hydantoin‐5‐acetic acid were compared. Both reactions involved most probably enolization of the moiety of the hydantoin rings.
Hydrolysis of allantoate
Authors: Vogels G. D. , van Der Drift C. 
Published: September 2010

AbstractThe rate of hydrolysis of allantoate (diureidoacetate) was measured as a function of temperature and pH. Similar experiments were performed with urea and N‐carbamoylglycine (hydantoate) and the results were compared. At pH values below 7 allantoate was converted to ureidoglycolate and urea. The equilibrium position of this conversion was determined as a function of temperature. In alkaline media isocyanate, ammonia, glyoxylate and urea were formed from allantoate. The reaction rate of this conversion was similar to those measured in urea and N‐carbamoylglycine hydrolyses.
A gas‐chromatographic investigation of the thermodynamics of solutions of monosubstituted hexane, cyclohexane, benzene and pyridine derivatives and of some tetra‐alkyl compounds in apiezon M
Authors: Hammers W. E. , de Ligny C. L. 
Published: September 2010

AbstractFrom retention volumes, determined over a range of temperatures, standard partial molar free enthalpies, enthalpies and entropies of vaporization from infinitely dilute solution in apiezon M are calculated and discussed. Particular attention is paid to the possibility of restricted molecular rotation of the solute molecules, the validity of Butler's additivity rule for the free enthalpy of vaporization and the applicability of the regular solution theory to the enthalpy of mixing of the liquid solutes with apiezon.
Complexes with ligands containing the carbonyl group. Part I: Complexes with acetone of some divalent metals containing tetrachloro‐ferrate(III) and ‐indate(III) anions
Authors: Driessen W. L. , Groeneveld W. L. 
Published: September 2010

AbstractA series of new complexes is reported with acetone as the ligand: viz. [M(CH3COCH3)62+][A−]2 where M is Mg(II), Ca(II), Sr(II), Mn(II), Fe(II), Co(II), Ni(II), and Zn(II); and A− is FeCl−4 and InCl−4.In the complexes, the carbonyl vibration is shifted to lower frequencies and the CO bending, the CO deformation, and the CCC deformation vibrations are shifted to higher frequencies with regard to the vibrations in the free ligand. The magnitudes of the shifts are dependent on the metal ions. In the far infrared a metal‐dependent absorption band appears, which is attributed to the metal‐ligand stretching vibration.Investigation of ligand field spectra indicates the presence of octahedral species M(acetone)62+ in the solid compounds. Values for Dq and B′ are reported and the ligand is placed in the spectrochemical and nephelauxetic series.
Synthesis of the sequence of oxytocin on a hydroxymethylstyrene‐divinylbenzene polymer
Authors: Beyerman H. C. , in 'T Veld R. A. 
Published: September 2010

AbstractThe preparation of a hydroxymethylstyrene‐2%‐divinylbenzene polymer is described.The optimal method for the esterification of this polymer with N‐t‐butoxy‐carbonyl amino acids was found by using N,N′‐carbonyldiimidazole, the remaining hydroxyl groups being protected by formation of their acetates.On this polymer the nonapeptide sequence of the hormone oxytocin was synthesized and then split off in two ways. Tertiary base‐catalysed methanolysis (found in this Laboratory) gave the nonapeptide methyl ester: Z‐Cys(BZL)‐Tyr‐Ile‐Gln‐Asn‐Cys(BZL)‐Pro‐Leu‐Gly‐OMe a. L‐Amino acids are meant. b. Abbreviations used here and later: IUPAC, Information Bulletin 25, February 1966, 32‐40; 26, August 1966, 11‐19; 27, December 1966, 16‐18; 30, October 1967, 27‐32.
, and ammoniacal methanol gave the carboxy‐terminal amide: Cys(BZL)‐Tyr‐Ile‐Gln‐Asn‐Cys(BZL)‐Pro‐Leu‐Gly‐NH2(H2O · HBr).The usual debenzylation and cyclization of the amide gave biologically active material.
A chelate of ZnCl2 with ethylenediiminobisacetylacetone
Authors: Bellaart A. C. , van den Dungen G. J. , Kuijer M. , Verbeek J. L. 
Published: September 2010

AbstractUnsuccessful attempts to prepare ethylenediiminobisacetylacetonezinc led to the isolation of a novel compound ethylenediiminobisacetylacetonezinc dichloride following a procedure similar to that introduced by Ramaiah and MartinK. Ramaiah and D. F. Martin, J. Inorg. Nucl. Chem. 27, 1663 (1965).
. A tentative structure of ethylenediiminobisacetylacetonezinc dichloride is proposed from UV, IR, NMR, and conductance data.
Ring transformations in reactions of heterocyclic halogeno compounds with nucleophiles (XVIII): Pyrimidines (XVIII). D/H exchange studies during the conversion of 2‐substituted 4‐chloropyrimidines into 2‐substituted 4‐methyl‐s‐triazines by treatment with potassium amide in liquid ammonia
Authors: van der Plas H. C. , Zuurdeeg B. , van Meeteren H. W. 
Published: September 2010

Abstract4‐Chloro derivatives of 2‐piperidino‐ and 2‐morpholinopyrimidine are converted by potassium amide in liquid ammonia into 2‐piperidino‐ and 2‐morpholino‐4‐methyl‐s‐triazine, respectively, in about 80‐85% yield. From the results of the reactions of the 6‐monodeuterio and the 5,6‐dideuterio derivatives of 4‐chloro‐2‐morpholinopyrimidine with the same reagent it has been concluded that during the reaction course an intermediate must be present which contains an acidic hydrogen. An acetylenic intermediate is proposed.
Formation of acetylenic dithioesters from substituted allenyl vinyl sulfides: A new type of thio‐claisen rearrangement
Authors: Schuijl P. J. W. , Brandsma L. 
Published: September 2010

AbstractThe ketene dithioacetals CH2C(SC2H5)SC(R)CCH2 (with R  H or C2H5) are converted into acetylenic dithioesters RC ≡ CCH2CH2C(S)SC2H5 upon heating at 80–110°. The starting compounds are prepared by treating the ketene dithioacetals H2CC(SC2H5)SC≡CCH3 with lithium amide in liquid ammonia and subsequently hydrolysing with water or alkylating with ethyl bromide.
A voltammetric study of the diffusion of ferrocyanide ion in aqueous solution
Authors: Powell F. E. 
Published: September 2010

AbstractIn a voltammetric study of the diffusion of ferrocyanide ion to a platinum microelectrode at 25°C the diffusion area is calculated from the Cottrell equation in the case of chronoamperometry, and from the Sand equation, in the case of chronopotentiometry. The values obtained are used to calculate the relative diffusion coefficients of the ion at other temperatures.
Deazapurine derivatives. V: A new synthesis of 1‐ and 3‐deaza‐adenine and related compounds
Authors: de Roos K. B. , Salemink C. A. 
Published: September 2010

AbstractReinvestigation of the cyclization of 2,3,4‐triaminopyridine (1) by several procedures showed that both 7‐aminoimidazo[4,5‐b]pyridine (1‐deaza‐adenine, II) and 4‐aminoimidazo[4,5‐c]pyridine (3‐deaza‐adenine, III) were always obtained. A new and convenient route to the synthesis of II has been devised. Also an unambiguous synthesis of III is given. Ring closure of 2,4,5‐triamino‐pyridine (XIX) afforded 6‐aminoimidazo[4,5‐c]pyridine (3‐deazaisoadenine, XX).
Electrochemical reduction of AZA aromatics: Part II. Protonation products of di‐aza aromatics
Authors: van Der Meer D. 
Published: September 2010

AbstractThe formation of proton products plays an essential part in the explanation of the reduction mechanism of the di‐aza aromatics in dimethylformamide (DMF). By recording cyclic polarograms of the di‐aza aromatics and comparing them with those obtained from the protonated products of the di‐aza aromatics it is sometimes possible to identify the proton products which are formed in the reduction process. From the experimental evidence and from calculations by means of the HMO method it can be shown that protonation of the mononegative ions is the first step in the dimerization of quinazoline, phthalazine and pyrimidine.
Derivatives of furan and 2,5‐dihydrofuran from cumulenic carbinol ethers
Authors: Rompes J. A. , Hoff S. , Montijn P. P. , Brandsma L. , Arens J. F. 
Published: September 2010

AbstractTreatment of the carbinols (CH3)2C=C=C=C(OCH3)CR1R2(OH) (I) with potassium tert‐butoxide in dimethyl sulfoxide gives derivatives of furan (III) if R2 = H and derivatives of 2,5‐dihydrofuran (II) if R1 and R2 are both alkyl or if R1R2C = cyclohexyl. Acid‐catalysed hydrolysis of II and III affords derivatives of 3‐oxo‐2,3‐dihydrofuran (IV).Potassium amide in liquid ammonia, when used in excess, causes isomerisation of I into CH2=C(CH3)CH=C=C(OCH3)CR1R2(OH) (Ia).
Deazapurine derivatives. VI: Synthesis of 1,2,5‐thia‐ and 1,2,5‐selena‐diazolopyridines
Authors: Harts G. H. , de Roos K. B. , Salemink C. A. 
Published: September 2010

Abstract1,2,5‐Thiadiazolo[3,4‐b]‐ and 1,2,5‐thiadiazolo[3,4‐c]‐pyridines have been synthesized from the appropriate diaminopyridines and thionyl chloride. Ring closure of the diamines with selenious acid gave the corresponding selenadiazolopyridines.
Stereochemistry of base‐catalysed double‐bond migration in allyl ethers
Authors: Kloosterziel H. , van Drunen J. A. A. 
Published: September 2010

AbstractBase‐catalysed isomerization of trans‐3‐methoxy‐1‐phenylpropene (A) yields stereospecifically as the initial product cis‐1‐methoxy‐3‐phenylpropene (B). This is caused by the (intermediate) formation of the cis‐1‐methoxy‐trans‐3‐phenylallyl anion (II‐1), which is energetically favoured over the trans‐isomeric anion (I). The NMR spectra of I and II‐1 are described.
Stereochemistry of base‐catalysed double‐bond migration in inner olefins
Authors: Kloosterziel H. , van Drunen J. A. A. 
Published: September 2010

AbstractThe mechanism of the title reaction is discussed. The NMR spectra of the 1‐methyl‐ and 1,3‐dimethyl‐1‐phenylallyl and of the 3‐methyl‐ and 1,3‐dimethyl‐oxapentadienyl anions are given.
Protonation of 9‐ethyl‐10‐methylanthracene: Absence of a large Baker‐Nathan effect in alkylarenium‐ion formation
Authors: Brouwer D. M. , van Doorn J. A. 
Published: September 2010

AbstractProtonation of 9‐ethyl‐10‐methylanthracene in HF or CF3COOH/H2O · BF3 affords a mixture of the 9H+‐ and 10H+‐9‐ethyl‐10‐methylanthracenium ions. These ions differ in free energy by only 0.9‐1.0 kcal · mole−1. This small difference in stability, which is probably due to steric rather than electronic effects, shows that methyl and ethyl groups are approximately equally effective in stabilizing arenium ions. This result demonstrates, contrary to what was recently concluded1 on the basis of calorimetric measurements of the heats of protonation of alkylbenzenes in FSO3HSbF5, that there is no large Baker‐Nathan effect in alkylarenium‐ion formation.The PMR‐spectrum of the 9H+‐9‐ethyl‐10‐methylanthracenium ion exhibits some remarkable features ‐ notably an unusually strong shielding of the ethyl‐CH3 protons · that are associated with the particular conformation of the (>CHCH2CH3) group in this ion and related ones.
Enolization and oxidation: I. The reaction of 3‐hydroxy‐2‐butanone with ferricenium ions in an acidic medium
Authors: Lubach J. , Drenth W. 
Published: September 2010

AbstractOxidation of 3‐hydroxy‐2‐butanone, CH3COCHOHCH3 to 2,3‐butanedione, CH3COCOCH3, by ferricenium cations, Fe(C5H5)2⊕, has been studied in acidic 50 vol % aqueous ethanol. At ferricenium ion concentrations above 0.5 × 10−3 mole · l−1 the rate of reaction is independent of this concentration. Enolization is suggested to be rate determining. The influence of acid concentration and of oxygen has been studied.
C‐nitroso compounds. Part XII: Cis‐ and trans‐azodioxy compounds (dimeric nitroso compounds) by photochemical nitrosation of hydrocarbons with tert‐butyl nitrite
Authors: Mackor A. , de Boer Th. J. 
Published: September 2010

AbstractThe photochemical nitrosation of (cyclo)alkanes and alkylbenzenes, containing abstractable primary or secondary hydrogen atoms, with t‐butyl nitrite has been carried out at 0‐5°C using wavelengths around 400 nm. The main products are trans‐azodioxy compounds (trans‐dimeric nitroso compounds), derived from the solvent and the corresponding oximes in (total) yields, ranging from 55‐80%. At low temperature or with high‐energy light sources it is possible to isolate the cis‐compounds in low yields (up to 30%).
Structure and physical properties of aluminium alkoxides. Part II: Changes in physical properties of liquid aluminium isopropoxide during storage
Authors: Fieggen W. , Gerding H. 
Published: September 2010

AbstractThe density, refractive index, dielectric constant and viscosity of liquid aluminium isopropoxide have been studied.From observations for the liquid at 25°, immediately after heating at 130° and cooling rapidly, an Onsager dipole moment of 1.7‐2.5 D is calculated.During storage the physical properties change slowly. This confirms the occurrence of a molecular rearrangement reaction, which was inferred previously from molecular weight and NMR data. A further indication was obtained by the discovery of a second solid form of aluminium isopropoxide, which melts at 29.5°, whereas we have found also a form with melting point of about 137°, considerably higher than that for normal aluminium isopropoxide, 118°.The rates of changes in density and viscosity have been measured at different temperatures, from which the activation energy for the rearrangement reaction is estimated to be about 12 kcal/mole.
The importance of orbital orientation as a rate‐controlling factor in intramolecular reactions of carbonium ions
Authors: Brouwer D. M. , Hogeveen H. 
Published: September 2010

AbstractIn carbonium ions the relative orientation of the vacantp‐orbital of the electron‐deficient carbon atom and the C‐H and C‐R bonds at the adjacent carbon atom (“orbital orientation”) is a very important factor for the rates of 1,2‐hydride and alkyl shifts and of cleavage of β C‐C bonds. A large number of examples of this effect can be found among the reactions of directly observable carbonium ions. In some cases it causes the rate of a 1,2‐shift or a β‐cleavage in a cyclic carbonium ion to be several orders of magnitude lower than in acyclic carbonium ions.
The trans‐1‐methylpentadienyl anion ‐ the charge‐repelling effect of the methyl group
Authors: Kloosterziel H. , van Drunen J. A. A. 
Published: September 2010

AbstractThe title anion and its rapid isomerization to the cis‐isomer have been observed with the aid of NMR spectroscopy. The difference in charge‐repelling capacity observed between the trans‐ and cis‐methyl groups is discussed.
Copper(II) alkyl isocyanide complexes
Authors: Stephany R. W. , Drenth W. 
Published: September 2010

AbstractThe first synthesis, isolation and characterization of four copper(II) isocyanide complexes are described, [Cu(CNR)4(H2O)2]X2 with R = tert‐butyl and 1,1,3,3‐tetramethylbutyl, and XClO4⊖ and BF4⊖.Decomposition of these complexes leads to copper(I) derivatives. One of them could be characterized as [Cu(CN‐t‐C4H9)4](ClO4). Infrared, electron spin resonance, and some X‐ray data are provided.
The conformation of non‐aromatic ring compounds. Part 60. The crystal structure of 2‐p‐Chlorophenyl‐1,3‐dioxane
Authors: de Kok A. J. , Romers C. 
Published: September 2010

AbstractCrystals of 2‐p‐chlorophenyl‐l,3‐dioxane are triclinic. The space group is P1¯. The unit cell containing two molecules has dimensions a = 9.708, b = 10.914, c = 4.740 Å, α = 90.7, β = 102.6 and γ = 103.1°.Photographic X‐ray reflexion data (copper radiation) were recorded about two axes. The structure was solved by Patterson methods and refined by a least‐squares technique. The intramolecular bond distances and valency angles do not deviate from the expected values. The phenyl group is in equatorial orientation with respect to the chair‐shaped dioxane ring. The O‐C‐O part of the dioxane molecule is more puckered (average torsional angle 62.5°) than the corresponding cyclohexane ring; the values found for the torsional angles are in agreement with model studies and NMR measurements.
NMR spectra of some cyclic dienyl anions
Authors: Kloosterziel H. , van Drunen J. A. A. 
Published: September 2010

AbstractThe NMR spectra of the cyclohexadienyl anion 5 and of the cyclo‐octadienyl anion 7 have been studied. The strongly bent anion 7 shows at low temperatures reversible line broadening. At higher temperatures 7 electrocyclizes to the bicyclo[3.3.0]octenyl anion. It is concluded that in neither of these anions there is substantial 1,5 overlap (homoaromaticity).