摘要:

Treatment of ethyl 2-pentynoate (14) with lithium (phenylthio)(tri-n-butylstannyl)cuprate (12) afforded, in 76% yield, ethyl (Z)-3-(tri-n-butylstannyl)-2-pentenoate (15). On the other hand, when compound14was allowed to react with the (tri-n-butylstannyl)copper reagent13, ethyl (E)-3-(tri-n-butylstannyl)-2-pentenoate (21) was produced in 83% yield. Reduction (diisobutylaluminum hydride, ether) of the esters15and21gave the alcohols16and22, respectively. Treatment of each of the latter substances with pyridine – sulfur trioxide complex, followed by further reduction of the resultant intermediates with lithium aluminum hydride, provided the geometrically isomeric alkenylstannanes17and23. Conjugate addition of (E)-3-lithio-2-pentene (18) (formed by transmetalation of17) to compound19produced the olefinic trimethylhydrazide20, which was converted (diisobutylaluminum hydride, ether; pyridinium dichromate, dimethylformamide) into the corresponding carboxylic acid2. Subjection of compound23to a sequence of reactions identical with that used for the conversion of17into2provided the isomeric acid3, which was identical (infrared,1H nmr) with the natural acid derived from triophamine (1). Conversion of3into thep-nitrophenyl ester26, followed by condensation of the latter substance with guanidine, afforded a chromatographically separable mixture of (±)-triophamine (1) and the corresponding diastereomer.

ISSN:0008-4042    

DOI:10.1139/v84-001

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

N,N-Dimethyl ethanolamineN-oxide (DMEAO) belongs to the class of tertiary amine oxide molecules that are good solvents for cellulose, although not being cyclic. Crystallographic investigation shows that anhydrous DMEAO is monoclinic, space groupCc,a = 25.725(9),b = 7.023(4),c = 9.483(5) Å, β = 101.16(10)°,Z = 12. The crystal structure has been solved by direct methods and refined to a finalRvalue of 0.063 for 575 observed reflexions. Three independent molecules are found within the asymmetric unit; one of these displays a pseudo-cyclic form dictated by the occurrence of a strong intramolecular hydrogen bond. Conformational investigation of DMEAO in solution, using ir and nmr spectroscopy shows that this pseudo-cyclic form is more likely to occur in diluted states. These findings are related to the ability of this tertiary amine oxide to act as a good solvent, up to a water content of one water molecule per DMEAO molecule.

ISSN:0008-4042    

DOI:10.1139/v84-002

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Yields ofcis-1,2-cyclohexanediol formed by the reaction of methanol–water solutions of potassium permanganate with cyclohexene varied from nearly zero to a high of 84% as a function of stirring efficiency and dilution. This unusual effect is attributed to the formation of an intermediate hypomanganate ester ion which after formation may undergo reaction [1] with water to form the glycol or [2] with excess MnO4−to form higher oxidation products. The factor of increased stirring and dilution reduced localized excess of MnO4−and, thereby, minimized the contribution of reaction [2]. Addition of modest concentrations of methanol increased the yield, and this is attributed to enhanced solubilization and dispersion of the insoluble cyclohexene. Sodium hydroxide was beneficial to the reaction but only in low concentrations.

ISSN:0008-4042    

DOI:10.1139/v84-003

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

A series of substituted uracil analogues of the antiviral agent 9-[[2-hydroxy-1(hydroxymethyl)ethoxy]methyl]guanine (BIOLF-62) has been synthesized and characterized. The uracil analogues show little activity against herpesviruses.

ISSN:0008-4042    

DOI:10.1139/v84-004

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The association constants for Hg2+-complexes involving monomeric (TM) and dimeric (TD) forms of thymine are determined by pH-titration measurements made over a wide pH range 2 < pH < 11. In both systems, the experimental data have been analyzed by a pit-mapping method and the concentration distribution of the various complex species is plotted versus a pH gradient.Because of the tendency of Hg2+to form two bonds in a linear configuration, non-chelate complexes [Hg(TM)+] (log β101 = 10.65) and [Hg(TM)2] (log β102 = 20.70) are formed with the monomer thymine.Photodimers, obtained after irradiation of monomer thymine at 260 nm in frozen water (−10 °C), are the (meso)-cis,synforms and can be complexed by the Hg2+ions in [Hg(TD)] (log β101 = 13.55), [HgH−1(TD)]−(log β1−11 = 6.73), and [HgH−2(TD)]2−(log β1−21 = 1.69) species. [Hg(TD)] complex shows an absorption spectrum shifting towards 280 nm, whereas the free dimer ligand absorbs lower than 240 nm only. An irradiation at 280 nm provides the formation of the [Hg (TM)2] complex and consequently the breaking of the cyclobutane cycle in the dimer molecule.

ISSN:0008-4042    

DOI:10.1139/v84-005

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Abinitiominimal basis set STO-6G calculations show axial-SiF4•NH3andtrans-SiF4•2NH3to be energetically more stable with respect to SiF4and ammonia. All other geometrical isomers are 1.0–2.0 eV higher.Our calculation results rule out the steric hindrance between ligands as the reason SiF4•2NH3is, according to experimental evidences,ciswhile complexes of bulkier ligands aretrans.Since thecis-SiF4•2NH3has a large electric dipole moment and a suitable charge arrangement it is conceivably the favoured form in the solid phase. Thecis → transrearrangement may take place under conditions where the advantages of thecisare not operative.Although there is some degree of covalency in the Si—N bond it remains largely electrostatic, with the lone pair of ammonia attracted to the positively charged Si atom. The lone pair does not appear to be extensively altered by the complex formation.

ISSN:0008-4042    

DOI:10.1139/v84-006

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The crystal structure of diethylammonium tetrachloro(p-phenoxyphenyl)tellurate has been determined by the heavy atom method. The crystals are monoclinic, space groupC2/c, with unit cell dimensionsa = 19.675(5),b = 7.634(3),c = 28.716(6) Å, β = 105.58(2)°, andZ = 8. For 2636 "observed" reflections (I > 3σ(I)),R = 0.030. The primary geometry about tellurium is based on a square pyramid with a secondary interaction on the vacant side of the tellurium coordination octahedron. The ions are apparently linked by weak interionic hydrogen bonding along the crystallographicbaxis.

ISSN:0008-4042    

DOI:10.1139/v84-007

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The dissolution of a copper anode has been studied in aqueous solutions, at pH 4, for a range of concentrations varying from 0.1 Mto 1.2 Min NaBr. Where the accumulation of the corrosion product on the copper was nonexistent or negligible, two phenomena account for the dissolution current: a surface phenomenon and a phenomenon of diffusion of the ions into the solution. The current associated with each of these slow steps has been determined from the linear relationshipi−1vs. ω−1/2.The main characteristics of the copper anode behavior are expressed as partial derivatives:,,, while the reaction order for the bromide ions is equal to 2. Furthermore, the linearity of the relationshipEvs. log10iarises as a direct consequence of a surface phenomenon limited by an electron transfer. A dissolution model that describes the main characteristics of the copper dissolution is presented. According to this model, the termidis entirely ascribable to the diffusion of a copper bromide complex, CuBr2−, from the surface of the electrode into the solution. The apparent activation energy calculation is 7 kcal/mol according to the model, while the experimental value is 6.5 kcal/mol.Finally, the observed oxidation wave when the electrode potential becomes sufficiently anodic compared to the reversible potential of the reaction Cu + Br− = CuBr + e, is associated with the passivation of the copper by γ-CuBr. [Journal translation]

ISSN:0008-4042    

DOI:10.1139/v84-008

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Cyclotetraphosphazanes2and5obtained from 1,2-diamines are 1,3,2-diazaphosphole oligomers leading to the monomeric form by either thermal equilibrium or by complexing with boron trifluoride. The dicoordinated form stabilized by an orthophenylene ring could explain the reactivity of 4,5-benzo 1,3,2-diazaphosphole3with compounds having a mobile hydrogen; these reactions were a 1.2 type addition while butanol led to a 1.1 type addition with complexed 1,3,2-diazaphospholes4and8.

ISSN:0008-4042    

DOI:10.1139/v84-009

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Foam separation investigations over the 2.5–10.5 pH range show that U(VI) can be successfully separated from aqueous solutions by precipitation with oxine and subsequent flotation of the precipitate, either in absence or in presence of surfactant collectors. Collectors tested were: cetyl trimethyl ammonium bromide (CTAB) and sodium lauryl sulphate (NaLS). The extent of removal depends on many factors and removals as high as 98% could be achieved when uranyl oxinate precipitate was floated, under certain controlled conditions, in the presence of CTAB. Factors affecting the percentage removal were investigated and the best conditions were selected. The results obtained are discussed in terms of the hydrolytic behaviour of U(VI).

ISSN:0008-4042    

DOI:10.1139/v84-010

出版商:NRC Research Press    

年代:1984

数据来源: NRC