Showing papers in "Australian Journal of Chemistry in 1987"
TL;DR: In this paper, solid state and solution 31P n.m. spectra reveal single broad resonance lines for X = NO3 (chemical shift 19 ppm, ref. 85% H3PO4), CH3C02 (24 ppm), SCN (36ppm), CN (37 ppm ), CH3 (47 ppm ) and CH3(47 ppm ), the latter three spectra being recorded at 121.47 MHz and 161.96 MHz, respectively.
Abstract: Linear, two-coordinate compounds of molecular formula (PPh3) AuX have been characterized by solid-state and solution 31P n.m.r. spectroscopy, and single-crystal X-ray diffraction techniques. The solid state n.m.r. spectra reveal single, broad resonance lines for X = NO3 (chemical shift 19 ppm , ref. 85% H3PO4), CH3C02 (24 ppm), SCN (36ppm), CN (37 ppm ) and CH3 (47 ppm ) and doublets for X = Cl (27, 33 ppm ), Br (28, 36 ppm ) and I (34, 38 ppm ), the latter three spectra being recorded at 121.47 MHz and 161.96 MHz. Solution spectra show relatively sharp single resonances for each compound with 6 values generally slightly higher than in the solid state. Crystal data are reported for X = NO3, space gro )p P21/c, a 8 895(9), b 10.117(8), c 19.57(2) A; β 97.43(8)o, Au-P,O = 2.199(5), 2.02(1) A. Crystals of compounds with X = Br, I and SCN are isomorphous with the AuCl compound, belonging to space group 212121. For X = Br, a 12.479(5), b 13.45(1), c 10.0!2(8) A; Au-P, Br = 2.252(6), 2.407(2) A. For X = I, a 12.529(8), b 13.870(5), c 10.188(4) A; Au-P, I = 2.254(5), 2.556(2) A. For X = SCN, a 12.257(5), b 13.776(8), c 10.754(6) A; Au-P, S = 2.252(7), 2.304(7) A.
54 citations
TL;DR: In this paper, the rate constants and activation parameters for cyclization were determined by kinetic e.s.r. spectroscopy for various radicals, including hex-5-enyl, trialkylgermanium, and 2,2-dimethylbut-3-enoyloxymethyl radicals.
Abstract: The hex-5-enyl (1), 3-oxahex-5-enyl (6), 2-oxahex-5-enyl (9) and 2,2-dimethylbut-3- enoyloxymethyl (13) radicals have been generated by interaction of the corresponding bromides with trialkyltin or trialkylgermanium radicals, and their rate constants and activation parameters for cyclization have been determined by kinetic e.s.r . spectroscopy. The 3-oxa species (6) undergo 1,5-ring closure more rapidly than does hex-5-enyl radical (1) because of favourable stereoelectronic factors. Spectral evidence has been obtained for restricted rotation about the O-CH2* bond in the 2-oxa radical (9) as a consequence of which its ring closure is relatively slow. Similarly, 1,5-ring closure of the ester derived radical (13) is slow because of unfavourable conformational effects arising from restricted rotation about the CO-O bond. The radical (22) formed from allyl bromoacetate does not undergo ring closure. Spectral data have been obtained for various radicals (16), (19), (23), (24) formed by intermolecular addition.
54 citations
TL;DR: In this paper, a single-crystal X-ray diffraction study was performed on a bis-complex of Sn(OPri)2(acac)2 and Sn(Opri)4.
Abstract: Tin(IV) alkoxides react with pentane-2,4-dione (acetylacetone) and other β-diketones to yield Sn(OR)3(chel) or Sn(OR)2(chel)2 derivatives. Sn(Opri)3(acac) has been shown to be dimeric in the solid state by a single-crystal X-ray diffraction study, the tin atoms being linked by two alkoxide bridges. In solution l19sn n.m.r. spectral data show that this single complex rapidly converts into a mixture of tin-containing species followed by slow disproportionation to the bis derivative Sn(OPri)2(acac)2 and Sn(Opri)4. The bis complexes Sn(OR)2(acac)2 appear to exist predominantly in solution with cis arrangements of alkoxide groups even when OBut or 2,2,6,6-tetramethylheptane-3,5-dione (dipivaloylmethane) are present.
51 citations
TL;DR: In this article, the synthesis of the title compound, isolated from the brown kelp ( Ecklonia radiata ) or the giant clam (Tridacna maxima), is reported.
Abstract: The synthesis of the title compound, isolated from the brown kelp ( Ecklonia radiata ) or the giant clam (Tridacna maxima), is reported. Glycosidation of 1-O-acetyl-2,3,5-tri- O- benzoyl -β-D-ribose, either directly with (S)-1,2-di-O-benzylglycerol or via the derived orthoester with (S)-1,2-O-isopropylideneglycerol, led to two fully protected glycerol β-D- ribofuranosides. Subsequent chemical manipulations led to a common intermediate having a free hydroxy group at C5 of the D-ribose residue. Replacement of this hydroxy group by a chlorine atom allowed the introduction of the dimethylarsinyl group at C5 in a two-step procedure, and removal of protecting groups provided the natural product.
48 citations
TL;DR: 1,l'-oxalylbisisatin has been prepared and converted readily into a wide range of glyoxylic esters and amides from which the macrocyclic metal complexes (11)-(16) have been obtained as discussed by the authors.
Abstract: 1,l'-Oxalylbisisatin (7) has been prepared and converted readily into a wide range of glyoxylic esters and amides (10) from which the macrocyclic metal complexes (11)-(16) have been obtained.
47 citations
TL;DR: A 17-membered O2N3-donor macrocycle has been applied to a derivatized silica gel substrate, and the binding and selectivity properties of the functionalized surface towards CO11, Ni11 CU11, Zn11 and Cd11 in aqueous solution have been investigated as mentioned in this paper.
Abstract: A 17-membered O2N3-donor macrocycle has been appended to a derivatized silica gel substrate, and the binding and selectivity properties of the functionalized surface towards CO11, Ni11 CU11, Zn11 and Cd11 in aqueous solution have been investigated. Metal uptake was found to be concentration-dependent with the maximun (saturation) loading capacity in all cases being less than the 'theoretical' amount based on the calculated degree of polymer functionalization present. Metal loading and leaching both occurred readily in aqueous media; the loading studies were performed at near-neutral pH whereas metal leaching was carried out by using either dilute (hydrochloric) acid or aqueous ammonia solution. The functionalized silica underwent no degradation during repeated loading/leaching cycles, and, under similar conditions, its binding capacity is highest for CU11 relative to the other ions investigated. The observed binding order was CO11 ZnIIand this sequence parallels the respective log K values for the complexes of the free macrocycle. However, the loading order of ZnII > CdII which was observed is the opposite to the corresponding log K values for the unattached complexes. Steric effects involving the silica backbone appear to influence the binding in this case. The insolubilized product may be used to remove selectively CuII in the presence of the other ions mentioned above.
46 citations
TL;DR: The dependence of the rate of CO2 formation follows the simple Langmuir expression:R(CO2)=k1k2[s]/(1+k1[s]) as mentioned in this paper.
Abstract: The oxidation of a number of aromatic compounds to carbon dioxide by exposure to near U.V. light in aqueous titanium dioxide suspensions has been studied as a function of the solute concentration. In most, the dependence of the rate of CO2 formation follows the simple Langmuir expression:R(CO2)=k1k2[s]/(1+k1[s])The rate is essentially independent of concentration above 200 µM and becomes progressively more dependent on the concentration as it decreases. Changes in the mineralization rate are most clearly reflected in k2, the parameter determined by the limiting rate at high concentrations. A consequence of the dependence is that total mineralization is strictly never achieved but is approached asymptotically at extended illumination times. The expression and parameters are given which enable the prediction of the extent of mineralization over a wide range of concentrations. The solutes studied were benzene, benzoic acid, benzoate ion, salicylate ion, phenol, chlorobenzene , aniline, anilinium ion, nitrobenzene, chloroform and formic acid. It was confirmed that pH and oxygen concentration affect the rate of carbon dioxide formation but, in the photochemical reactor used, the rate was not significantly affected by the amount of TiO2 suspended for loadings from 0.05 to 0.40 g per 400 ml.
44 citations
TL;DR: In this paper, the bzs-watersystem was investigated by chemical, X-ray and thermal analyses, and four discrete lower hydrates, namely, the tetra-, tri-, mono-and hemi-hydrates, and an anhydrate were derived from the pentahydrate.
Abstract: The bzs-watersystem, where bzs is an abbreviation for ZnSO4.3Zn(OH)2, has been investigated by chemical, X-ray and thermal analyses. The bzs.5H2O was precipitated from solution. Four discrete lower hydrates, namely, the tetra-, tri-, mono- and hemi-hydrates, and an anhydrate were derived from the pentahydrate . The tetra- and tri-hydrates could be prepared by dehydration of the pentahydrate, either thermally or over desiccants; the monohydrate could only be prepared by dehydration of the higher hydrates over desiccants; the hemihydrate and anhydrate could only be prepared by thermal dehydration. Thermal dehydration of the pentahydrate to compositions between the tri- and hemihydrates resulted in the formation of intergrowth structures. Evidence is provided that the layer structure of the pentahydrate persists throughout the series until dehydroxylation of the anhydrate commences. X-ray powder data for the discrete phases have been indexed.
42 citations
TL;DR: In this article, the HeI photoelectron spectra of pentane-2,4-dione measured at various temperatures have been subjected to a spectrum-stripping technique to enable isolation of the complete HeI photelectron spectrum of the keto and enol tautomers.
Abstract: The HeI photoelectron spectra of pentane-2,4-dione measured at various temperatures have been subjected to a spectrum-stripping technique to enable isolation of the complete HeI photoelectron spectra of the keto and enol tautomers. The resulting spectrum-stripping coefficients allow evaluation of the enolization equilibrium constant at each temperature and subsequently the enthalpy of enolization. Interpretation of the photoelectron spectra is achieved with the use of ab initio molecular orbital calculations. Photoionization of non-bonding oxygen, and π -type electrons, contribute to the low ionization energy region of the spectrum, with a πCC < no- <πCO ordering for the enol tautpmer , and no- < no+ < πCO+ for the keto tautomer . Because of different electronic relaxation effects, ∆SCF calculations are required to predict correctly the observed πCC/no- spacing for the enol tautomer.
39 citations
TL;DR: In this paper, the condensation reaction of (3,7-diazanonane-1,9-diamine)copper(II) with formaldehyde and nitroethane in basic methanol is highly specific.
Abstract: The condensation reaction of (3,7-diazanonane-1,9-diamine)copper(II) with formaldehyde and nitroethane in basic methanol is highly specific, producing the macromonocyclic complex (6-methyl-6-nitro-1,4,8,11-tetraazacyclotetradecane)copper(II) as the only product. However, under conditions employed, the reaction cannot be readily driven to completion, and an intermediate consisting of equimolar amounts of precursor and product complexes can be crystallized preferentially. The intermeciate crystallizes in the monoclinic space group P 21/c, a 16.11 5(10), b 8 825(6), c 25.970(13)A, β 104.30(4)o, and consists of a linear polymer of the two alternating copper(II) complexes bridged by perchlorate anions; 3372 'observed' reflections were refined to a residual of 0.049. Each copper ion is surrounded by a square-planar arrangement of four nitrogen donors, with perchlorate oxygens from bridging ions occupying the axial sites. The Cu-N distances in the precursor tetraamine unit (1.991 to 2.006 A) and the product macromonocycle unit (1.995 to 2.017 A) are similar; apparently the copper ion is readily accommodated in both the precursor and the 14-membered macrocycle. Reduction of the nitro group of the macrocycle by zinc/aqueous acid produces the corresponding ligand with a pendant primary amine group, isolated as the copper(II) complex. Complexes were characterized by infrared and electronic spectroscopy, and voltammetry.
39 citations
TL;DR: In this article, the crystal structures of the methylxanthates of AsIII (two polymorphs), sbIII and BiIII are reported, and the structures are solved by normal Fourier methods and refined by a full-matrix least-squares procedure in each case on reflections which satisfied the I ≥ 2.5σ(I) criterion.
Abstract: The crystal structures of the methylxanthates of AsIII (two polymorphs), sbIII and BiIII are reported. In the monoclinic form of As(S2COCH3)3 the molecular threefold symmetry, as found in the previously reported trigonal As(S2COCH3)3, is not crystallographically imposed. The distorted octahedral environments about each of the ASIII centres is defined by three asymmetrically chelating xanthate ligands. In contrast, the sbIIIand BiIII analogues adopt different stereochemistries based on pseudo-m symmetry. In addition, the Sb (S2COCH3)3 and Bi(S2COCH3)3 molecules associate to form loosely held dimers , through weak intermolecular Me…S interactions, in their respective crystal lattices. Crystals of β-As(S2COCH3)3 are monoclinic, P21/c, with unit cell parameters a 14.816(4), b 9.641(6), c 21.255(6) A, β 90.18(2)o, Z = 8. The antimony and bismuth compounds are isomorphous, crystallizing in the triclinic space group P1, with cell dimensions (bismuth details given second) a 5.904(1), 5.924(3); b 10.4891(8), 10.499(3); c 12.3635(9), 12.485(4) A; α 95.993(6), 95.99(3); β 100.92(1), 101.76(4); γ 99.04(1), 101.45(4)o; Z = 2, 2. The structures were solved by normal Fourier methods and refined by a full-matrix least-squares procedure in each case on reflections which satisfied the I ≥2.5σ(I) criterion. Final refinement details for the β arsenic (antimony, bismuth) compounds: R 0.034 (0.027, 0.055), Rw 0.034 (0.029, 0.052) for 2777 (2115, 1894) reflections.
TL;DR: Amathia wilsoni has yielded amathamides C-F, four new bromine-containing alkaloids, which are closely related in structure to the previously described amathamide A and B as mentioned in this paper.
Abstract: Further investigations of the bryozoan Amathia wilsoni have yielded amathamides C-F, four new bromine-containing alkaloids, which are closely related in structure to the previously described amathamides A and B. There is no significant variation in the alkaloid content of different colonies of the bryozoan at the same location, but differences occur between samples of the bryozoan which have been obtained from different collection sites.
TL;DR: The trisulfide analogue of gliotoxin has been purified and characterized from cultures of Penicillium terlikowskii, and has been shown to be present in cultures of the pathogenic fungus Aspergillus fumigatus and the thermophilic fungus Thermoascus crustaceus.
Abstract: The trisulfide analogue (1; n = 3) of gliotoxin (1; n = 2) has been purified and characterized from cultures of Penicillium terlikowskii , and has also been shown to be present in cultures of the pathogenic fungus Aspergillus fumigatus and the thermophilic fungus Thermoascus crustaceus. This compound is equipotent with gliotoxin in a macrophage cell adherence assay confirming earlier results on crude preparations of the compound from A.fumigatus . The compound has been named gliotoxin -E by analogy with sporidesmin-E.
TL;DR: The depsidones divaronic acid (24) (8-hydroxy-3-methoxy-1,6-dipropyl-11- oxo -11H- dibenzo [ b,e ][1,4]dioxepin-7-carboxylic acid) and stenosporonic acid (25) have been prepared by unambiguous synthesis, and have been shown to cooccur with colensoic acid, atranorin and chloroatranorsin in the lichen Paraparmelia
Abstract: The depsidones divaronic acid (24) (8-hydroxy-3-methoxy-1,6-dipropyl-11- oxo -11H- dibenzo [ b,e ][1,4]dioxepin-7-carboxylic acid) and stenosporonic acid (25) (8-hydroxy-3-methoxy-6-pentyl-l-propyl-ll-oxo-l1H-dibenzo[ b,e ][1,4]dioxepin-7-carboxylic acid) have been prepared by unambiguous synthesis, and have been shown to cooccur with colensoic acid, atranorin and chloroatranorin in the lichen Paraparmelia mongaensis. The syntheses employed a novel biomimetic-type approach which involved a Smiles rearrangement of a precursor meta-depside in the key step. This rearrangement has important biosynthetic implications and may account for the natural occurrence of isostructural depside-depsidone pairs.
TL;DR: In this paper, Europium and ytterbium react with bis(pentafluoropheny1)mercury and cyclopentadiene in pyridine to give (C5H5)3M( py ) (M = Eu or Yb ).
Abstract: The complexes, (C5H5)3M( py ) (M = Nd, Sm, Eu or Yb ), (C5H5)2Eu( py ), and (C5H5)2Yb( py )2 have been prepared from the appropriate lanthanoid elements and thallous cyclopentadienide in pyridine, and (C5H5)3M( NCMe ) (M = Nd , Sm or Yb ) and (C5H5)2Yb( NCMe ) from similar reactions in acetonitrile. Ligand exchange or addition has also been used to give (C5H5)3Sm( py ), (C5H5)2Yb( py )2 and (C5H5)2Yb( NCMe ). Ytterbium metal reduces (C5H5)3Yb( py ) in pyridine to (C5H5)2Yb( py )2, which is oxidized back to (C5H5)3Yb( py ) by TI(C5H5). Europium with (C5H5)2Hg in tetrahydrofuran yields (C5H5)3Eu( thf ), and (C5H5)2Eu is not isolated by using an excess of metal. Oxidation of (C5H5)2Eu to (C5H5)3Eu is effected by (C5H5)2Hg in tetrahydrofuran but not by T1(C5H5) in 1,2-dimethoxyethane. Europium and ytterbium react with bis(pentafluoropheny1)mercury and cyclopentadiene in pyridine to give (C5H5)3M( py ) (M = Eu or Yb ).
TL;DR: In this article, the authors performed a polarization propagator analysis of the through-space coupling pathways, at the RPA-INDO level, and numerically analyzed the expression for the TS coupling in terms of projected polarization propagators and perturbators.
Abstract: In order to obtain a deeper insight into the title effect, several compounds with an F atom very close to a C-H of a nearby functional group were synthesized and the relevant couplings measured. The most conspicuous case was that of 8-fluoro-2-hydroxynaphthalene-1-carbaldehyde where a close proximity between the F and H atoms is the result of fluorine-oxygen repulsion and the formation of an intramolecular hydrogen bond between the hydroxyl and carbonyl groups. The experimental four-bond J(F,CHO) coupling is 26.2 Hz. A compound very similar to this one, but without the OH group, was chosen on which to perform a polarization propagator analysis of the through-space (TS) coupling pathways, at the RPA-INDO level. The expression for the TS coupling in terms of the projected polarization propagator and perturbators was numerically analysed. It is found that this coupling is completely dominated by a TS component of the Fermi contact (FC) term, the main features of which are: ( i ) It decays exponentially with the F-H distance; (ii) Its main contribution comes from an electron excitation involving the F lone-pair, the C-H bond of the CHO moiety and its corresponding antibonding orbital;(iii) The π-type lone-pair does not contribute to the TS coupling pathway of the FC term.
TL;DR: In this paper, the synthesis of 16 and 19-membered dibenzo macrocycles incorporating nitrogen together with oxygen and/or sulfur heteroatoms is described, and the X-ray structure of the 17-memered macrocycle containing an O2N2S heteroatom set is described.
Abstract: The syntheses of 16 new 16- to 19-membered dibenzo macrocycles are reported. These rings incorporate nitrogen together with oxygen and/or sulfur heteroatoms . The X-ray structure of the 17-membered macrocycle containing an O2N2S heteroatom set is described.
TL;DR: The crystal structures of tris (η5-cyclopentadienyl) (pyridine) samarium(III), monoclinic, space group P21/c, a 10.906(4), b 8.636(2), c 17.825(3) A, β 96.38(2)o, Z 4, R 0.035 and R, 0.039 for 2677 'observed' reflections have been determined as discussed by the authors.
Abstract: The crystal structures of tris (η5-cyclopentadienyl) (pyridine) samarium(III), monoclinic, space group P21/c, a 10.906(4), b 8.636(2), c 17.825(3) A, β 96.44(2)o, Z 4, R 0.027 and Rw 0.032 for 3619 'observed' reflections, and tris (η5-cyclopentadienyl)(pyridine)neodymium(III), monoclinic, space group P21 / c, a 14-206(4), b 8.619(2), c 15.190(7) A, β 107.38(2)o, Z 4, R 0.035 and R, 0.039 for 2677 'observed' reflections have been determined. Both compounds have pseudotetrahedral geometry with a coordination number of 10 for the lanthanoid metal but there is a difference in the coordination of pyridine and in unit cell packing between the two structures.
TL;DR: The minor iridoid glucosides present in the aerial parts of Barleria lupulina Lindl. ( Acanthaceae) have been identified as ipolamiidoside (7) and the new compound 6-O-acetylshanzhiside methyl ester (3) as discussed by the authors.
Abstract: The minor iridoid glucosides present in the aerial parts of Barleria lupulina Lindl. ( Acanthaceae ) have been identified as ipolamiidoside (7) and the new compound 6-O-acetylshanzhiside methyl ester (3). The structure of (3) was determined by spectroscopic and chemical methods, and was confirmed by a single-crystal X-ray structure determination. Crystals of (3) are orthorhombic P212121, a 43.75(1), b 8.151(3), c 5.695(2) A, Z 4. The crystal structure was determined at 295 K from diffractometer data [I528 reflections with I > 3σ(I)] and refined to a residual of 0.043. Shanzhiside methyl ester (1) and its 6-Oacetyl (3), 8-Oacetyl (2) and 6,8-O,O-diacetyl (4) derivatives, all of which occur in Barleria lupulina, have been found to inhibit the growth of wheat embryos.
TL;DR: In this paper, the luminescence and absorption properties of pyrene, trimethylbyren-1-y1) ammonium chloride (tmpa) and sodium pyrene-1sulfonate (sps) incorporated into the perfluorosulfonates membrane Nafion have been investigated.
Abstract: The luminescence and absorption properties of pyrene, trimethylbyren-1-y1)ammonium chloride (tmpa) and sodium pyrene-1-sulfonate (sps) incorporated into the perfluorosulfonate membrane Nafion have been investigated. Addition of pb2+ induces a redistribution of pyrene molecules from the hydrophilic domains to more hydrophobic domains of the membrane and results in phosphorescence emission. tmpa is shown to bind strongly to the negatively charged sulfonate groups and does not exhibit phosphorescence nor is it displaced by pb2+. The fluorescence emission and absorption characteristics of sps incorporated in Nafion suggest a hydrophilic microenvironment, probably the water cluster region. The electrostatically unfavourable interaction, however, results in excimer formation even at low probe concentrations. Dynamic and steady-state fluorescence quenching measurements provide further insight into the nature of the different regions of Nafion.
TL;DR: In this article, the lead halide PbX2 (X = C1, Br, I) was shown to contain the lead in an essentially octahedral six-coordinate environment, two of the coordination sites being occupied by monodentate pyridine base moieties and four by bridging halogen.
Abstract: Recrystallization of lead(II) halides, PbX2 (X = C1, Br, I), from n- methylpyridine, n = 3, 4, yields crystalline 1 : 2 adducts; these have all been shown by single-crystal X-ray structure determination to contain the lead in an essentially octahedral six-coordinate environment, two of the coordination sites being occupied by monodentate pyridine base moieties and four by bridging halogen, yielding infinite polymeric arrays. For X = Cl, Br, n = 3, the nitrogen atoms lie cis in the coordination sphere; for the other complexes, they are trans. In the two cis complexes, distortion from ideal orthogonal geometry is more substantial than in the trans, possibly indicative of the presence of a sterically active 'lone pair'.
TL;DR: Me2SO has been used for single-crystal X-ray analysis, and the cation geometries have been established from these Xray data as mentioned in this paper, where the mer and s- fac isomers are distinguished by their different labilities in acidic solution, their different infrared and visible absorption spectra, and their different chromatographic behaviour on SP- Sephadex C 25.
Abstract: Addition of dien in slight excess to CrCl3.6H2O in Me2SO (which has been dehydrated at 190oC, then cooled to 170o) produces an isomeric mixture of orange-yellow [Cr( dien )2] Cl3.Me2SO of approximate composition mer 70%; s- fac 30%; u- fac 98% mer ) mixture. All three isomers can be obtained as (Hg2Cl7)3- salts, suitable for single-crystal X-ray analysis, and the cation geometries have been established from these X-ray data. The mer and s- fac isomers are distinguished by their different labilities in acidic solution ( mer is relatively inert, s- fac decomposes rapidly), their different infrared and visible absorption spectra, and their different chromatographic behaviour on SP- Sephadex C-25. However, this latter technique failed to detect the u- fac form and was complicated by the facile decomposition of the s- fac isomer. The mer and s- fac forms isomerize rapidly in Me2SO and the equilibrium is largely towards the mer. [Cr( dpt )2]Cl3 [ dpt = di(3- aminopropyl )amine] could be obtained only by direct reaction between anhydrous CrCl3 and dpt , and was subsequently precipitated as the iodide and perchlorate salts. These consisted entirely of the mer isomer, from their isomorphism with the corresponding mer -[Cr( dpt )2 ]3+ salts. The six-membered rings in -[Cr( dien )2 ]3+ are considerably more resistant to hydrolytic decomposition than the rings in mer -[ cr ( dien )2]3+ and mer -[Co( dpt )2]3+.
TL;DR: Phosphonobaclofen, 3-amino-2-(4-chlorophenyl) propylphosphonic acid, has been synthesized in five steps from ethyl 3-( 4-chloropheny1)-but-2-enoate, and is a specific antagonist of baclofens as discussed by the authors.
Abstract: Phosphonobaclofen, 3-amino-2-(4-chlorophenyl) propylphosphonic acid, has been synthesized in five steps from ethyl 3-(4-chloropheny1)but-2-enoate, and is a specific antagonist of baclofen Two alternative synthetic pathways, involving conjugate addition of phosphite to 2-(4-chlorophenyl) propenenitrile and of cyanide to 2-(4-chlorophenyl) ethenylphosphonate ester, failed Cyanide ion did add efficiently to ethyl 3-(4-chloropheny1)-2-diethoxyphosphinylprop-2- enoate, and hydrogenation followed by hydrolysis of the product gave (2S,3S)- and (2R,3R)-4-amino-3-(4-chloropheny1)-2-phosphonobutanoic acid, which is also undergoing pharmacological evaluation
TL;DR: In this paper, 2'-Chloroacetophenones react with carbon disulfide in the presence of sodium hydride to form 4-hydroxydithiocoumarin anions, which can be tautomerized to 2-mercapto-1-thiochromones by treatment with strong acid.
Abstract: 2'-Chloroacetophenones react with carbon disulfide in the presence of sodium hydride to form 4-hydroxydithiocoumarin anions. Kinetic protonation provides the 4-hydroxydithiocoumarins which can be tautomerized to 2-mercapto-1-thiochromones by treatment with strong acid. Both tautomers are quite stable and do not readily interconvert. Alkylation of either 4-hydroxydithiocoumarin or 2-mercapto-1-thiochromone provides S-alkyl derivatives exclusively while acylation with acid anhydrides gives mixtures of O- and S-acyl products. Oxidation with sodium perborate yields the exocyclic monosulfoxide while m-chloroperbenzoic acid gives the exocyclic sulfone.
TL;DR: The barriers to inversion at a standard temperature (∆G‡;340) ranged from 120 kJ mol-l and showed good correlation with the van der Waals radii of the interacting substituents at C4 and C5 and with the previously proposed 'apparent overlap' parameter.
Abstract: Six 4,5-di-X-9,l0-dihydrophenanthrenes (X = H, F, OCH3, Cl, CH3, CF3) were synthesized and their inversion rates were investigated by n.m.r., spectroscopy. The barriers to inversion at a standard temperature (∆G‡;340) ranged from 120 kJ mol-l and showed good correlation with the van der Waals radii of the interacting substituents at C4 and C5 and with the previously proposed 'apparent overlap' parameter.
TL;DR: In this article, the structure determinations of (LH)2(B10H10), (1), and (L H2)(B 10H10, (2), L = 2,2'- bipyridine, have been carried out by single-crystal X-ray diffraction methods at 295 K, being refined by full-matrix least squares to residuals of 0.041, 0.047 for 1758, 1771 'observed' independent reflections respectively.
Abstract: Crystal structure determinations of (LH)2(B10H10), (1), and (LH2)(B10H10), (2), L = 2,2'- bipyridine , have been carried out by single-crystal X-ray diffraction methods at 295 K, being refined by full-matrix least squares to residuals of 0.041, 0.047 for 1758, 1771 'observed' independent reflections respectively. Crystals of (1) are monoclinic, P21/n, a 12.040(7), b 17.71(1), c 11.142(4) A, β 101.78(4)o, Z 4. Crystals of (2) are monoclinic, P21/c, a 9.937(4), b 10.837(3), c 14.856(5) A, β 109 2l(3)o, Z 4. The colour of the compounds is accounted for by charge-transfer interactions of a novel type, namely between the positively charged cationic acid hydrogen atoms and the negatively charged non-apical hydrogen atoms of the anion. In yellow (1), these distances are 2.26(5) A, while in red (2), they are much shorter, being 1.89(4), 1.97(3) A.
TL;DR: The equilibrium reactions between aluminium(III) and an epicatechin polymer or tannin (T) have been studied by potentiometric titration at 25oC, I = 0.001 M as mentioned in this paper.
Abstract: The equilibrium reactions between aluminium(III) and an epicatechin polymer or tannin (T) have been studied by potentiometric titration at 25oC, I = 0.001 M. The tannin, which has on average ten 1,2-dihydroxybenzene units per molecule, encapsulates the aluminium ion to form a bis(l,2-diphenolato) complex at pH 5-7. Stability constants are reported for Al(TH-2) (logK11-2, -3.95 ± 0.05), Al(TH-3) (logK11-3, -4.5 ± 0.1) and Al(TH-4) (logKl1-4, -5.7 ± 0.2). A small chelate effect arising from coordination of remote pairs of 1,2-diphenolato groups was observed.
TL;DR: A new Boesenbergia species was found to contain (+)-(1R,2S,3R,4S)-2-benzoyloxymethylcyclohex-5-ene-1,2,3,4-tetrol 4-benzoate [(+)- zeylenol ] (2) and the crotepoxide -related substance, (+)- (1R 2R, 4R, 5S, 6R, 7R)-4-benzinoyloxide-1-3,8-Dioxat
Abstract: A new Boesenbergia species ( Zingiberaceae ) has been found to contain (+)-(1R,2S,3R,4S)-2-benzoyloxymethylcyclohex-5-ene-1,2,3,4-tetrol 4-benzoate [(+)- zeylenol ] (2)and the crotepoxide -related substance, (+)-(1R,2R,4R,5S,6R,7R)-4-benzoyloxymethy1-3,8-Dioxatricyclo [5.1.0.02,4]octane-5,6-diol 5-acetate 6-benzoate ( boesenboxide ) (8). The structure (8) was determined by spectroscopic, chemical, and X-ray crystallographic studies. Boesenboxide forms monoclinic crystals P21, a 12.722(2), b 5.23O(l), c 16.139(3) A, β 106. 57(l)o; the crystal structure was refined to a residual of 0.029 for 1281 independent observed reflections.
TL;DR: In this paper, the title of Ph2P(CH2) was given and the mechanism of the cleavage reaction in liquid ammonia was discussed. But the mechanism was not discussed in detail.
Abstract: The title phosphines, Ph2P(CH2).PPh2 (n = 2-5), react with lithium in tetrahydrofuran to give the corresponding 1, n-dilithio-1, n-di(phenylphosphines) directly with little or no intermediacy of the 1-lithio- 1-phenyl- n- diphenylphosphinoalkanes which can, however, be obtained by arylation of the diphosphides. Methylenebisdiphenylphosphine and 1,4-diphenyl-1,4-diphosphinane undergo exclusive phosphorus-alkyl carbon cleavage. The chemistry and 31P n.m.r. spectroscopy of the diphosphides are described and the mechanism of the cleavage reaction is discussed. Some cleavage reactions in liquid ammonia are described.
TL;DR: In this article, the ligands Ph2PCH2PCh2P(Se)Ph2 ( dpmSe ) and Ph2AsCH2CH2PH2PSe (Ph2( apeSe ) have been treated with Group 6 metal pentacarbonyl halo anions, [M(C0)5X]-, the Group 6 hexacarbaronyls and the carbonyl halides M(C 0)4X2 (M = Mo, W, X = C1, Br).
Abstract: The ligands Ph2PCH2P(Se)Ph2 ( dpmSe ) and Ph2AsCH2CH2P(Se)Ph2 ( apeSe ) have been treated with Group 6 metal pentacarbonyl halo anions, [M(C0)5X]-, the Group 6 hexacarbonyls and the carbonyl halides M(C0)4X2 (M = Mo, W, X = C1, Br). Reaction of both dpmSe and apeSe with the anions [M(C0)5X]- in the presence of silver nitrate gave the complexes M(CO)5(L-L′) (L-L′ = dpmSe or apeSe ) with the ligand coordinated in a monodentate fashion through the Group 15 donor atom. Reaction of dpmSe with the hexacarbonyls gave only M(C0)4( dpmSe ) with the ligand chelated but, in contrast, apeSe could not be chelated to metal(0) and acted only as a monodentate ligand. These differences are rationalized in terms of the structure of the ligands. The behaviour of the ligands is much more similar in the metal(11) carbonyl halide chemistry. Both formed a mixture of two isomers of M(CO)3(L-L′)X2 (L-L′= dpmSe, apeSe ) in which the ligands are chelated . In the apeSe system, n.m.r. studies show these isomers are in an equilibrium which varies with temperature at a rate which is slow on the n.m.r. timescale, but the dpmSe complexes do not interchange. On reaction with further ligand, only one of the isomers of M(CO)3( dpmSe )X2 reacts to give incomplete formation of the dicarbonyl Mo(Co)2( dpmSe )2X2, which has one dpmSe ligand chelated and the other monodentate through phosphorus. On the other hand, for the apeSe system quantitative formation of Mo(CO)2( apeSe )2X2 was observed. For the apeSe system only, bubbling CO through a solution of M(CO)2( apeSe )2X2 gave M(CO)3( apeSe )2X2 with the ligands monodentate through arsenic. Extensive 31P and 77Se n.m.r. studies are described.