摘要:

5-Amino-4,4-dibenzyl-3-one-2H-1,2,6-thiadiazine-1,1-dioxide was structurally characterized in the solid state by X-ray diffraction. The structure shows that the title compound exists in the solid in a sheet-packed form and as the amino tautomer. The unconjugated heterocyclic ring, which in the structures of related compounds is usually folded, is planar in the present structure.1H nuclear magnetic resonance and dipole moment data indicate that the title compound has the same structure in the solid state and in solution.

ISSN:0008-4042    

DOI:10.1139/v88-389

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The use of the air-stable complexes tetrachlorobis(μ-methoxy)bis(methanolo)dimethoxyditungsten (1) and tetrachlorobis(μ-ethoxy) tetraethoxyditungsten (2) as catalyst precursors for the metathesis of 1-octene is described. Using mild conditions, the latter was converted to 7-tetradecene (4) in fair yields when diethylaluminum chloride (3) was used as a cocatalyst. Product stereoselectivity was 4/1 in favor of thetransisomer. The reaction was also shown to be efficient for the production of 2-nonenes.

ISSN:0008-4042    

DOI:10.1139/v88-390

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Reaction of 3-acetoxymethyl-1-aryl-3-methyltriazenes with sodium thiophenolate or thiocresolate in anhydrous dimethylformamide affords a new series of 3-arylthiomethyltriazenes (2), Ar-S-CH2-NMe-N=N-Ar′. These triazenes are remarkably labile in aqueous buffer and may be good pro-drugs for the active metabolite of the antitumour dimethyltriazenes. The reaction of arenediazonium fluoroborates with 1,3-thiazolidine in aqueous acetone affords a new series ofN-arylazo-1,3-thiazolidines (4); the arylazothiazolidines represent a new class of triazene in which the N3 nitrogen is incorporated into a heterocyclic unit, in this case a 1,3-thiazolidine. Nuclear magnetic resonance spectra of the arylazothiazolidines show evidence for rotational isomerism of the exocyclic N2—N3 bond in the triazene moiety.

ISSN:0008-4042    

DOI:10.1139/v88-391

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The15N and13C chemical shifts of the sodium salt of deoxycytidylyl-(3′,5′)-guanosine have been measured in dimethylsulfoxide in the presence of variable amounts of CF3COOH. N3(cyt) is protonated first, followed by N7(gua) and the phosphate anion. These results vary from those reported for the binding of the methylmercuric cation to d(CpG).

ISSN:0008-4042    

DOI:10.1139/v88-392

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The crystal structures of two 16-alkyl thebaine and oripavine analogues are described, in an attempt to put forward the particular requirements of these compounds to interact with the opiate receptor. Conformational congruencies accounting for the very high potency of these compounds are also emphasized.In light of the crystal structures, the influence of the 16-alkyl substitution is discussed, as well as the differentiation in the agonist activity observed between diastereomers at C(19) characterizing these classes of opioids.Significant distortions in the condensed ring system and the existence of an intramolecular hydrogen bonding are the main geometrical observations. They are invoked to account for particular modulations in the analgesic activity.

ISSN:0008-4042    

DOI:10.1139/v88-393

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Free, unsolvated phenylium ions formed by the spontaneous decay of 1,4-ditritiobenzene have been allowed to react with gaseous cyclic ethers (oxirane, propene oxide, and oxetane) and acetaldehyde in the pressure range 30–250 Torr and in the presence of a thermal radical scavenger (O2, 4 Torr). The effects of a gaseous base (NMe3, 20 Torr) and of an energy moderator (He, 630–720 Torr) were also investigated. Phenylium ion confirms its considerable site selectivity, demonstrated by the distinct preference for then-type center of the substrate, although appreciable insertion into the carbocyclic structure of propene oxide and oxetane is observed as well. The stability features of the ionic intermediates from addition of phenylium ion to selected substrates have been evaluated as well as their fragmentation and isomerization mechanisms. The behavior of gaseous phenylium ion toward cyclic ethers, in particular its ability to formally abstract an oxygen atom from the ether to give the phenoxenium ion, a reaction first observed in the present study, is discussed and compared with previous mechanistic investigations carried out in the gas phase and in solution.

ISSN:0008-4042    

DOI:10.1139/v88-394

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The syntheses, in ethereal solvents, of the complexes of 15-crown-5 and cyclohexano-15-crown-5 with lithium, sodium, and potassium phenoxide are described. The two macrocycles form complexes with lithium and sodium phenoxide with host:guest ratios of 1:2. Potassium phenoxide, however, was complexed by the two macrocycles to give products with macrocycle:salt ratios of 1:1. Crystals of 15-crown-5•2LiOPh were obtained for X-ray diffraction structure determinations. In fact, the crystal structures of two co-crystallizing polymorphs of this complex (1aand1b) have been determined. Polymorph1acrystallizes in space groupwitha = 11.386(4),b = 11.901(4),c = 10.654(4) Å, α = 106.53(3), β = 112.60(3), γ = 106.52(3)°, andZ = 2. Polymorph1bcrystallizes in space groupP21/nwitha = 15.355(4),b = 11.642(2),c = 13.595(6) Å, β = 104.56(3)°, andZ = 4. Both structures were solved by direct methods, and refined by full-matrix least-squares calculations to residuals,R, of 0.053 and 0.055 for polymorphs1aand1b, respectively. The structures of the two polymorphs differ only in the orientation of the phenoxides. The structures show a dimer, (15-crown-5•2LiOPh)2, which consists of an aggregate of four lithium phenoxide molecules complexed by two 15-crown-5 macrocycles. The two lithiums of each monomeric unit of this dimer have different crystallographic and chemical environments. One lithium is coordinated to all five oxygens of the macrocycle and to one of the phenoxide oxygens while the other lithium is coordinated to only one oxygen of the macrocycle and to three phenoxide oxygens.

ISSN:0008-4042    

DOI:10.1139/v88-395

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The kinetics of the reduction of the 3-cyano-1-methylquinolinium, 4-cyano-2-methylisoquinolinium, and 2-methyl-5-nitro-isoquinolinium cations by 9,10-dihydro-10-methylacridine, and also the reduction of these same three cations as well as the 10-methylacridinium cation by 5,6-dihydro-5-methylphenanthridine, have been investigated in 20% acetonitrile – 80% water, ionic strength 1.0, 25 °C. The reactions of the 2-methyl-5-nitroisoquinolinium cation with both reductants, and also of the 4-cyano-2-methylisoquinolinium cation with 9,10-dihydro-10-methylacridine, display kinetic saturation effects in the pseudo-first-order rate constants as a function of heterocyclic cation concentration. These effects are consistent with the formation of 1:1 association complexes between hydride donor and acceptor prior to the rate-determining step of the reduction. The second-order rate constants for these reactions, and also those for analogous heterocyclic cation reductions by 1,4-dihydronicotinamides, show systematic variations as a function of the hydride donor and acceptor species.

ISSN:0008-4042    

DOI:10.1139/v88-396

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Charge-transfer complexation ofN,N-dimethyl-p-toluidine (DMT) with each of the followingN-methyl cations has been investigated in acetonitrile solution at 25 °C: acridinium; phenanthridinium; 3-X-quinolinium and 4-X-isoquinolinium (X = H, Br, CONH2, CN); 5-nitroisoquinolinium; 3-X-pyridinium (X = CONH2, CN) (also theN-benzyl pyridinium cations);N,N′-dimethyl-4,4′-dipyridylium dication. Charge-transfer absorption maxima are reported, and extinction coefficients (ϵmax) at these maxima and association constants (K) for 1:1 complex formation have been evaluated from the dependence of absorbance upon [DMT]. In general, the longest wavelength absorption maximum increases with increasing association constant. There is a strictly linear relationship between ϵmaxand 1/K. These observations are considered in the context of theories of charge-transfer spectra. Such charge-transfer species are considered as models for the association complexes that are believed to exist upon the reaction pathway for hydride transfer between heteroaromatic cations. Although some significant qualitative relationships are apparent, variations in susceptibility of heteroaromatic cations to charge-transfer complexation are much smaller than variations in the reactivity of these cations towards hydride donor species.

ISSN:0008-4042    

DOI:10.1139/v88-397

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The kinetics of racemization of 2,4-disubstituted-5(4H)-oxazolones obtained fromN-acetyl,N-benzoyl, andN-benzyloxycarbonylglycyl-L-leucine, -valine, and -phenylalanine have been studied in several solvents alone and in the presence of tertiary amines. The influence of the nature of the substituents on the rate of the reaction has been evaluated, and the values of the activation parameters ΔH≠and ΔS≠for the base-catalyzed reactions have been determined. The racemization process is governed by electronic effects of the C(2)-substituents and steric effects of the C(4)-substituents of the oxazolones. The thermodynamic data suggest that the 2-substituted-4-benzyl-5(4H)-oxazolones racemize more readily than the 4-alkyl analogues (alkyl ≠ benzyl) because of the unique conformation assumed by the benzyl substituent. The rate of the base-catalyzed reaction depends on the extent of hindrance about the nitrogen atom of the tertiary amine as well as on its basicity. The data suggest that the relative rates of racemization of oxazolones are not a true reflection of the relative tendencies to racemize of the pertinent residues during couplings of the parent acids.

ISSN:0008-4042    

DOI:10.1139/v88-398

出版商:NRC Research Press    

年代:1988

数据来源: NRC