ISSN:0018-019X    

DOI:10.1002/hlca.19740570802

出版商:WILEY‐VCH Verlag GmbH    

年代:1974

数据来源: WILEY

摘要:

AbstractPhysical adsorption of the title compounds on rhombic sulfur of 0.4 to 0.5 m2/g is reported. The isotherms are of type II for N2, Ar and C5H12, of type III for SO2and CO2, and linear for SF6. There is no hysteresis. The method ofRoss&Oliviershows that the surface is relatively heterogenous (γ 17). Isosteric heats of adsorption and c values of the B.E.T. equation are also reported

ISSN:0018-019X    

DOI:10.1002/hlca.19740570803

出版商:WILEY‐VCH Verlag GmbH    

年代:1974

数据来源: WILEY

摘要:

The preparation of a number of 4‐substituted quinuclidines and the PKavalues of their hydroperchlorates in water are reporte

ISSN:0018-019X    

DOI:10.1002/hlca.19740570804

出版商:WILEY‐VCH Verlag GmbH    

年代:1974

数据来源: WILEY

摘要:

The preparation of several 4‐heterosubstituted quinuclidines and the pKavalues of their hydroperchlorates in water are reporte

ISSN:0018-019X    

DOI:10.1002/hlca.19740570805

出版商:WILEY‐VCH Verlag GmbH    

年代:1974

数据来源: WILEY

摘要:

AbstractThe electron transfer spectra of the hexachloro‐ and hexabromoniobate (V), and‐tantalate(V) anions are investigated with particular care to avoid hydrolysis products. New interpretations are given, and the optical electronegativities χ of Nb(V) and Ta(V) are recalculated. The difference between both χ values is 0.2, in better agreement with the differences observed for metals of the second and third transition s

ISSN:0018-019X    

DOI:10.1002/hlca.19740570806

出版商:WILEY‐VCH Verlag GmbH    

年代:1974

数据来源: WILEY

摘要:

The main product of the reaction between 2‐aminobenzimidazole and dimethyl acetylenedicarboxylate is shown to be methyl 1, 2‐dihydro‐2‐oxo‐pyrimido[1, 2‐a]benzimidazole‐4‐carboxylate (6), which can be methylated at position 1 to give7. Catalytic hydrogenation of7leads to the 1,2,3,4‐tetrahydro derivative8, whereas NaBH4reduces the ester and, to some extent, the double bond to yield a mixture of9and10. When a 1‐substituted 1, 2‐dihydro‐4‐hydroxymethyl‐pyrimido[1, 2‐a]benzimidazol‐2‐one (for example11) is catalytically hydrogenated, the double bond is unaffected, but hydrogenolysis of the alcohol group occurs instead to give13. The lactam group is less stable in the tetrahydro series than in the dihydro compounds. For example, the lactam is cleaved when8is treated with amines containing a small amount of water, and the monoamides16and17are formed. Similarly, sodium hydroxyde cleaves the lactam under mild conditions to the dicarboxylic acid19, which can be converted to 2, 3‐dihydro‐1‐methyl‐2‐oxo [1H]imidazo[1, 2‐a]benzimidazole‐3‐acetic acid (4‐methyl)piperazide (20) with thionyl chloride and N‐methylpiperazine. However, when7is treated with methylamine at low temperature, the amide22is formed, whilst at room temperature the amine attacks both the ester and the double bond to giv

ISSN:0018-019X    

DOI:10.1002/hlca.19740570807

出版商:WILEY‐VCH Verlag GmbH    

年代:1974

数据来源: WILEY

摘要:

The crystal structure of 1,2,3,4‐Tetrahydro‐1‐methyl‐2‐oxopyrimido[1,2‐a]benzimidazol‐4‐carboxylicacid‐methylester was investigated by an X‐ray analysis in order to determine unequivocally the positions of the substituents. The triclinic structure was solved by the multisolution method and refined to an R = 0.0302 with 1486 structure factors for 222 st

ISSN:0018-019X    

DOI:10.1002/hlca.19740570808

出版商:WILEY‐VCH Verlag GmbH    

年代:1974

数据来源: WILEY

摘要:

New simplified syntheses of two naturalp‐diquinonic pigments, phoenicine and oosporeine, have been described. By similar procedures, the syntheses of two other related diquinones have been carried out: 3,3′,6,6′‐tetrahydroxy‐biphenyl‐di‐p,p′‐quinone and 3,3′,6,6′‐tetrahydroxy‐4‐methyl‐biphenyl‐di‐p,p′‐quinone. The latter structure had been assigned to pyxiferine, which had been reported to be co

ISSN:0018-019X    

DOI:10.1002/hlca.19740570809

出版商:WILEY‐VCH Verlag GmbH    

年代:1974

数据来源: WILEY

摘要:

The biosynthesis of phoenicine and of oosporeine by intact cells ofPenicillium phoeniceumVANBEYMAand ofChaetomium aureumCHIVERSrespectively, has been investigated. Starting from acetic acid, biosynthetic sequences have been proposed; they are based on the incorporation of radioactivity into the two pigments of labelled, biochemically probable precursors. Orsellinic acid appears as a common intermediate, which is converted by multistep processes to 2,3,5‐trihydroxytoluene or to 2,3,5,6‐tetrahydroxytoluene. Oxidative coupling of two molecules of the triphenol furnishes the reduced form of phoenicine. Similarly, coupling of two molecules of the tetraphenol gives leuco‐oosporeine. Both leuco‐derivatives are easily dehydrogenated, under physiological conditions, with formation of the diquinones. Coupling occurs when the monophenyl derivatives contain the required number of OH groups in suitable po

ISSN:0018-019X    

DOI:10.1002/hlca.19740570810

出版商:WILEY‐VCH Verlag GmbH    

年代:1974

数据来源: WILEY

摘要:

AbstractHeptalene – a very unstable compound – can be reduced by lithium at −80° into its dianion.1H‐ and13C‐NMR. studies indicate that this dianion, contrary to the neutral molecule, has its π‐bonds delocalized. The magnetic field induces in this species a large diamagnetic ring current. The dianion of heptalene is thermally very stable, much more so than the neutral compound. All these observations point to an appreciable stabilization energy associated with the 14°‐electron system; this stabilization energy is probably large enough to impose a planar geometry

ISSN:0018-019X    

DOI:10.1002/hlca.19740570811

出版商:WILEY‐VCH Verlag GmbH    

年代:1974

数据来源: WILEY