摘要:

Radical Ions of Bridged [14] Annulenes. Investigations on the Influence of Frontier Orbitals on Reactivity and BondingThe radical anions and the radical cations derived fromtrans‐15, 16‐dimethyl‐1, 4:8,11‐ethandiyliden[14]annulene (6),trans‐15‐methyl‐1,4:8,11‐ethandiyliden[14]annulene (7) andcis‐15, 16‐propano‐1,4:8,11‐ethandiyliden[14]annulene (8) are described. The hyperfine data of the radical anions6, 7and8resemble those of the structurally related radical anions oftrans‐10b, 10c‐dimethyldihydropyrene (4) andtrans‐10b, 10c‐dihydropyrene (5). This finding leads to the conclusion, that the change in the relative arragement of the saturated bridge within the fourteen‐membered π‐perimeter by passing from4 (5)to6(7, 8) does not in fluence the energetic sequence of the lowest unoccupied molecular orbitals. The behavior of6and7towards oxidation parallels the photochemical reactivity of4. The hyperfine coupling constants of the radical cations derived from6and7indicate that the removal of an electron is accompanied by an isomerization of the molecular framework. The investigation of the electron transfer process gby cyclic voltammetry supports these findings. The radical cations prefer the cyclophane‐like structures6aand7a, in which the centr

ISSN:0018-019X    

DOI:10.1002/hlca.19840670302

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractThe He(Ia) photoelectron (PE) spectra of the (E,E)‐, (E,Z)‐ and (Z,Z)‐isomers of the title compound have been recorded to obtain information about their conformation in the gas phase. For a valid correlation with the PE data of other dienes it is necessary to take the potentialsV(φ) for internal rotation and the corresponding conformer population densities P (φ) into account, as well as the rather complicated way wy in which the π−1ionization energy gap ΔI(φ) depends on the direct π‐orbital interaction and the long‐range ‘through‐space’ interaction between the semi‐localized methyl‐group orbitals and the π‐orbitals. These factors being taken into account, the mean twist angles,φ, compatible with the PE‐spectroscopic results areφ(E,E) ≈︁ O° ± 30°,φ(E,Z) ≈︁ 80° or 110° within ± 15°, andφ(Z,Z) ≈︁ 85° to 105°. These results are in rough agreement with electron diffraction data byTraetteberg[15], other spectroscopic results and, for the (E, E)‐ and (Z,Z)‐isomers, internal rotation potentialsV(φ) previously calculated byRoth[17]. On the other hand the potentialV(φ) proposed for th

ISSN:0018-019X    

DOI:10.1002/hlca.19840670303

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractThe title cation ( = Ni2L +3) is formed in a variety of reactions (Schemes 1and2) in systems containing Ni2+and (2‐thiolatoethyl)‐diphenylphosphine (= L−) in the absence of coordinating anions at Ni2+/L−ratios>0.5 in apolar or moderately polar media. Solid [Ni2L3]CIO4and [Ni2L3]BPh4have been isolated.Job's plots confirm the Ni2L +3‐ stoichiometry in solution.31P‐NMR data are consistent with ≥ 97% Ni2L +3(vs.⩽ 3% of hypothetical Ni3L 2+4) at equilibrium and support the suggested configuration (Fig. 2). The equilibrium between NiL2+ NiL2Br2and Ni2L +3+ Br−varies with the solvent composition in CH23Cl2/EtOH mixtures. The rate of formation of Ni2L2Br2from Ni2L +3and bromide (in high excess) in CH2Cl2is first‐order in [Ni2L +3]totbut depends on the ratio [Bu4NBr]tot/[Ni2L3· ClO4]tot, even at a high excess of bromide. This is interpreted by efficient competition in ion‐aggregate formation between the small perchlorate concentration introduced as the counterion of Ni2L

ISSN:0018-019X    

DOI:10.1002/hlca.19840670304

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractThe photochemical behaviour of the title compound1ais compared to that of the non‐fluorinated parent ketone 2‐methylcyclohexanone (1b). Substitution of the CH3‐ group on C(2) by a trifluoromethyl group strongly enhances2H‐ andRH‐ reduction product formation in cyclohexane or 2‐propanol and oxetane formation in the presence of 2‐methylpropene as olefinic component. Under all these conditions1bexclusively undergoesa‐cleavage, a process observed for1aonly in non‐reducing solvents as benzene ort

ISSN:0018-019X    

DOI:10.1002/hlca.19840670305

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractThe olefins2, 7, 11, and19, have been reduced using catalytic amounts of cob(I)alamin(I(I)). During a slow saturation, the catalyst is able to differentiate the two diastereotopic faces of the endocyclic double bonds in11(t1/24 h,.cf. Scheme 3) are reduced much faster. A rationalization of the data can be obtained formulating tertiary alkylcobalamins as intermediates. Of the oxime6(cf. Scheme 2) and thep‐ bromobenzoate23(cf. Scheme 5) the structures have been determined by X‐ray analy

ISSN:0018-019X    

DOI:10.1002/hlca.19840670306

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractCob(I) alamin (1(I))‐catalyzed reduction of the aldehyde2led to the two crystalline cyclopropanols3and4(seeScheme 2). The protolytic ring‐opening starting from3produced the saturated aldehydes6and7;8was formed in traces only (seeScheme 3). The protolysis starting from3led, therefore, mainly to retention of configuration at the spiro C‐atom (7); ring‐opening with inversion was observed in traces only (8). Starting from4, the protolysis produced9and7; the absence of8showed this protolysis to proceed9and7; the absence of8showed this protolysis to proceed exclusively with inversion of configuration at the spiro center. Of thep‐bromobenzoate5(cf. Scheme 2) the structure has been determined by X‐r

ISSN:0018-019X    

DOI:10.1002/hlca.19840670307

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractThe absolute configuration of dechlorogilmaniellin (2) could be determined from its chiroptical data by applying coupled‐oscillator theory to the CD couplet around 272 nm and from the sign of its n →π*Cottoneffect. Gilmaniellin (1) has the same absolute configura

ISSN:0018-019X    

DOI:10.1002/hlca.19840670308

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

Structural Elucidation of Niphimycin, Part 3. Identity of Scopafungin and Niphimycin I. Position of the Malonyl Residue of Niphimycin and CopiamycinThe identity of scopafungin with niphimycin I was proven by spectroscopic and chromatographic methods and by common degradation products. The position of the malonyl residue in niphimycin I (9) and in copiamycin (14) was deduced by1H‐NMR spin‐decoupling experiments of a degradation product (

ISSN:0018-019X    

DOI:10.1002/hlca.19840670309

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractThe conformational behaviour of metoclopramide, a neuroleptic benzamide, and model compounds was investigated byt1H‐NMR spectroscopy. An intramolecular amide‐methoxy H‐bond is shown to exist in CDCl3‐solution, but not in D2O‐solution, independently of the length and protonation state of the basic side‐chain. This H‐bond creates a virtual cycle which may be a key feature for the binding of neuroleptic benzamides to the dopamine receptor. The conformational behaviour of the aminoethyl side‐chain is shown to be markedly condition‐dependent. For metoclopramide and its analogues in their protonated form, thegauche‐ andtrans‐ rotamers have identical energies in D2O‐as well as in CDCl3‐solutins. For the non‐protonated molecules, thetrans‐rotamer is favoured in D2O‐solutin, while thegauche‐rotamer is favoured in CDCl3‐solution (ΔG°≃|0.5|kcal/mol in both cases). The side‐chain conformation of neuroleptic benzamides i

ISSN:0018-019X    

DOI:10.1002/hlca.19840670310

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractThe solvolysis rates and products of the 2‐exo‐ norbornyl, bicyclo[3.2.1]oct‐8‐yl, bicyclo[3.3.1]non‐2‐yl, bicyclo[3.2.1]oct‐6‐yl, bicyclo[3.2.1]oct‐2‐yl and bicyclo[3.2.2]non‐6‐ylp‐toluenesulfonates10–15, respectively, are reported. Theexo/endorate ratios for these epimeric secondary tosylates in 80% EtOH varied from 1125 for11to 1.6 for15. The relative rates varied between 2278 forexo‐10and 4 ·10−3forendo‐11. The hydrolysis products were mainly rearranged alcohols and olefins. The unrearranged alcohols from theexo‐tosylates were formed with complete or predominant retention of configuration, whereas those derived from theendo‐tosylates were mostly inverted. These results confirm the hypothesis that relative rates, as well as products, are largely determined by the degree of bridging between the cationic center and a dorsal C‐atom in the transition state and in the resulting ion pairs. Since bridging is a directed bonding interaction, it is subject to the same angle and conformational strains as ordinary covalent bonds. But bridging requires less geometrical change than the formation

ISSN:0018-019X    

DOI:10.1002/hlca.19840670311

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY