摘要:

The use of 3-carboxylated 2,5-dihydrothiophenes as the dienophilic component of the Diels–Alder reaction has been investigated. The yields are generally quite low. The formation of conjugated dienes that are aminated at an interior position of the conjugated chain by formation and thermal decomposition of 3-acetamido-2,5-dihydrothiophenes appears to be a viable route to these useful compounds. One example of the Diels–Alder reaction of 2-carboxylated diethyl vinylphosphonates is reported.

ISSN:0008-4042    

DOI:10.1139/v84-356

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Proton and carbon-13 nmr evidence is presented on the number, stoichiometry, geometry, and stability of the complexes which form when sodium tungstate and (D,L)-thiomalic acid are mixed in aqueous solution at pH values in the range 2–7. In particular, three (or four) complexes are detected having a 1:2 composition (metal–ligand), as well as a less stable complex which seems to be a 1:1 species. Preliminary data are also given on the exchange of bound ligand in these complexes.

ISSN:0008-4042    

DOI:10.1139/v84-357

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Lateropyrone, 5-hydroxy-9-methoxy-2-methyl-4H,6H-pyrano[3,4-g]-1-benzopyran-4,6-dione-8-carboxylic acid,1, has been isolated from cultures of the fungusFusariumlateritiumNees, and shown to have inhibitory activity against the growth of a gram-positive bacterium and a yeast. A crystal structure of the dimethyl derivative of lateropyrone,2, was determined. The crystals are monoclinic, space groupP21/c, witha = 9.663(4),b = 22.317(9),c = 7.747(5) Å, β = 113.03(4)°,Dc = 1.496 g cm−3,V = 1538(1) Å3,T = 25 °C, C17H14O8. The structure was refined toR = 0.0543 by least squares using 2100 observed, independent reflections measured on a 4-circle diffractometer, to obtain 241 parameters. The linearly fused tricyclic ring system is only approximately planar. In- and out-of-plane distortions are rationalized in terms of molecular overcrowding.

ISSN:0008-4042    

DOI:10.1139/v84-358

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

18F-labelled 1,3-bis-(2-fluoroethyl) nitrosourea (18F-BFNU) (9) and 1-(2-chloroethyl)-3-(2-fluoroethyl) nitrosourea (18F-CFNU) (isomeric mixture,11,12) were synthesized by nucleophilic attack of18F-labelled tetra-n-butylammonium fluoride on the aziridine ring of 1,3-substituted ureas. Diethyleneurea (DEU) (5), 1-(2-fluoroethyl)-3-ethyleneurea (FEU) (7), and 1-(2-chloroethyl)-3-ethyleneurea (CEU) (14) were used as starting materials in the synthesis. Nitrosation of18F-labelled 1,3-bis-(2-fluoroethyl) urea (18F-BFU) (6) produced18F-BFNU with a radiochemical yield of 5–10%. Nitrosation of18F-labelled 1-(2-chloroethyl)-3-(2-fluoroethyl) urea (18F-CFU) (15) gave18F-CFNU as a mixture of two isomers. Geometrical isomers of CFNU were separated by hplc, and the radiochemical yield of the two isomers ranged from 8% to 15%, with a radiochemical purity exceeding 96%. Syntheses, which took about 60 min, yielded products with specific activity of 680 mCi/mmol when n-Bu4N+F−was used, or 300 mCi/mmol when HF was used to complete the opening of the aziridine ring.

ISSN:0008-4042    

DOI:10.1139/v84-359

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The heterogeneous oxidation of sulfides and selenides by copper(II) permanganate octahydrate or a mixture of potassium permanganate and copper(II) sulfate pentahydrate has been studied. Conditions under which quantitative conversions of the sulfides and selenides to the corresponding sulfones and selenones take place have been determined and an attempt has been made to visualize a mechanism for the reaction.

ISSN:0008-4042    

DOI:10.1139/v84-360

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The Kolbe reaction of pyruvic and phenylglyoxylic acids in acetonitrile takes place with high yields of biacetyl and benzil, respectively. Electroluminescence is produced during the electrolysis. This luminescence can be attributed to phosphorescence following the generation of excited triplets of the α-diketones in the acyl radical recombination. The efficiencies of the triplet production, relative to ground state formation, were evaluated to be of the order of 8 × 10−3and 10−1for the recombination leading to benzil and biacetyl, respectively.

ISSN:0008-4042    

DOI:10.1139/v84-361

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

A Selected-Ion Flow Tube (SIFT) apparatus has been used to produce Xe+by electron impact and to study its reactions with C2N2. The2P3/2and2P1/2spin states of Xe+were observed to react differently: by C2N2addition to form Xe+•C2N2and by charge transfer to form C2N2+, respectively. Further ion–molecule reactions with C2N2were observed to establish polymeric ions of the type (C2N2)x+. The results indicate that the simple charge transfer model may be sufficient to account for the rate enhancement observed in the radiolytic polymerization of C2N2/Xe mixtures.

ISSN:0008-4042    

DOI:10.1139/v84-362

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The reaction of μ-peroxybis(ethylenediamine)bis(diethylenetriamine)cobalt(III) with ferrous ions has been studied by stopped flow spectrophotometry and by59Co nmr. Two separate initial reduction steps with second order rate constants of 1.07 and 3.04 M−1s−1, respectively, can be discerned in the stopped flow experiments. These two rate constants are assigned to inner sphere reduction of the aef,cd,b and edf,ac,b isomers of the peroxy cobalt complex, respectively. The different isomers can be distinguished by59Co nmr. If there is insufficient Fe2+present to completely reduce the complex to Co(II) and water, the change in the relative intensities of the59Co resonances after partial reduction shows that one isomer has reacted faster than the other. The59Co resonances can be assigned to the different isomers on the basis of a point charge model for the chemical shifts and line widths. Based on this model it is concluded that the isomer with the central NH of the diethylenetriaminetransto the peroxy ligand reacts faster. This result is compared to literature reports on the relative rates of substitution of isomers of Co(III) complexes with ethylenediamine and diethylenetriamine ligands.

ISSN:0008-4042    

DOI:10.1139/v84-363

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The relative conformation of the aromatic rings and the amide bridge as well as important details of the two side chains of the title compound in a DMSO-d6solution have been established by use of non-selective and selective proton spin-lattice relaxation times coupled with nOe experiments. The complete analysis of13C spin-lattice relaxation times has shown the main features of the dynamic behavior of the title compound.

ISSN:0008-4042    

DOI:10.1139/v84-364

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

5′-S-(2-Sulphoethyl)-5′-deoxy-5′-thioadenosine (S-adenosylcoenzyme M),5, was prepared from adenosine by reacting its 2′,3′-isopropylidine tosylate with the disodium salt of coenzyme M (NaSCH2CH2SO3Na) followed by removal of the protecting group. Methylation of5to give methylsulphonium (±)S-adenosylcoenzyme M,6, was achieved with methyl iodide in acetic acid. Neither5nor6stimulated methane production from cell free preparations ofM.thermoautotrophicum, negating the possibility of a biochemical analogy between6andS-adenosylmethionine (SAM).

ISSN:0008-4042    

DOI:10.1139/v84-365

出版商:NRC Research Press    

年代:1984

数据来源: NRC