摘要:

Crystals of bis(perchlorato) (γ-C-meso-5,5,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane)copper(II) are monoclinic,a = 14.061(1),b = 8.908(1),c = 19.710(1) Å, β = 90.912(5)°,Z = 4, space groupP21/c. The structure was solved by Patterson and Fourier syntheses and was refined by full-matrix least-squares procedures to a finalRof 0.054 andRwof 0.069 for 2945 reflections withI ≥ 3σ(I). The copper(II) ion has tetragonally distorted octahedral coordination geometry. The four nitrogen atoms of the macrocyclic ligand occupy the equatorial sites and two perchlorate oxygen atoms are in the axial positions. Bond lengths (corrected for libration) are: Cu—N, 2.024(4)–2.051(4), Cu—O, 2.657(5) and 2.697(5), Cl—O, 1.420(4)–1.473(6), N—C, 1.463(6)–1.508(6), and C—C, 1.498(8)–1.542(8) Å.

ISSN:0008-4042    

DOI:10.1139/v78-042

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The rates of reactions ofN-aryl-cis-2,3-diphenyl aziridines (4a–d) with dimethyl acetylenedicarboxylate (DMAD) are dependent only on aziridine concentration suggesting slow conversion of aziridines to azomethine ylides which subsequently react in 1,3-dipolar cycloadditions to yield Δ3-pyrrolines. The Hammett reaction constant (−0.80) determinee for theN-substituents in the slow ring opening further suggests direct generation of azomethine ylides from these aziridines. The stereochemistry of the cycloaddition products derived fromcis-1,2,3-triphenylaziridine with DMAD, maleic anhydride, dimethyl maleate, and dimethyl fumarate is consistent with the conrotatory generation of the ylides followed by their stereospecificcis-ciscycloaddition to the dipolarophiles.Similarly, cycloaddition of 7-aryl-6a,7a-dihydroacenaphtha-[1,2]-aziridines (5a–f) with DMAD yields bicyclic Δ3-pyrrolines and the rate is dependent only on aziridine concentration. This suggests the reaction proceeds via a slow disrotatory cleavage of the aziridine rings producing azomethine ylides which undergo subsequent addition to DMAD. The Hammett reaction constant for the ring opening step is +0.74 suggesting that the transition state for the ring cleavage is electron deficient in the aziridinyl ring but the cycloaddition reactions of5awith isomeric dipolarophiles as well as several dienes and cycloheptatriene reveal only stereospecific 1,2-cycloadditions expected of an azomethine ylide intermediate.

ISSN:0008-4042    

DOI:10.1139/v78-043

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The irradiation ofN-aryltriphenyliminophosphoranes in inert solvents leads to efficient production of triphenylphosphine and the diaryl azo compounds derived from theN-aryl ylide substituent. The irradiation ofN-alkyltriphenyliminophosphoranes leads to rearrangements of theN-alkyl substituent analogous to those observed during the irradiation of the corresponding azides. Triphenyliminophosphoranes which possessN-substituents capable of strong delocalization of the nitrogen lone pair (e.g. benzene sulfonyl, benzoyl) are photostable. Since all attempts to trap nitrene intermediates suspected to be formed during the photoreactions of the photolabile iminophosphoranes were unsuccessful, the reactions are considered to proceed via excited ylide intermediates.

ISSN:0008-4042    

DOI:10.1139/v78-044

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The magnitudes and signs of two-bond13C–1H coupling constants (2J) in the array O—13CA—CB—1H, appear to be determined by the relative orientations of the O—13CAand CB—1H bonds, as shown with a variety of carbohydrate derivatives. The data have been observed from natural abundancelH-coupled13C nmr spectra, and signs of2Jhave been determined by the 'selective population transfer' technique. When CBbears one oxygen atom, the observed2Jvalues range from −6 to 0 Hz, whereas a range of 0 to +8 Hz is found when CBbears two oxygen atoms. By contrast, for arrays in which CBbears one oxygen atom and CBtwo, the2Jvalues vary from −6 to +6 Hz. In general, the results confirm earlier indications that the larger the torsional angle between the O—13CAand CB—1H bonds, the more positive is the value of2J. These findings are supported by calculations for model compounds, i.e., propane-1,1,2-triol and butane-2,3-diol.

ISSN:0008-4042    

DOI:10.1139/v78-045

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Photolysis of 1,2-dipropyl-3,5-diethyl-1,2-dihydropyridine4, at λ > 300 nm, results in the opening of the ring to give an iminodiene5, which upon reduction leads to an aminodiene6. The imine5releases propylamine at acid pH. The dihydropyridine4is a model for analogous dihydro compounds which cross-link polypeptide chains in elastin. Thus photolysis would seem to be a specific method for breaking this type of cross-link in the insoluble fibrous protein.

ISSN:0008-4042    

DOI:10.1139/v78-046

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Aucantene (1) bas been synthesized from propynal in three stages involving the conjugate addition of lithium di-(E)-propenylcuprate to α,β-unsaturated aldehyde2as a key step.

ISSN:0008-4042    

DOI:10.1139/v78-047

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Thermolyses in polar solvents, of Δ3-1,3,4-oxadiazolin-2-ones or 2-phenylimino-Δ3-1,3,4-oxadiazolines derived from α,β-epoxyketones, yields acetylenic carbonyl compounds. Good yields of acetylenic aldehydes and ketones are obtained for those cases in which the epoxide is ring fused. Extension to acyclic cases failed primarily due to predominance of a parallel decomposition pathway. The method complements the procedures developed by Eschenmoser and co-workers for the conversion of, α,β-epoxyketones into acetylenic carbonyl compounds.

ISSN:0008-4042    

DOI:10.1139/v78-048

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Diketonato complexes of titanium(IV), (X3Ti(dik))2(X = Cl, Br; dik = anions of dipivaloylmethane and benzoylacetone), of apparent five-coordinate stoichiometry have been prepared and investigated in nitrobenzene solutions using the variable temperature nuclear magnetic resonance technique. The nmr spectra reveal the existence of two equilibrium species; a five-coordinate X3Ti(dik) and a six-coordinate X2Ti(dik)2complex. The data are interpreted in terms of a symmetric dissociation of the six-coordinate titanium(IV) dimer, (X3Ti(dik))2, into two five-coordinate monomers which then undergo a disproportionation reaction to the four-coordinate titanium tetrahalide and the six-coordinate X2Ti(dik)2species.

ISSN:0008-4042    

DOI:10.1139/v78-049

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A synthesis of the cyclohexapyrrolizidines32and33is described; the structure of the latter was determined by X-ray crystallography. It is anticipated that this synthesis will serve as a model for the construction of a similar pyrrolizidine system during a projected synthesis of thelepogine2.A convenient method for theC-methylation of cyclic vinylogous amides is also described. This procedure, which is similar to published procedures, affords high yields of methylated product and is regiospecific.

ISSN:0008-4042    

DOI:10.1139/v78-050

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Nucleoside analogs, namely 6-benzamido-9-(3-benzoyl-4(R))-methoxycarbonyl-2,2-dimethyl-thiazolidin-5(S)-yl)-9H-purine(7)and 6-chloro-9-[(3-benzoyl-2,2-dimethylthiazolidin-4(R)-yl)methyl]-9H-purine (8), were obtained from 3-benzoyl-5(S)-benzoyloxy-4(R)-methoxycarbonyl-2,2-dimethylthiazolidine (23) and 3-benzoyl-4(R)-hydroxymethyl-2,2-dimethylthiazolidine (24), respectively, the former, by treatment with 6-benzamidochloromercuripurine and titanium tetrachloride in 1,2-dichloroethane and the latter, by treatment with 6-chloropurine, triphenylphosphine, and diethyl azodicarboxylate in tetrahydrofuran. Compound23was obtained from 3-benzoyl-4(R)-methoxycarbonyl-2,2-dimethylthiazolidine (13) by treatment with benzoyl peroxide in refluxing benzene whereas compound24was obtained from13by borohydride reduction. The stereochemistry of the isomeric sulfoxides18aand18b, obtained from13by treatment withm-chloroperbenzoic acid, was assigned by means of1Hmr spectroscopy. Reaction of the sulfoxides18aand18bunder the Pummerer-reaction conditions afforded the rearranged product, 4-benzoyl-3(R)-methoxycarbonyl-5-methyl-3,4-dihydro-2H-1,4-thiazine (20). The chiral shift reagent, tris-[3-(trifluoromethylhydroxymethylene)-d-camphorato]europium(III), was used to confirm the enantiomeric purity of the key intermediates and the product nucleosides. The carbon-13 nmr spectra of the key compounds are reported.

ISSN:0008-4042    

DOI:10.1139/v78-051

出版商:NRC Research Press    

年代:1978

数据来源: NRC