bluuebunny/crossref_metadata_2025 huggingface dataset:
Organolead(IV) Tricarboxylates, New Reagents for Organic Synthesis
Authors: Pinhey JT
Published: September 2010

Aryl-, vinyl- and alk-1-ynyl-lead(IV) tricarboxylates act as electrophilic arylating, vinylating and alkynylating agents, respectively, with a variety of nucleophiles, especially soft carbon nucleophiles such as β- dicarbonyl compounds, phenols and nitroalkanes. In their reactions, they show a marked preference for carbon-carbon bond formation, especially in which a quaternary centre is produced. The formation and the synthetically useful reactions of these new reagents are reviewed.
Alkyl and Alkenyl Resorcinols From an Australian Marine Sponge, Haliclona Sp (Haplosclerida : Haliclonidae)
Authors: Barrow RA , Capon RJ
Published: September 2010

Eleven alkyl and alkenyl resorcinols have been isolated from the Australian marine sponge Haliclona sp. Three of these, (3), (5) and (10), have previously been described from Australian terrestrial and marine plant sources. The remaining eight, (13)-(20), are new natural products whose structures have been secured by a combination of spectroscopic analysis and chemical degradation. This report represents the first account of this structure class being isolated from a non-plant source.
Rearrangements in the Furan Series. V. Reaction of 2,4-Di-p-methylanilino-cyclopent-2-enone With Maleic Anhydride
Authors: Darcy BR , Lewis KG , Oliver PJ , Mackay MF
Published: September 2010

A yellow product formed in the reaction of 2,4-di-p-methylanilinocyclopent-2-enone with maleic anhydride has been shown by X-ray crystallographic analysis to be (4′-p-methylanilino-1′-p-methylphenyl-2′,5′-dioxo-1′,2′,3′,5′,6′,6′a- hexahydrocyclopenta[b]pyrrol-3′-yl)acetic acid (3) in accord with the spectroscopic data. Monoclinic crystals of (3) belong to the space group P21/n with a 13.399(2), b 8.386(1), c 17.935(3)Ǻ, β 92.06(2)° and Z 4. Full-matrix refinement with 2292 observed data converged at R 0.063.
Constituents of Eupomatia Species. XII. Isolation of Constituents of the Tubers and Aerial Parts of Eupomatia bennettii and Determination of the Structures of New Alkaloids From the Aerial Parts of E. bennettii and Minor Alkaloids of E. laurina
Authors: Carroll AR , Taylor WC
Published: September 2010

Extraction of the aerial parts of Eupomatia bennettii F. Muell . yielded liriodenine, eupomatenoid-1, -3, -5 and -6, eupodienone-4 and -6, and the new compounds eupomatenoid-15 and -16, eupobennettin, eupomatilone-1, -2, -3, -4, -5 and -6, and four alkaloids imbiline-1, -2 and -3 and eupomatidine-1. From the tubers, eupomatenoid-1, -3, -4, -5 and -6, eupodienone-4 and -6 were isolated along with new products eupomatenoid-15, -16, -17 and -18, bennettinone and eupomatilone-3, -4, -6 and -7. Chemical and spectroscopic evidence is used to assign the structures of imbiline-1 (1), imbiline-2 (3), imbiline-3 (5) and eupomatidine-1 (6). The previously reported alkaloids from E. laurina R. Br., EL base-4 and EL base-5, were shown to be mixtures of imbiline-1, -2 and -3, and of eupomatidine-2 (10) and eupomatidine-3 (11), respectively. 3-Methoxyeupolauridine (15) was isolated from eupolauridine mother liquors.
The 4 Diepoxides of (R)-(+)-Limonene
Authors: Carman RM , Klika KD
Published: September 2010

The four diepoxides of limonene have been synthesized and separated, and their distinguishing spectral characteristics are described.
Reactions of Chelated β-Functionalized Amino Acids With Thionyl Chloride
Authors: Hartshorn RM , Sargeson AM
Published: September 2010

A variety of bis (ethane-1,2-diamine)cobalt(III) complexes containing chelated β-functionalized amino acids have been treated with SOCl2 in dimethylformamide. These compounds undergo β-elimination reactions to give chelated enamines followed by either rearrangement to the related imine complexes or further reactions with SOCl2 to give chelated isothiazole-3-carboxylato complexes. Mechanisms are proposed for the reactions.
Homogeneous Hydrogenation With Iridium Complexes. Evidence for Polyhydride Intermediates in the Reduction of α-Pinene
Authors: Brown JM , Derome AE , Hughes GD , Monaghan PK
Published: September 2010

The hydrogenation of α-pinene by Crabtree's catalyst [(cycloocta-1,5-diene)(pyridine)(tricyclo-hexylphosphine)iridium hexafluorophosphate] in dichloromethane, occurs from the endo -face with high stereospecificity. Reaction is accompanied by reversible equilibration with β-pinene, which forms 2% of the equilibrium mixture. The hydrogenation of β-pinene is slower than its isomerization under these conditions. Reductions were carried out with deuterium in order to probe the reaction mechanism. Using the novel technique of 2H-decoupled 13C n.m.r., it was found that a complete analysis of the isotope distribution in the product could be obtained by analysis of the C1 signal, since the possible β-and y-perturbations gave rise to distinct spectral shifts. All possible isotopomers corresponding to deuterium substitution at C2, C3 and C10 were observed, and no other site of deuteration was detected. Analysis of the product demonstrated that iridium polyhydrides are likely to be involved, since the results are inconsistent with simpler mechanistic pathways.
Synthesis Based on Cyclohexadienes. 5. A New Approach to the Synthesis of a-Ring Aromatic Steroids - a Formal Total Synthesis of (+/-)-Estrone
Authors: Rao GSRS , Banerjee DK , Devi LU , Sheriff U
Published: September 2010

A new strategy for the construction of A-ring aromatic steroids which resulted in the formal total synthesis of estrone is described. Thus reaction of the adduct (9), obtained from 1-methoxy-4-methylcyclohexa-1,4-diene and acrolein , with 3-(m-methoxypheny1) propyl -magnesium bromide followed by oxidation afforded the bicyclo [2.2.2] octene derivative (14). Acid-catalysed rearrangement of (14) followed by an intramolecular Michael addition resulted in the cis tetraenone (18) which was dehydrogenated with palladium chloride to the pentaenone (22). Li/NH3 reduction of (22) gave 3-methoxy-D-homoestra-1,3,5(10)-trien-16-one (31) which has been converted into the methyl ether (37) of marrianolic acid, and its methyl ester (38).
Multiple Carbon Bond Formation Via the Radical Cyclization of Cycloalkenol Acetals. Application to trans Hydrindan Steroid Precursors
Authors: Stork G , Franklin PJ
Published: September 2010

The cyclization of the α-iodo mixed acetals derived from properly substituted cyclohexenols , a process which has already been shown to permit the stereoselective and regioselective introduction of a different carbon chain at each of the termini of the allylic double bond, may be used for the construction of trans hydrindans suitable for further elaboration to steroids. In one particular instance, the process involves the formation of four new carbon-carbon bonds in a single operation.
Synthetic Anthracyclines From Anthraquinones
Authors: Cambie RC , Rutledge PS , Woodgate PD
Published: September 2010

Our syntheses of important and novel daunomycinones, aklavinones, fridarnycins and vineomycinones, from 1,4- or 1,5-dihydroxyanthraquinones, are reviewed. The reductive Claisen rearrangement has proven to be the most versatile of the methods developed for appending rings or functionalized side chains. Some novel polycyclic systems have been made, some interesting new properties of substituted quinizarins and anthrarufins uncovered, and new methods for elaboration of allyl systems developed.
Synthesis and Explosive Properties of Dinitropicrylbenzimidazoles, and the 'Trigger Linkage' in Dinitropicrylbenzotriazoles
Authors: Freyer AJ , Lowema CK , Nissan RA , Wilson WS
Published: September 2010

The synthesis of certain dinitropicrylbenzimidazoles and their structural elucidation are described. The explosive properties are discussed, and compared with those of the corresponding benzotriazoles. These comparisons allow the identification of the Pic-N-N=N moiety as containing the 'trigger linkage' for impact initiation of picrylbenzotriazoles.
The Stereochemistry of Organometallic Compounds. XXXVIII. Regio- and Stereo-control in the Rhodium-Catalyzed Hydroformylation of Some Alkenyl Phosphites
Authors: Jackson WR , Moffat MR , Perlmutter P , Tasdelen EE
Published: September 2010

Excellent regiocontrol is achieved in the rhodium-catalysed hydroformylation of some alkenyl phosphites, and good stereocontrol is obtained in the hydroformylation of some cyclohexenyl phosphites. The stereochemical results have implications for the mechanism of these rhodium-catalysed reactions.
Clemmensen Reduction. X. The Synthesis and Acidolysis of Some Aryl Alkyl Substituted Cyclopropane-1,2-diols
Authors: Davis BR , Hinds MG , Ting PPC
Published: September 2010

The synthesis of a number of 1-alkyl-2-arylcyclopropane-1,2-diols is reported. Reductive treatment of suitably substituted 1,3-diketones gave a cyclopropanediyl diacetate from which the diol was obtained. Reaction of these diols with acid gave α- hydroxy ketones , in which an alkyl group, rather than an aryl group, was adjacent to the carbonyl function. Clemmensen reduction of the 1,3-diketones gave products of rearrangement, generally similar to those obtained by acidolysis of the cyclopropane-1,2-diols. The relationship of these results to thermochemical studies on the stability of carboxonium ions is discussed.
Comparative Structural Studies on Three-Coordinate Copper(I) Halide Complexes With Tertiary Phosphines. Crystal Structures of [(PPh2Mes)CuX]2 and [(PPhMes2)CuX]2 (Mes = Mesityl X = Cl, Br, I)
Authors: Bowmaker GA , Camp D , Hart RD , Healy PC , Skelton BW , White AH
Published: September 2010

The 1 : 1 complexes of the substituted triphenylphosphine ligands mesityldiphenylphosphine
and dimesitylphenylphosphine with copper(1) chloride, bromide and iodide have been the
subject of single-crystal X-ray structure determinations at 295 K. All six complexes crystallize
as air-stable dimeric molecules, [(PPh2Mes)CuX]2 and [ (PPhMes2)CUX]2 with each copper
atom in a distorted trigonal PCuX2. coordination environment. Crystals of [(PPh2Mes)CuCl]2
(1) are monoclinic, P21/n, a 9.961(3), b 18.687(6), c 11.009(7) Ǻ, β 114.63(4)°; R was
0.049 for 2450 'observed' reflections. [(PPh2Mes)CuBrI2 (2) is monoclinic, P21/n, a 9.939(2),
b 18.832(6), c 11.238(6) Ǻ, β 115.36(3)°; R was 0.046 for 1803 'observed' reflections.
[(PPh2Mes)CuI]2.4/3 C6H6 (3) is rhornbohedral, R3, a 36.877(8), c 9.047(5) A; R was 0.039
for 2537 'observed' reflections. Crystals of [(PPhMes2)CuCl]2.2MeCN (4) are triclinic,
Pi, a 15.783(7), b 9.570(4), c 8.914(4) Ǻ, α 72.43(3), β 76.37(3), γ 74.03(3)°; R was
0.045 for 3341 'observed' reflections. [(PPhMes2)CuBr]2.3C6H6 (5) is monoclinic, C2/c, a
9.694(6), b 30.15(2), c 20.66(2) Ǻ, β 98.00(7)°; R was 0.047 for 2117 'observed' reflections.
[(PPhMes2)CuI]2.2MeCN (6) is orthorhombic, PP1nb, a 11.694(8), b 14.77(1), c 29.76(3) Ǻ;
R was 0.049 for 3447 'observed' reflections. Cu-P bond lengths are: 2.196(2) A (1); 2.198(3) Ǻ
(2); 2.222(5) and 2.226(5) Ǻ (3); 2.202(1) Ǻ (4); 2.197(3) A (5); 2.201(4) and 2.264(5) Ǻ
(6). The geometries of the LCuX2 and CuX2Cu units are compared with data reported for
other monomeric and dimeric compounds for both phosphorus- and nitrogen-based ligands L.
Pyrolytic Generation of Aryne and Exocyclic Carbene Species: Trapping by an Adjacent o-Tolyl Group
Authors: Brown RFC , Eastwood FW , Smith CJ
Published: September 2010

Flash vacuum pyrolysis of 2'-methylbiphenyl-2,3-dicarboxylic anhydride (3-o-tolylphthalic anhydride) at 860°/0.07mm gave a 1:1 mixture of 1H- and 3H-benz[e]indene (22%), and fluorene (49%). The pathways leading to these products are discussed.
A New Sesterterpene Tetronic Acid and a Pentaprenylated p-Quinol From an Australian Marine Sponge, Spongia sp.
Authors: Lumsdon D , Capon RJ , Thomas SG , Beveridge AA
Published: September 2010

The sesterterpene tetronic acid (1) and the pentaprenylated p- quinol (2) have been isolated from a specimen of sponge, Spongia sp., collected at a depth of 23 m from Port Phillip Bay, Australia. Structures were assigned on the basis of detailed spectroscopic analysis.
The Effects of Transition Metal Substitutions in the NbTe4-TaTe4 Charge-Density Wave System
Authors: Bennett JC , Boswell FW , Prodan A , Corbett JM , Ritchie S
Published: September 2010

At room temperature, the structures of TaTe4 and NbTe4 are modulated by the presence of a charge-density wave which in the former compound is commensurate with the parent lattice and in the latter incommensurate. In addition, a series of incommensurate mixed crystals ( Tal-xNbx )Te4 (0 ≤ x ≤) exist in which the modulation wavevector increases as a function of x. In this paper, we report the occurrence of a systematic variation in the period of the charge-density wave upon substitution of the transition metal elements Ti, Zr or V for either Nb or Ta. Electron diffraction experiments reveal that, in TaTe4, substitutions of Group 4 elements Ti and Zr result in an incommensurate modulation with a decrease in the modulation wavevector q. In NbTe4, substitutions of Ti or Zr also reduce q, in this case towards the commensurate value, and, at sufficiently high concentrations, a commensurate phase is stabilized at room temperature. Vanadium substitutions in NbTe4 result in a slight increase in q. Satellite dark-field images reveal the presence of defects in the modulation structures of the doped crystals. The above results are discussed in terms of the factors which determine the charge-density wave periodicity in the NbTe4-TaTe4 system.
A Transmission Electron Microscopy Study of the MnS-Er2S3 System
Authors: Landacanovas AR , Oterodiaz LC
Published: September 2010

A systematic search mainly by means of electron diffraction and microscopy techniques was performed to elucidate the structural behaviour of the Mn-Er-S ternary system at 1373-1773 K. At 1773 K a new phase MnEr2S4 with spinel structure, a = 11.97(2) � , was found. It transforms, due to electron beam damage (400 kV), into rock-salt (α-MnS ) domains and slabs of defects formed by some unit cells of MnEr2S4 (CaTi2O4 type) and MnEr4S7 (Y5S7 type) structures. The composition range between MnEr4S7 (S/M = 1.333) and MnEr4S7 (S/M = 1.400) is covered quasi-continuously by ordered and disordered intergrowth of both phases. Two ordered phases with composition Mn3Er8S15 (S/M = 1.3636) and Mn2Er6Sll (S/M = 1.375) have been found; however, disordered crystals due to a non-uniform mixing of those structures are more commonly observed. Furthermore, a new phase with a layer structure, reminiscent of LaCrS3 type, has been found mainly at 1373 K.
Can Thermal Vibration Amplitudes be Used as Indicators of Reaction Pathways? An Examination of [Nb, TaF7]2- Structures
Authors: Favas MC , Harrowfield JM , Kepert DL , Skelton BW , Vitolo LM , White AH
Published: September 2010

Thermal vibrational amplitudes, determined from a single-crystal X-ray study of K2TaF7 at room temperature, show similar characteristics to the neutron values for isomorphous K2NbF7, exhibiting considerable variations in anisotropies for the different fluorine atoms. These variations can be rationalized by using a combination of electron pair repulsion theory and crystal packing considerations.
Binding Constants for Cyclodextrin Inclusions by Competitive Spectrofluorometry Involving 6-(p-Toluidino)naphthalene-2-sulfonate
Authors: Johnson MD , Reinsborough VC
Published: September 2010

Binding constants of derivatized and simple β-cyclodextrins with a variety of inclusates were determined spectrofluorometrically through competition with 6-(p- toluidino )naphthalene- 2-sulfonate ( tns ). Inclusates in addition to tns were sodium alkane-1-sulfonates, sodium tetraphenylborate, sodium tetrafluoroborate, pyrazine and 4,4'-bipyridine.
Synthesis and Tubulin-Binding Properties of Some AC- and ABC-Ring Analogs of Allocolchicine
Authors: Banwell MG , Cameron JM , Corbett M , Dupuche JR , Hamel E , Lambert JN , Lin CM , Mackay MF
Published: September 2010

Fourteen analogues [compounds (8), (9) and (11)-(22)] of the powerful antimitotic agent allocolchicine (5) have been prepared and evaluated for their ability to prevent tubulin polymerization. The X-ray structure of one of the more active compounds, tricycle (20), is reported.
The Chemistry of 5-Oxodihydroisoxazoles. IV. Reactions of Some N-Arylisoxazol-5-ones With Nucleophiles
Authors: Ang KH , Donati C , Donkor A , Prager RH
Published: September 2010

The reactions of ethyl 2-aryl-5-oxo-2,5-dihydroisoxazole-4-carbolate (aryl = phenyl, isoquinolin-1-yl, 2-phenylquinazolin-4-yl and 5-nitropyridin-2-yl) with azide and primary, secondary and tertiary amines, and a number of other nucleophiles are described, and the product formation is rationalized in terms of predominant initial attack by the nucleophile at C3, or abstraction of H 3, of the isoxazole ring.
Synthesis of Pyrazino[2,3-c]isoquinolinecarboxylic Acids and Related Compounds
Authors: Deady LW , Quazi NH
Published: September 2010

1-Methylisoquinoline-3,4-diamine has been synthesized and condensed with α-dicarbonyl compounds to give the fused pyrazine ring. Oxidation of methyl groups gives the 3- and 6-carboxylic acids. Nitration occurs in the benzenoid ring to give the single 10-nitro product, and formation of an unusual 6-trinitromethyl compound is also reported.
Experiments Directed Towards the Synthesis of Anthracyclinones. XVII. Cyclization Reactions of Some Anthraquinone Conduritol Acetals
Authors: Cambie RC , Holroyd SE , Rutledge PS , Woodgate PD
Published: September 2010

Lewis acid induced intramolecular cyclization reactions of cyclohexenyl acetals derived from the condensation of the conduritol dimethyl ether (2) with the anthraquinone aldehyde (3) have been shown to give naphthacenediones as the only tetracyclic products.
Asymmetric\ Synthesis of Chiral Cyclic Amino Acids by Diels-Alder Reactions of (2S)- and (2R)-4-Methyleneoxazolidin-5-ones
Authors: Pyne SG , Dikic B , Gordon PA , Skelton BW , White AH
Published: September 2010

The synthesis of chiral (2S)- and (2R)-4-methyleneoxazolidin-5-ones, in high enantiomeric purity from (S)-S- methylcysteine, and their highly exo-selective Diels -Alder reactions with cyclic dienes are described. (1R,2S,4S)-2-Aminobicyclo[2.2.1]heptane-2-carboxylic acid has been prepared in 92% e.e. by these methods. A number of the products have been characterized by single-crystal X-ray methods, and their structure systematics examined.
The Structure and Synthesis of Some Minor Xanthones From the Lichen Rinodina thiomela
Authors: Elix JA , Gaul KL , Jiang H
Published: September 2010

The total synthesis of the xanthones 5,7-dichloro-8-hydroxy-2-methoxy-1,3-dimethyl-9H-xanthen-9-one(10),5,7-dichloro-2,8-dihydroxy-1,3-dimethyl-9H-xanthen-9-one(11),2-dechloro-8-O-methylthiomelin (6), 2-dechlorothiomelin (8), 4-dechloro-8-O-methylthiomelin (7), 4-dechlorothiomelin (5) and northiomelin (9) has been achieved. The compounds (5)-(7) and (10) were shown to be identical to the corresponding xanthones isolated from the lichen Rinodina thiomela, while chromatographic comparisons confirmed that the biosynthetically related xanthones (8), (9) and (11) were minor constituents of this species. This is the first reported natural occurrence of the xanthones (8) and (11).
Dihydroxylation of 1,7-Dioxaspiro[5.5]undec-4-enes
Authors: Brimble MA , Nairn MR
Published: September 2010

The highly stereoselective syn-hydroxylation of the unsaturated spiro acetals (4-8) with osmium tetraoxide is reported. In all cases, hydroxylation occurred from the β-face giving the diols in which the hydroxy group at C5 is axial and anti to the C-O bond of the neighbouring tetrahydropyran ring.
Diiodo Acetals and Unsaturated Lactones From Dihydropyran
Authors: Lynch MJ , Simpson J , Weavers RT
Published: September 2010

Reaction of dihydropyran with propiolic acid and N- iodosuccinimide gave an iodo ester which was cyclized under free-radical conditions to form an (E) iodomethylene lactone. Photolysis of this lactone could be controlled to generate mixtures of (E) and (Z) iodomethylene lactones, or alternatively the iodine-free methylene lactone. The structures of some by-products of the iodo ester formation have been shown to be a succinimide derivative and two stereoisomers of a diiodo acetal. X-Ray determination of the structure of one of the diiodo acetal isomers is described.
Two Sulfur-Containing Isoquinoline Alkaloids From the Bryozoan Biflustra perfragilis
Authors: Blackman AJ , Ralph CE , Skelton BW , White AH
Published: September 2010

The bryozoan Biflustra perfragilis collected in Bass Strait has yielded two novel sulfur-containing isoquinoline alkaloids: 2-methyl-6,7-di(methylthio)isoquinoline-3,5,8 (2H)-trione (1a) and 2-methyl-6-methylthioisoquinoline-3,5,8(2H)trione (1b). A single-crystal X-ray study supports the assignment of (1a).
Synthesis and Characterization of Triammine-triaquaruthenium(III) Trifluoromethanesulfonate
Authors: Diamantis AA , Moritz PS
Published: September 2010

[ Ru (NH3)3(OH2)3](CF3SO3)3 was prepared from RuCl3(NH3)3 by using trifluoromethanesulfonic acid and Ag2CO3, and characterized by microanalytical , electrochemical and spectroscopic techniques. The complex is soluble in water and in many organic solvents and is a convenient starting material for the preparation of triammine complexes. [RU(NH3)3(OH2)3]3+ has pKa1 3.77�0.04 and pKa2 6.93�0.04 at 25°C, and an E½ of -120 mV at pH 1.5 and -190 mV at pH 5. In the u.v . spectrum λmax is at 251 nm (є 1150 mol-1 dm3 cm-1) in 0.1 M H+ and at 296 nm (є 1760 mol-1 dm3 cm-1) at pH 5. [ Ru (NH3)4(OH2)2]3+ has pKa1 3.96�0.4 and pKa2 7.09�0.04 and E1/2 of -140mV at pH 1 and -200mV at pH 5. In the u.v. spectrum λmax is at 254 nm (є 1200 mol-1 dm3 cm-1) in 0.1 M H+ and at 296 nm (є 2650 mol-1 dm3 cm-1) at pH 5. [ Ru (NH3)3(OH2)3]2+ can be prepared in situ by reduction with Zn(Hg) or H2/Pt black; at high pH, the reduction proceeds via a blue mixed-oxidation-state intermediate.
The Synthesis of a Series of 5-Ethenyl γ-Lactones
Authors: Perlmutter P , Mccarthy TD
Published: September 2010

The synthesis of 5-ethenyl γ-lactones is readily achieved in three steps from 3-methoxycarbonyl-propionyl chloride by using the Baylis-Hillman coupling reaction as a key step.
Self-Association of Nicotinamide in Aqueous-Solution: N.M.R. Studies of Nicotinamide and the Mono- and Di-methyl-Substituted Amide Analogs
Authors: Charman WN , Lai CSC , Craik DJ , Finnin BC , Reed BL
Published: September 2010

The concentration-dependent self-association of nicotinamide in solution has been studied by 1H and 13C n.m.r. spectroscopy, attendant relaxation time measurements, and osmometric techniques. N-Methylnicotinamide and N,N- dimethylnicotinamide were also studied to evaluate the role of the amide group in the association process. The osmometric studies indicated that the dimethyl -substituted analogue underwent little (if any) self-association, whereas nicotinamide and N- methylnicotinamide did self-associate. The concentration-dependent 1H and 13C chemical shift profiles of nicotinamide and the monosubstituted analogue indicated that the association involved the amide group and did not occur through stacking of the pyridine rings. Spin lattice relaxation (T1) studies indicated that the T1( ortho C)/T1( para C) ratio of nicotinamide decreased with increasing concentration, and that loss of a preferred axis of rotation had occurred due to formation of a large associated species. The T1 ratios of either substituted amide analogue were not concentration-dependent. The extent of self-association of the monosubstituted derivative was insufficient to affect the measured T1 ratios. These data indicate that the self-association of nicotinamide in aqueous solution occurs primarily through interamide hydrogen bonding.
Chemistry of Some [1,2,5]Oxadiazolo[3,4-c]isoquinolines and N-Oxides
Authors: Deady LW , Quazi NH
Published: September 2010

The reaction of some 4-nitroisoquinolin-3-amines with iodosobenzene diacetate [ PhI ( OAc )2] is a convenient preparation of the title compound N-oxides. Attempts to convert these into quinoxaline N,N′-dioxides were not successful, but reactions of some 5-substituents are described, along with deoxygenation to the corresponding furazan derivatives.
A Caveat Concerning the Use of the AM1 and PM3 Semiempirical Methods in Calculating Conformational Preferences in Acyclic Amines and Saturated Azaheterocycles
Authors: Shephard MJ , Paddonrow MN
Published: September 2010

A theoretical investigation of the conformational analysis of several acyclic amines, N- alkylated saturated azaheterocycles and alkylcyclohexanes (alkyl = Me, Et, isopropyl, t-butyl) has been carried out by using the MNDO, AM1 and PM3 semiempirical methods. It is found that all three methods correctly predict, qualitatively, the conformational preferences in alkylcyclohexanes, although the PM3 method underestimates the conformational energy for the t-butyl group by as much as 13 kJ/mol. Both AM1 and PM3 overestimate the conformational energy of the nitrogen lone pair to the extent that it exceeds that of the isopropyl group and (in the case of PM3) the t-butyl group, thereby leading to erroneous predictions of favoured conformations in amines and azaheterocycles . Thus, axial N-alkylpiperidines are predicted to be more stable than the equatorial conformers. Thus, application of the AM1 and PM3 methods to the conformational analysis of molecules containing amine functionalities is not recommended. Although the MNDO method gives a qualitative account of the conformational analysis of such molecules, with the exception of hexahydropyridazines and hexahydropyrimidines, the resulting conformational energies and molecular geometries are in poor agreement with experimental data.
Synthesis of New Arylsulfonylurea Derivatives of Saccharin
Authors: Benicha M , Azmani A , Akssira M , Hurst DT
Published: September 2010

Some new sulfonylurea derivatives (2a-j) of saccharin have been obtained by the reaction of ethyl 3-oxo-1,2-benzisothiazole-2(3H)-carboxylate 1,1-dioxide (1) with the appropriate amine. Ethyl 3-oxo-1,2-benzisothiazole-2(3H)-carboxylate 1,1-dioxide was obtained, in excellent yield, by the reaction of ethyl chloroformate with saccharin.
Powder Neutron Diffraction Study of Pyrolusite, β-MnO2
Authors: Bolzan AA , Fong C , Kennedy BJ , Howard CJ
Published: September 2010

The powder neutron diffraction pattern of pyrolusite, β-MnO2 [P42/mnm, No. 136, a = 4.4041(1), c = 2.8765(1)Ǻ], has been refined by the Rietveld method to give values for both the oxygen position parameter u=0.3046(1) and the anisotropic thermal parameters. The data confirm the MnO6 octahedra to be elongated with two long [1.894(1)Ǻ] and four short [1.882(2)Ǻ] Mn-O bond distances. The effect of the stereochemistry on the thermal vibrations is discussed.
Synthesis of 2β-Hydroxyursolic Acid and Other Ursane Analogs From Ursonic Acid
Authors: Begum S , Adil Q , Siddiqui BS , Siddiqui S
Published: September 2010

Synthesis of the natural product 2β-hydroxyursolic acid (6) has been achieved through reaction of ursonic acid (1) with SeO2, and subsequent stereospecific reduction of the 2,3-diketo derivative (3) and its tautomer diosphenol (4), with NaBH4 under mild reaction conditions. Several other analogues (2), (5), (7) and (8) of the ursane series have also been obtained during these reactions.
The Chemistry of Laurenene. XVI. Investigation of the Mechanism of a Cationic Rearrangement
Authors: Clarke DB , Weavers RT
Published: September 2010

Some aspects of the mechanism of the acid-induced rearrangement of laurenan-2β-ol have been deduced from deuterium- labelling studies. A key intermediate arises from two pathways, one involving a 1,4- and one a 1,5-hydride shift. Formation of this intermediate is partially suppressed by substitution of the migrating hydrogen by a deuterium. A proposed pathway which involves a 1,3-methyl migration has been disproved, and scrambling and loss of deuterium label has been accounted for in terms of equilibria involving lauren-1-ene and another previously reported rearrangement product. The rearrangement is strongly promoted in dichloromethane, and the product composition is highly solvent-dependent.
New Imidazole Alkaloids From the Sponge Leucetta sp. and the Associated Predatory Nudibranch Notodoris gardineri
Authors: Carroll AR , Bowden BF , Coll JC
Published: September 2010

Three new imidazole alkaloids, naamidines Eand F and clathridine C, have been isolated from a sponge Leucetta sp., together with the known imidazole alkaloids naamidine A, pyronaamidine, clathridine and kealiiquinone. The predatory nudibranch Notodoris gardineri, which was found feeding on the sponge, contained the known metabolite clathridine. The structures of all compounds were delineated on the basis of one-dimensional and two-dimensional n.m.r. experiments at 300 MHz.
Beyond Polygodial: New Drimane Sesquiterpenes From a Southern Australian Marine Sponge, Dysidea sp.
Authors: Butler MS , Capon RJ
Published: September 2010

This report describes the isolation and structure elucidation of four new drimane sesquiterpenes (14)-(17) from a southern Australian marine sponge Dysidea sp. The structures for (14)-(17) were secured by detailed spectroscopic analysis, chemical interconversion and derivatization. Also reported are the known metabolites (+)- euryfuran (7), dihydropallescensin-2 (18), (-)- pallescensin-A (19) and (-)-7-deacetoxyolepupane (6). The rare co-occurrence of two antipodes, (7) and (19), in the same specimen highlights the dangers in assigning absolute stereochemistry based on 'unproven' biosynthetic relationships. The absolute stereochemistry for (6) has been unambiguously established for the first time by chemical interconversion to (7). Furthermore, the absolute stereochemistry of the new marine metabolites listed above, (14)-(17), were determined by chemical correlation to (6). A biosynthetic and ecological relationship is proposed between the metabolites from Dysidea sp. with the known marine and terrestrial antifeedant polygodial (8). Chemical investigations are reported that support this proposition.
Isopalinurin: a Mild Protein Phosphatase Inhibitor From a Southern Australian Marine Sponge, Dysidea sp.
Authors: Murray L , Sim ATR , Rostas JAP , Capon RJ
Published: September 2010

A new sesterterpene tetronic acid, isopalinurin (1), has been isolated from an Australian marine sponge, Dysidea sp., collected in Bass Strait. Isopalinurin (1) was identified as the agent responsible for the antibiotic activity and protein phosphatase inhibitory properties exhibited by the crude ethanol extract, and its structure was secured by detailed spectroscopic analysis.
A Pyrolytic Preparation of (S)-2-(t-Butyl-Dimethyl-silyloxymethyl)-2,3-dihydrofuran
Authors: Brown RFC , Mcgeary RP
Published: September 2010

The silyl-protected dihydrofuran (4) is readily prepared in 92% yield by flash vacuum pyrolysis of the 2-acetoxytetrahydrofuran derivative (8).
Water Molecule Dispositions in the Cesium Sulfate α- and β-Alums: Single-Crystal Neutron Diffraction Studies of CsM(SO4)2.12H2O (M=V, Rh)
Authors: Beattie JK , Best SP , Moore FH , Skelton BW , White AH
Published: September 2010

Room-temperature single-crystal neutron diffraction studies are recorded for two alums, Cs( Rh /V)(SO4)2.12H2O [cubic, Pa3, a 12.357(5) ( Rh ), 12.434(1)Ǻ (V)], residuals 0.037 and 0.068 for 328 and 164 'observed' reflections, with the intention of defining water molecule hydrogen atom orientations. Whereas the two tervalent hexaaqua cations are similar in size [ rM -O = 2.010(6)Ǻ (M = V) and 2.006(2)Ǻ (M = Rh )] the vanadium salt adopts the β alum modification while rhodium gives an α alum. Significantly, the water coordination geometry is different in the two cases with the tilt angle between the plane of the water molecule and the M-O bond vector being 1° (M = V) and 35° (M = Rh ). The tilt angle for water coordinated to rhodium in CsRh (SeO4)2.12H2O is inferred from the unit cell dimensions to be similar to that of the corresponding sulfate salt and not that which generally pertains for caesium selenate alums. Significant differences in the H-O-H bond angle are found for trigonal planar and trigonal pyramidal water coordination, suggesting that differences in the metal(III)-water interaction are a determinant of the geometry of the coordinated water molecule in the caesium sulfate/ selenate alum lattices.
Reaction of 3-Methylenecholest-5-ene With Singlet Oxygen: Peroxyl Radical Cyclization Competitive With Allylic Rearrangement
Authors: Schiesser CH , Wu H
Published: September 2010

3-Methylenecholest-5-ene reacts with singlet oxygen to give 5α-hydroperoxy-3-methylenecholest-6-ene which, in turn, rearranges rapidly to 3β-hydroperoxy-5α,3α-( epidioxymethano )cholest-6-ene by free-radical cyclization , and 7α-hydroperoxy-3-methylenecholest-5-ene by allylic rearrangement.
The E.S.R. Spectra of Some Radical Cations Derived From Aryl Ethers and Quinones
Authors: Hewgill FR , Legge F , Webb RJ
Published: September 2010

Radical cations were generated by oxidation of various highly substituted aryl methyl ethers with thallium(III) or lead(IV). Diprotonated radical cations of quinones with strongly electron-donating substituents were produced merely on solution in trifluoroacetic or methanesulfonic acids.
Nitrones and Oxaziridines. LXVII. Intermolecular Cycloaddition of Fused Indolyl Nitrone Ring Systems
Authors: Black DSC , Craig DC , Debdas RB , Kumar N , Wright TA
Published: September 2010

The two dihydro-β-carboline N-oxides (6) and (18) have been prepared by reductive cyclization of 2-acetyl-3-(β- nitroethyl ) indoles. These cyclic nitrones undergo 1,3-dipolar cycloaddition to alkynes to give the cycloadducts (21)-(25). Thermal rearrangement of the adduct (22) gives the indolizino [8,7-b] indole (27) in high yield. The X-ray crystal structure determination of the adduct (24) is reported.
Mechanism of Oxidative Dehydrogenation of an Amine Coordinated to Osmium(II)
Authors: Keene FR , Lay PA , Sneddon GE , Whebell GW
Published: September 2010

The synthesis and characterization of [Os( bpy )2( ampy )]2+{ bpy = 2,2′-bipyridine; ampy = 2-( aminomethyl )pyridine} have been studied, together with its irreversible two-electron oxidative dehydrogenation to the corresponding osmium(II) imine species in aqueous solution, by utilizing electrochemical and stopped-flow kinetic techniques. The kinetic data were analysed by using numerical integration methods to obtain solutions for the differential equations derived from mechanistic proposals. The results were consistent with the initial oxidation of the metal centre to OsIII and the intermediacy of a deprotonated OsIV species, formed by disproportionation, in the subsequent ligand dehydrogenation.
The Photochemical Generation of Isoindene and Its Dimerization to Diastereomeric 1-(Indian-1-yl)indenes
Authors: Warrener RN , Pitt IG , Russell RA
Published: September 2010

Isoindene (1), generated by ultraviolet irradiation ( Vycor filter, acetone solution) of 1,4- dihydro-1,4-methanonaphthalene-2,3-dione (14), is shown to undergo homodimerization at -60°. This cycloaddition involves the intermolecular transfer of a hydrogen atom from one isoindene molecule to a second isoindene molecule in an [(8π+2σ)+ Sπ ] pericyclic process. The gross structure of the resulting diastereomeric dimers was confirmed by synthesis from 1-bromoindan (25) and indenyl anion (26). The stereochemistry of the dimers was determined by comparing their dihydro derivatives (33) and (34) with authentic samples. The authentic samples were themselves prepared by cis hydrogenation (Pd/C) of (E)-2,2′,3,3′-tetrahydro-1,1′-bi-1H-indenylidene (30) which yielded (34), and trans hydrogenation (Na/NH3) of (30) which formed (33) together with (34) (ratio 7:3). The (E) stereochemistry of (30), which was a critical feature in the stereochemical assignments to (33) and (34), was confirmed by n.O.e. studies on it and its (D4)derivative (32). Complete analysis of the proton, proton coupling was conducted on (32). This identified a 5J coupling between protons C 3-H and C 7-H which contributed a 6% scalar coupling to the observed n.O.e . of 39% at C 7-H. This information allowed unambiguous stereochemical assignments to be made to (33). The chirality of 1,1′-bi-1H-indenyls (43) and (44), prepared by the radical coupling of 1H-inden-1-ylmagnesium bromide, was also determined by a similar hydrogenation process.
The Meisenheimer Rearrangement in Heterocyclic Synthesis. V. A Derivative of Each of the 3,7-Epoxy-3-benzazonine and 2h-3,8-Epoxy-3-benzazecine Systems
Authors: Bailey TS , Bremner JB
Published: September 2010

Meisenheimer rearrangement of the 10b-vinylpyrrolo[2,1-a] isoquinoline and 11b-vinylbenzo[a]- quinolizine N-oxide derivatives (4a,b) gave, in low yield, the first examples of the 3,7-epoxy- 3-benzazonine and 2H-3,8-epoxy-3-benzazecine ring systems (5a) and (5b) respectively.
Complexation of Alkali Metal Ions by the Cryptand 4,7,13,16-Tetraoxa-1,10-diazabicyclo[8.8.5]tricosane in Several Solvents
Authors: Dhillon R , Lincoln SF
Published: September 2010

A potentiometric titration study of the complexation of metal ions (M+) by 4,7,13,16- tetraoxa-1,10-diazabicyclo[8.8.5] tricosane (C22C5) at 298.2 K and I = 0.05 (NEt4ClO4) yields log(K/dm3 mol-1) =6.07 and 5.36, 7.55 and 5.95, 6.26 and 7.56, 5.5 and 6.66, 4.57 and 5.16, and 8.14 and 14.51 when M+ = Li+, Na+, K+, Rb +, Cs+ and Ag+, respectively, where the first and second magnitudes of each pair refer to the stability constant (K) for [M(C22C5)]+ in acetonitrile and ropylene carbonate solvent, respectively. A 7Li n.m.r. tudy yields kd (298.2 K) = 428 s-1, ∆ Hd ‡ = 24.7 kJ mol-1 and ∆ Sd ‡ = -111 J K-1 mol-1 for the monomolecular decomplexation of Li+ from [Li(C22C5)]+, and kc(298.2 K) = 9.83×107 dm3 mol-1 s-1 for the complexation process in propylene carbonate. These data are compared with those for related systems and are discussed in terms of the factors affecting cryptate stability and lability.
Cooperative Spin Transitions in Iron(II) Derivatives of 1,2,4-Triazole
Authors: Sugiyarto KH , Goodwin HA
Published: September 2010

Complexes of stoichiometry Fe( trzH )2( trz )X, where trzH is 1,2,4-triazole and X = BF4, ClO4, PF6, have been prepared. All three salts display temperature-induced singlet (1A1) ↔ quintet (5T2) transitions which are generally discontinuous and associated with a broad hysteresis loop. The salts are strongly thermochromic, being white above and pink-lilac below the transition region. Several samples of each salt were obtained and the detailed behaviour varied somewhat from one sample to another. For the fluoroborate and perchlorate salts the transition is centred above room temperature while for the hexafluorophosphate salt it occurs below room temperature. The perchlorate salt was also isolated in a form which showed a continuous transition but the nature of its electronic properties changed as the sample aged. In one form of the hexafluorophosphate salt the hysteresis loop spans room temperature and it has been possible to characterize both the singlet and the quintet state species at that temperature. For all three salts the transition has been characterized by measurement of the temperature dependence of the magnetism and Mossbauer and electronic spectra. These measurements establish that the complexes all contain an FeN6 coordination core and this must be achieved through bridging of the triazole units.
Pyrolytic Generation of 3-Phenylindol-2-ylmethylene-carbene and Its Cyclization to 7H-Benzo[c]carbazole
Authors: Brown RFC , Coulston KJ , Eastwood FW , Manyweathers JJ
Published: September 2010

Flash vacuum pyrolysis of the 3-phenylindol-2-ylmethylene derivative (12) of Meldrum's acid at 600° and at 750°/0.03 mm gives 9-phenyl-3H-pyrrolo[1,2-a]indol-3-one (14) (97%). At 900°/0.3 mm (14) (49%) is accompanied by 7H-benzo[c] carbazole (6) (10%). The latter is formed by intramolecular C-H insertion in the title carbene (5).
Intramolecular Condensation Reactions of S-Methylmethionine Coordinated to Cobalt(III)
Authors: Angus PM , Golding BT , Jurisson SS , Sargeson AM , Willis AC
Published: September 2010

The sulfonium salt [(en)2CoO2CCH(NH2)(CH2)2S(CH3)2]3+ (en = ethane-1,2-diamine), prepared by methylation of the thioether group of N,O-coordinated methionine , undergoes a set of complex, intramolecular condensations, oxidations, and rearrangements in aqueous base to give a novel pentadentate cobalt(III) complex (c. 20%) of the 1,9-diamino-4-hydroxy-3,7-diazanonane-4-carboxylate ion ( dhnc ). Its structure has been determined by X-ray crystallographic analysis as trans(O,O)-[Co( dhnc )(OH2)](ClO4)2.2H2O. The crystals were monoclinic, space group P 21/c with a 9.053(2), b 29.437(7), c 7.661(1) Ǻ, β 106.63(1)°, and Z 4; 2383 data with I ≥ 3σ(I) were refined to conventional R factors of 0.046 and 0.060. Investigations concerning the mechanism for the formation of this complex are described.
Synthesis of 1,8,8-Trimethyl-6,10-dioxaspiro[4.5]dec-2-ene-1-ethanol; X-Ray Crystallography of (1RS,2SR)-1,8,8-Trimethyl-1-(prop-2'-enyl)-6,10-dioxaspiro[4.5]dec-2-yl Benzoate
Authors: Collins DJ , Fallon GD , Mcgeary RP
Published: September 2010

Reaction of 2-methyl-2-(prop-2′-enyl)cyclopentane-1,3-dione (2) with 2,2-dimethylpropane-1,3-diol gave 1,8,8-trimethyl-1-(prop-2′-enyl)-6,10-dioxaspiro[4.5]decan-2-one (3), hydride reduction of which afforded a 1:1 epimeric mixture of the corresponding alcohols (4a) and (4b). They were separated, and the derived benzoates (5a) and (5b) were each subjected to a three-step sequence of oxidative cleavage, borohydride reduction and silylation to give the pure epimers (8a) and (8b) of 1,8,8-trimethyl-1-(2′-t-butyldimethylsilyloxyethyl)-6,10-dioxaspiro[4.5]dec-2-yl benzoate. Flash vacuum pyrolysis of a mixture of these epimeric benzoates (8a,b) gave an almost quantitative yield of 1,8,8-trimethyl-1-(2′-t-butyldimethylsilyloxyethyl)-6,10-dioxaspiro[4.5]dec-2-ene (9a), treatment of which with tetrabutylammonium fluoride afforded the corresponding alcohol (9b). The relative stereochemistry of (1RS,2SR)-1,8,8-trimethyl-1-(prop-2′-enyl)-6,10-dioxaspiro [4.5]dec-2-yl benzoate (5b) was established by X-ray crystallography.
Structural and Electronic Properties of Bis[2-(pyrazin-2-ylamino)-4-(pyridin-2-yl)thiazolato]iron(II) and Its Solvated Derivatives
Authors: Childs BJ , Craig DC , Ross KA , Scudder ML , Goodwin HA
Published: September 2010

The uncharged complex [Fe( pzapt )2] [ pzapt is the deprotonated form of 2-(pyrazin-2-ylamino)-4-(pyridin-2-yl) thiazole ] crystallizes with varying degrees of solvation , depending on the solvent. The electronic properties of the solvates differ. For all of them temperature dependence of the magnetic moment is observed, associated with a continuous temperature-induced singlet (1A1) ↔ quintet (5T2) transition. The transition is centred below room temperature for the benzene solvates but the unsolvated and chloroform solvate complexes exist predominantly in a singlet low-spin state. Overall the stabilization of the singlet state is greater in this system than in the previously studied [Fe( papt )2] [ paptH = 2-(pyridin-2-ylamino)-4-(pyridin-2-yl) thiazole ]. A spin equilibrium has been characterized for both [Fe( pzapt )2] and [Fe( papt )2] in methanol solution. The crystal structure of [Fe( pzapt )2].3/2C6H6 reveals Fe-N bond lengths consistent with both singlet and quintet state iron(II) being present. The benzene molecules are incorporated into the lattice as groups of three by occupying channels created by the packing of the complex molecules. Bis [2-(pyrazin-2-ylamino)-4-(pyridin-2-yl) thiazole ]iron(II) sesquibenzene solvate: monoclinic, space group P 21/c, a 14.894(7), b 12.601(2), c 16.777(8) Ǻ, β 94.57(2)°, Z 4.
Intramolecular Oxidative Coupling of Aromatic Compounds. VI. An Efficient Synthesis of Some Dibenzocyclooctene Lignans
Authors: Carroll AR , Taylor WC
Published: September 2010

The 1,4-diaryl-2,3-dimethylbutanes (4) and (5) were readily prepared by reductive coupling of an arylacetone precursor followed by hydrogenation. Intramolecular oxidative coupling (dichlorodicyanobenzoquinone/trifluoroacetic acid) gave dibenzocyclooctene derivatives in good yield. (�)-Deoxyschizandrin and the corresponding trans isomer, existing in two distinct conformations, were prepared.
Marine Sesquiterpene Quinones and Hydroquinones: Acid-Catalyzed Rearrangements and Stereochemical Investigations
Authors: Urban S , Capon RJ
Published: September 2010

Acid treatment of both ilimaquinone (3) and 5-epi-ilimaquinone (9) yielded the same rearrangement products, (7) and (8), thus defining a common absolute stereochemistry. Likewise, acid- catalysed rearrangement of avarol (10) and arenarol (11) yielded the common product aureol (13), allowing the absolute stereochemistry of arenarol (11) and its related quinone arenarone (12) to be assigned. This latter acid- catalysed rearrangement also yielded an unexpected electrophilic aromatic cyclization product (15), the dimethyl ether (17) of which could be obtained in quantitative yield from acid treatment of avarol dimethyl ether (16).
The Crystal Structure of Silver(I) Glycolate Hemihydrate
Authors: Smith G , Reddy AN , Byriel KA , Kennard CHL
Published: September 2010

The silver(I) complex with glycolic acid, [Ag2(HOCH2CO2)2]n.nH2O,
has been prepared and its structure determined by X-ray diffraction. The structure is based on a bis(carboxylato-O,O′) dimer [Ag-O, 2.234(2), 2.253(2) Ǻ; Ag-Ag 2.8810(9)Ǻ], extended in both the axial positions into a network polymer through two oxygens of a bidentate α-hydroxy carboxy residue [Ag-O(hydroxy), 2.607(2) Ǻ; Ag-O(carboxy), 2.456(2)Ǻ; O-Ag-O, 63.45(5)′]. In this respect, the complex is unique among silver(I) carboxylate dimers.
New Depsides From the Lichen Lecanora planaica
Authors: Elix JA , Elix JA , Barclay CE , Barclay CE , Lumbsch HT , Lumbsch HT
Published: September 2010

The new depsides hyperplanaic acid (4), isohyperplanaic acid (5) and superplanaic acid (6) have been detected in the lichen Lecanora planaica and the structure of these metabolites has been established by unambiguous synthesis.
Photochemical Nitration by Tetranitromethane .XVI. The Regiochemistry of Adduct Formation in the Photochemical Reaction of 1,8-Dimethylnaphthalene and Tetranitromethane; Thermal 1,3-Dipolar Nitro Addition Reactions
Authors: Calvert JL , Eberson L , Hartshorn MP , Maclaga n , Robinson WT
Published: September 2010

Photolysis of the 1,8-dimethylnaphthalene/tetranitromethane charge-transfer complex yields the triad of 1,8-dimethylnaphthalene radical cation, nitrogen dioxide, and trinitromethanide ion. In dichloromethane at +20° recombination of this triad gives predominantly the adducts (8), (9), (11), and (14), each of which is formed by attack of the trinitromethanide ion at C4 of the 1,8-dimethylnaphthalene radical cation; a minor adduct (10) is formed by similar attack but at C3 of the aromatic radical cation. The cycloadducts (12) and (13) arise by cycloaddition of the trinitromethyl group to the alkene function in adducts (9) and (14). The cycloaddition (9)→(12) has been shown to be a thermal, not photochemical, reaction. X-Ray crystal structures are reported for adducts (8) and (12).
Organoamido- and Aryloxo-lanthanoids. X. Tris(η2-3,5-di-t-butylpyrazolato)lanthanoid(III) Complexes and the X-Ray Crystal Structure of Er(η2-But2pz)3(thf)2
Authors: Cosgriff JE , Deacon GB , Gatehouse BM , Hemling H , Schumann H
Published: September 2010

The complexes Ln (But2pz)3( thf )2 ( Ln = Y, La, Pr, Nd , Sm, Gd, Dy , Er , Yb, Lu; But2pz- = 3,5-di-t-butylpyrazolate; thf = tetrahydrofuran ), and [ Ln (But2pz)3(OPPh3)2].( dme )n ( Ln = La, n = ⅔ ; Ln = Er , n = 1; dme = 1,2-dimethoxyethane) have been prepared by reaction of the lanthanoid metal with bis ( pentafluorophenyl )mercury and the corresponding pyrazole in either thf , or in dme in the presence of triphenylphosphine oxide. The X-ray crystal structure of Er (η2-But2pz)3( thf )2 [monoclinic, space group P21 (No. 4), a 9.738(4), b 19.602(4), c 11.636(4) Ǻ, β 99.42(3)°, R 0.0374 for 3667 observed reflections] shows the complex to be an eight-coordinate monomer with three chelating But2pz ligands . The arrangement of centres ( Cen ) of the N-N bonds of the But2pz ligands [< Er -N> 2.336 Ǻ; Cen-Er-Cen 140.1(4)°, 110.3(4)° and 109.6(4)°] and the thf oxygen atoms [< Er -O> 2.351 Ǻ; O- Er -O 140.1(4)°] is intermediate between trigonal bipyramidal and square pyramidal. The other Ln (But2pz)3( thf )2 complexes and Ln (But2pz)3(OPPh3)2 are considered to have similar structures.