摘要:

AbstractThe structure of the title compound, a tricyclic Ni(II) tetra‐amine complex has been determined from analysis of photographic X‐ray data. The crystal system is orthorhombic, space groupP212121, with unit cell dimensionsa= 9.802,b= 8.998,c= 24.378 Å. The Ni atom is square planar coordinated. The six‐membered chelate ring has a chair conformation. One of the five‐membered chelate rings has a distortedgauche(λ) conformation with the methyl substituent in an equatorial position, the other has an unsymmetricalgauche(δ) conformation with the methyl substit

ISSN:0018-019X    

DOI:10.1002/hlca.19760590402

出版商:WILEY‐VCH Verlag GmbH    

年代:1976

数据来源: WILEY

摘要:

AbstractThe 70 eV mass spectra of a number of13C‐ and D‐labelled analogs of 1‐heptene have been measured, as well as the metastable transitions in the non‐labelled compound. Isotopic distributions in the major fragment ions have been calculated from the high and low resolution data. The results show that considerable skeletal rearrangement must take place before formation of most of the fragment ions. Loss of methyl and ethyl radicals occurs mainly from the two ends of the molecule. Ethylene fragments come primarily from the unsaturated end of the molecule, but show evidence of significant prior skeletal rearrangement. The predictedMcLaffertyrearrangement accounts for only 2/3 of the C4H8+ions formed, less for the C3H6+ions. At least 80% of C4H9+ions appear to be formed by allylic cleavage, as expected, but this mechanism can only account for a maximum of 20% of the formation of the complementary ion C3H5+. Both, this latter ion and C3H6+, are probably generated by loss of hydrogen from C3H7+.Figures obtained for label retention in 1‐[13C]‐ and 1‐D‐labelled analogs were nearly identical for most fragment ions, probably indicating that the hydrogen atoms in position 1 remain on C(1) even following skeletal rearrangement. A similar result was found for the 7‐[13C]‐ and 7‐D‐labelled compounds. The main exceptions in the case of the products labelled in position 1 (C4H7+, C3H3+) seem to be due to initial loss of an hydrogen atom from this position followed b

ISSN:0018-019X    

DOI:10.1002/hlca.19760590403

出版商:WILEY‐VCH Verlag GmbH    

年代:1976

数据来源: WILEY

摘要:

Synthesis of 4,9(11)‐androstadiene‐3,17‐dione.The total synthesis of 4,9(11)‐androstadiene‐3,17‐dione (23) is described starting from (1S, 7 aS)‐1‐t‐butoxy‐7a‐methyl‐5,6,7,7a‐tetrahydroindan‐5‐one (8) as a CD‐building block. The key step involves alkylation of8with 1‐chloro‐7,7‐o‐phenylenedioxy‐octane‐3‐one (14) a novel AB‐synthon to give the diketone15.15is converted to the secosteroid20viathe diene enol ether17using a previously described procedure. Low temperature methylation of20affords predominantly the 10β‐methyl compound21, w

ISSN:0018-019X    

DOI:10.1002/hlca.19760590404

出版商:WILEY‐VCH Verlag GmbH    

年代:1976

数据来源: WILEY

摘要:

AbstractThe total synthesis of the important natural product biotin1from the readily available keto diester3is described. This approach features the stereospecific hydrogenation of the thiophene intermediate19as the key synthetic step.The required differentiation of the diacid functionality of compound7is achieved by selective lactam formation with the terminal acid to yield the 8‐membered lactam8. A modifiedCurtiusreaction then affords the rearranged diurethane18through a series of acyl transfers. Finally, a novel conversion of the 3, 4‐diurethane moiety to the imidazolidone portion of biotin is utilized to complete the synthe

ISSN:0018-019X    

DOI:10.1002/hlca.19760590405

出版商:WILEY‐VCH Verlag GmbH    

年代:1976

数据来源: WILEY

摘要:

Addition‐elimination reactions from germanium heterocycles.II. 2‐Germa‐1,3‐diazolidines (X  Y  NMe).The reactivity of 2‐Germa‐1,3‐diazolidines with unsaturated compounds such as heterocumulenes (CS2, PhNCO, PhNCS) and with carbonyl compounds (aldehydes and ketones) has been investigated. Generally the formation of mono‐ and diinsertion derivatives is observed. The elimination reactions of (Et2GeO)nand (Et2GeS)3from these addition derivatives lead to corresponding carbon diazolidines.The mechanism of these addition‐elimination reactions is precised. The interest of these reactions in organic sy

ISSN:0018-019X    

DOI:10.1002/hlca.19760590406

出版商:WILEY‐VCH Verlag GmbH    

年代:1976

数据来源: WILEY

摘要:

Photoinduced Cycloadditions of 2,2‐Dimethyl‐3‐phenyl‐2H‐azirine with Nitriles and ‘push‐pull’ Olefines.Electron deficient nitriles of the type5a–ein contrast to nonactivated nitriles undergo regiospecific [2+3]cycloadditions to benzonitrile isopropylide (2b), which was generatedin situby irradiation of 2,2‐dimethyl‐3‐phenyl‐2H‐azirine (1b), to yield the 2H‐imidazole derivatives6a–e(Scheme 2). The structure of the photoproducts was mainly deduced from13C‐NMR. and mass spectrometry.Whereas normal olefins or enolethers do not react with2b, push‐pull olefins of the type10a–dreadily undergo the cycloaddition to give the 3‐alkoxy‐5,5‐dimethyl‐2‐phenyl‐1‐pyrrolines11a–d(Scheme 3 and 4). The structure of the photoproducts11a–dindicates that the regiospecificity of the cycloaddition corre

ISSN:0018-019X    

DOI:10.1002/hlca.19760590407

出版商:WILEY‐VCH Verlag GmbH    

年代:1976

数据来源: WILEY

摘要:

New methods for the preparation of 21‐fluoro‐steroids.21‐Fluoro‐20‐oxosteroids are obtained either by reacting a 21‐diazo‐20‐oxo‐steroid with hydrofluoric acid or by subjecting a 21‐mesyloxy‐20‐oxo‐steroid to reduction with the radical anion derived from lithium and biphenyl, followed by treatment of the resulting enolate

ISSN:0018-019X    

DOI:10.1002/hlca.19760590408

出版商:WILEY‐VCH Verlag GmbH    

年代:1976

数据来源: WILEY

摘要:

AbstractThe helium (I) photoelectron spectrum of C(CN)4curiously displays ionizations only in two small windows from 13.8 eV to 14.5 eV and from 14.8 eV to 15.5 eV, respectively. A tentative assignment of the numerous overlapping bands – based on a spectroscopically parametrized LCBO MO model – correlates satisfactorily with ionization potentials of other cyano compounds as well as of tetrahalometha

ISSN:0018-019X    

DOI:10.1002/hlca.19760590409

出版商:WILEY‐VCH Verlag GmbH    

年代:1976

数据来源: WILEY

摘要:

AbstractSeveral alkylbenzene‐TCNE complexes are reinvestigated, yielding improved ground state thermodynamic parameters. The effect of competing solvent complexation with the acceptor is also considered. The experimental CT‐band profiles for the complexes in solution and in the gas phase are deconvoluted into two (theoretically expected) CT‐subbands, furnishing accurate energies of the first and second CT‐state of the systems. Comparison with the corresponding donor IP's leads to insight into the preferred ground state conformation of the complexes. The thermodynamics of ionic photodissociation of the complexes is evaluated as a function of solvation and the results compared with recent experiment

ISSN:0018-019X    

DOI:10.1002/hlca.19760590410

出版商:WILEY‐VCH Verlag GmbH    

年代:1976

数据来源: WILEY

摘要:

AbstractThe synthesis of N‐methyl‐benz[f]isoindole (2) and N‐methyl‐dibenz[e,g]isoindole (3) is reported. The NMR. spectra of N‐methyl‐isoindole (1) and of2have been analysed and the implications concerning the alternation of bond lengths are discussed. The photophysical properties of1to3have been investigated by the following methods: HeI photoelectron (PE.) spectroscopy, UV./VIS. absorption (polarization measurements by the stretched‐foil technique) and emission spectroscopy (fluorescence spectra, lifetimes and quantum yields, phosphorescence spectra), and flash spectroscopy (triplet‐triplet absorption spectra). The discussion of the results is based on HMO. and PPP SCF CI. calculations and points to the relationship between the heterocycles1to3and the corresponding benzenoid hydrocarbons obtained by replacement of the NMesubunit by CHCH. Some comments concerning the ground state properties of isoindole and related compounds are derived from the analysis of t

ISSN:0018-019X    

DOI:10.1002/hlca.19760590411

出版商:WILEY‐VCH Verlag GmbH    

年代:1976

数据来源: WILEY