摘要:

N-Heterocyclic cations form with substituted pentacyanoferrates a series of outer-sphere complexes of general formula Fe(CN)5L//N-Het, suitable for systematic studies in aqueous solution. The equilibrium constants for the association of dipositive cations (e.g.N,N′-dimethyl-4,4-bipyridyl, or paraquat ion) and monopositive cations (e.g.N-methylpyrazinium) with the hexacyanoferrate(II) anion are typically in the range of 30–40 M−1and 10–13 M−1. The optical charge-transfer energies depend on the nature of theN-heterocyclic acceptor, and on the binding properties of the ligand L as they modify the ionization potentials of the Fe(CN)5Ln−complexes. A linear correlation between the optical charge-transfer energies and ΔE0was found, with a slope (ΔEop/ΔG0) of 1.03 ± 0.03. The results were interpreted on the light of Hush's theory for intervalence transitions, with the aid of the equationEop = 2(ΔG11* + ΔG22*) + ΔG120, which correlates the optical energy (Eop) for electron-transfer with the intrinsic barriers (ΔG11* + ΔG22*) of the donor and acceptor ions, and the free energy change (ΔG120) for the process.

ISSN:0008-4042    

DOI:10.1139/v79-333

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The 1,2-trans-octaacetates of cellobiose, lactose, and maltose were converted to β-glycosides of 8-ethoxycarbonyloctanol in good yield by a single step reaction. A 1,2-acetoxonium ion generated by stannic tetrachloride in dichloromethane at −10 °C leads initially to β-glycosides via 1,2-orthoacetate intermediates.Insituanomerisation of the β-maltoside occurred during reaction (4 h) at room temperature and provided a preparative route to this α-glycoside of the disaccharide. The β-lactose and cellobiose glycosides were also anomerised to the respective α-glycosides. The three β- and three α-disaccharide glycosides of the disaccharides have been functionalised for conversion to artificial carbohydrate antigens.

ISSN:0008-4042    

DOI:10.1139/v79-334

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The three disaccharides lactose, cellobiose, and maltose in the form of their acetylated glycosyl bromides have been reacted with 8-ethoxycarbonyloctanol to provide the 1,2-trans-glycosides. Conventional Koenigs–Knorr and Helferich conditions provided these glycosides in poor yield but silver trifluoromethanesulphonate,N,N-tetramethylurea gave the disaccharide glycosides in 50–60% yield. Use of 2,4,6-trimethylpyridine as proton acceptor provided the corresponding 1,2-orthoacetates in 60–70% yield. These 1,2-orthoesters were rearranged by stannic tetrachloride to the 1,2-trans-glycosides. The isolation of acetylated 8-ethoxycarbonyloctanol from Lewis acid catalysed isomerisation of 1,2-orthoesters and from Koenigs–Knorr reactions in whichN,N-tetramethylurea was the proton acceptor is discussed in terms of a reaction mechanism proceeding from glycosyl halide to glycosidic products via a 1,2-orthoester intermediate. This proposal is supported by1H nmr evidence for the presence of 1,2-orthoacetate in Koenigs–Knorr reaction mixtures, and by 1,2-orthoacetate isomerisation to glycoside by the conjugate acid ofN,N-tetramethylurea.

ISSN:0008-4042    

DOI:10.1139/v79-335

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The oxidation potentials ofcis- andtrans-1,2-diphenylcyclopropane (1) andcis- andtrans-2,3-diphenyloxirane (2) have been determined by cyclic voltammetry, spectroscopically (using an empirical correlation of the long wavelength transition of the charge-transfer complexes with tetracyanoethylene) and by using an empirical correlation based upon the gas phase ionization potentials measured by photoelectron spectroscopy. The values obtained by these three very different techniques agree to within ±0.15 V. The results are interpreted in terms of the initial formation of the phenyl radical cation with the three-membered ring intact. The higher oxidation potentials ofcis- andtrans-2, relative to those ofcis- andtrans-1, are attributed to inductive electron withdrawal from the phenyl group by the oxygen of the oxirane ring. The relevance of these results to the photosensitized (electron transfer) behaviour of these compounds is discussed.

ISSN:0008-4042    

DOI:10.1139/v79-336

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

trans-(E)-2-Methyl-6-methylamino-2-hepten-1-ol (6) andcis-(Z)-2-methyl-6-methylamino-2-hepten-1-ol (13), two in vivo metabolites from the antispasmodic agent isometheptene (2), ((±)–N,1,5-trimethyl-4-hexenylamine) have been synthesized. In the first synthesis of thetransisomer, theN-trifluoroacetyl derivative of2was oxidized with selenium dioxide in ethanol to givetrans-2-methyl-6-N-methyltrifluoroacetamido-2-hepten-1-al (4). Aldehyde (4) was converted to6by reaction with sodium borohydride in ethanol. In the second synthesis,trans-2-methyl-6-oxo-2-hepten-1-ol ethylene ketal (8) andcis-2-methyl-6-oxo-2-hepten-1-ol ethylene ketal (11) were hydrolyzed without isomerization to hydroxyketones9and12. Both9and12were reductively aminated to the desired metabolites,6and13.

ISSN:0008-4042    

DOI:10.1139/v79-337

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Resonant ejection of ion species from the quadrupole ion store (QUISTOR) is shown to reveal the coupling of reactant ions with product ions in ion/molecule reactions studied with the QUISTOR – quadrupole mass filter combination. The technique involves the use of selective ejection of a chosen ionic precursor and the simultaneous observation of the perturbations in the concentration of product ions. The technique is demonstrated in studies of the ion chemistry and reaction kinetics of two known chemical systems.

ISSN:0008-4042    

DOI:10.1139/v79-338

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Regiospecific formation of 10-allyl-1-ketoquinolizidine (7) is achieved in high yield by a [2.3] sigmatropic rearrangement ofN-allyl-1-ketoquinolizidinium bromide (6). Wolff–Kischner reduction of7affords 10-allylquinolizidine (8) contaminated by the 10-propyl and 10-ethynyl analogs in amounts which depend on the reaction conditions. The carbon-13 spectrum of8indicates atrans-fused ring system with an axial substituent at C-10.

ISSN:0008-4042    

DOI:10.1139/v79-339

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

13C nmr confirms that coordination of metal ions by pyridoxine is through the C-3 and C-4′ oxygens in aqueous solution. Nitrogen appears to become more effective as a donor site in water–dimethylsulfoxide mixtures, while with increasing proportions of DMSO some cations are coordinated by DMSO rather than by pyridoxine. Changes in13C spin–lattice relaxation times on metal ion coordination are more informative about metal binding sites than changes in13C chemical shift. Some analogous results are reported for pyridoxamine.

ISSN:0008-4042    

DOI:10.1139/v79-340

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

An efficient synthesis (stereo- and regiospecific) of compoundI(Scheme I) fromo-cresol is described.

ISSN:0008-4042    

DOI:10.1139/v79-341

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The results of an1H and13C nmr study of the threesyn-pyridine aldoximes are reported. Observed6J(Hα,Hpara) values in the 2- and 3-pyridine aldoximes indicate that the oxime group is twisted approximately 20° out of the pyridine ring plane. Stereospecific5J(Hα,Hmeta) values measured for acetone solutions of 2-pyridine aldoxime indicate that the ratio of the NCCNtransconformation to the NCCNcisconformation is 0.86 ± 0.14. The results of similar measurements on 3-pyridine aldoxime give 0.60 ± 0.10 for the ratio of the C2CCNtransand C2CCNcisconformations.Abinitiomolecular orbital calculations are in good qualitative agreement with experiment. Carbon-13 chemical shifts of the oximes are compared with those previously measured for the parent aldehydes.

ISSN:0008-4042    

DOI:10.1139/v79-342

出版商:NRC Research Press    

年代:1979

数据来源: NRC