摘要:

AbstractThe photosensitized oxidation of methyl substituted phenols with freepara‐positions starts with an electrophilic attack of position 4 by singlet oxygen. This follows from the course of the reaction using phenols with methyl groups in different positions. The influence of the solvent shows that the hydroperoxide formation from the primary oxygen adduct proceeds via aninter‐molecular hydrogen shift. The solvent is the hydrogen donator, whereas the phenoxy radicals resulting from the oxidation of the phenol by the excited sensitizer are the hydrogen acceptors. Finally, the quinones are formed from the hydroperoxides by elimination of wa

ISSN:0018-019X    

DOI:10.1002/hlca.19700530702

出版商:WILEY‐VCH Verlag GmbH    

年代:1970

数据来源: WILEY

摘要:

AbstractFrom the root bark of the apocynaceaHedranthera barteri(Hook. f.)Pichonwere isolated the known indole alkaloids vobtusine (1), voacamine (2), callichiline (3), voacangine (4) and conoflorine (5), as well as the unknown plant bases amataine, goziline and owerreine, and also beninine and 1, 2‐dehydrobeninine. The structures of the two last mentioned alkaloids were shown in an earlier publication to be6and7, respectively. Amataine, goziline and owerreine are bis‐indole alkaloids, which on the basis of their chemical and spectroscopic (especially mass spectroscopic) properties have been assigned the structures8,9and10, respectiv

ISSN:0018-019X    

DOI:10.1002/hlca.19700530703

出版商:WILEY‐VCH Verlag GmbH    

年代:1970

数据来源: WILEY

摘要:

AbstractThe structure of panepoxydone (1) and some related products, produced by two species ofPanus(basidiomycetes), are proposed on the basis of chemical transformations and physical measurements.The absolute configurations of the main products are deduced by the interpretation of CD. studies and compared with those of the structurally related compounds epoxydone (10), terreic acid (11) and terremutin (12).

ISSN:0018-019X    

DOI:10.1002/hlca.19700530704

出版商:WILEY‐VCH Verlag GmbH    

年代:1970

数据来源: WILEY

摘要:

AbstractIn the benzilic acid type rearrangement oft‐butyl α,β‐dioxobutyrate (VII) the intactt‐butoxycarbonyl group is shifted to the β‐carbonyl c

ISSN:0018-019X    

DOI:10.1002/hlca.19700530705

出版商:WILEY‐VCH Verlag GmbH    

年代:1970

数据来源: WILEY

摘要:

AbstractSelective transport of potassium ions through synthetic membranes impregnated with valinomycin in octane‐2‐ol in the presence of equal amounts of K+and Na+or Li+ions is induced on application of a potential difference across these membranes. By using14C‐labelled valinomycin it is shown that transport of potassium ions is accompanied by an equivalent transport of valinomycin within the membrane, consistent with the formation of a 1 : 1 complex of K+with valinomycin. The exchange of ligands is shown to occur during the transport process so that a carrier‐relay mechanism, as proposed earlier for macrotetrolide‐mediated potassium transport, accounts for all experimental results on the bulk membrane

ISSN:0018-019X    

DOI:10.1002/hlca.19700530706

出版商:WILEY‐VCH Verlag GmbH    

年代:1970

数据来源: WILEY

摘要:

AbstractThe nuclear magnetic resonance spectra of a series of protonated organic nitrogen compounds in trifluoroacetic acid solution have been studied. A direct correlation between the exchange rate of the ammonium protons and the acidity constant of the functional group is established. Substituted anilinium and pyridinium ions with pKvalues below 4 show coalescence for the signals of N⊕H protons and disappearence of the coupling with the α pro

ISSN:0018-019X    

DOI:10.1002/hlca.19700530707

出版商:WILEY‐VCH Verlag GmbH    

年代:1970

数据来源: WILEY

摘要:

AbstractHeteronuclear spin tickling experiments in the degenerateA3Xspin system of a13CH3group have proved to be suitable for accurate carbon shift determinations in methyl groups. A weak perturbation of one of the13C quadruplet lines splits both proton doublet lines into a sub‐triplet with the relative signal strengths depending on whether an outer or inner13C line is irradiated. Deviation from exact resonance with one of the13C transitions modifies the relative intensities, and finally further splitting of the outer subtriplet lines occurs in accordance with theory. The amount of this additional splitting is equal to the difference between the double resonance frequency and the13C transition frequency to be measured. Signal distortions observed when the double resonance spectra are recorded in theINDORsweep mode have to be ascribed to the fact that the tickling effect competes with the generation of transient nutation

ISSN:0018-019X    

DOI:10.1002/hlca.19700530708

出版商:WILEY‐VCH Verlag GmbH    

年代:1970

数据来源: WILEY

摘要:

AbstractOxymercuration ofcis,cis‐1, 5‐cyclooctadiene (1), followed by treatment with potassium iodide and subsequent reaction with iodine, leads to six isomeric diiodides which represent the three possible stereoisomers2,3, and4of 2, 5‐diiodo‐9‐oxabicyclo[4.2.1]nonane as well as5,6, and7of 2, 6‐diiodo‐9‐oxabicyclo[3.3.1]nonane. The isolation, structure determination and some reactions of these diiodo compounds2

ISSN:0018-019X    

DOI:10.1002/hlca.19700530709

出版商:WILEY‐VCH Verlag GmbH    

年代:1970

数据来源: WILEY

摘要:

AbstractESR. spectra of the radical anion (I⊖) produced from dimethyl‐phenyl‐phosphine (I) both by electrolysis and reaction with alkali metals have been studied upon variation of temperature. The coupling constant assigned to the31P nucleus depends strongly on temperature, whereas the coupling constants attributed to protons do not exhibit such a dependence. The π‐spin populations at the benzene ring of I⊖give evidence ‐ in accordance with other experimental data [1] [2]– that the dimethylphosphino substituent is electron‐attracting. This effect is thought to be due mainly to P ← Cπdelocalization, which is analogous to the SiCπinteraction in trimethylsilyl‐substituted π‐systems [3].The ESR. spectrum previously [4] ascribed to I⊖is shown to arise from a secondary radical. The formation and structure of this

ISSN:0018-019X    

DOI:10.1002/hlca.19700530710

出版商:WILEY‐VCH Verlag GmbH    

年代:1970

数据来源: WILEY

摘要:

AbstractPrimary diazoketones, RCOCHN2, are O‐protonated in HFSbF5SO2or FSO3HSbF5SO2at −60°, as observed by NMR. The OH‐proton resonates at 9.3–9.6 δ and is coupled with HC 1 (J= 1–2.5 Hz). Secondary diazoketones, RCOC(N2)R, when protonated, give an OH‐singlet at 8.85 δ. The assignments are corroborated by use of deuterated diazoketones, RCOCDN2, or deuterated acid, FSO3D. Primary diazoketones react with FSO3H at −60° to −15°, giving products assigned the fluorosulfate structure, RCOCH2OSO2F; they do not exchange HC 1 with solvent before or during decomposition. Intermediate C‐protonated diazonium ions and α‐oxo‐carbonium ions (vinyl carbonium ions) have not been identified. 3‐Diazo‐4‐methyl‐2‐pentanone (VIII) reacts with FSO3H at −15°, eliminating N2and gi

ISSN:0018-019X    

DOI:10.1002/hlca.19700530711

出版商:WILEY‐VCH Verlag GmbH    

年代:1970

数据来源: WILEY