摘要:

AbstractThe methylene‐blue sensitized photooxygenation of heptamethylCoα,Coβ‐dicyanocobyrinate (1, cobester) atca.−45° and in (D3)acetonitrile solution proceeds readily to the stage of selective double cleavage of the corrin macrocycle. It furnishes the bisected heptamethylCoα,Coβ‐dicyano‐5,6:14,15‐tetraoxo‐5,6:14,15‐disecocobyrinate (3) in 91% yield after warming the photooxygenation mixture to room temperature. Complex3is also obtained by photooxygenation of the secocorrinoid oxygenation products of1, namely of heptamethylCoα,Coβ‐dicyano‐5,6‐dioxo‐5,6‐secocobyrinate (2a) and of its isomer heptamethylCoα,Coβ‐dicyano‐14,15‐dioxo‐14,15‐secocobyrinate (2b). When the raw photooxygenation product of1is kept at low temperature,3is not formed in a significant amount; spectral analysis reveals4as intermediate that is transformed into3quantitatively upon warm‐up and storage at r.t. Compound4is assigned the structure of heptamethylCoα,Coβ‐dicyano‐5,6‐epidioxy‐5,6‐dihydro‐14,15‐dioxo‐14,15‐secocobyrinate, based on NMR‐spectral data and since4is also formed cleanly in the corresponding low‐temperature photooxygenation of2b. Catalytic reduction of the Co(III) complex3(H2, Pt/C) in the presence of EDTA produces a colourless oil, from which the bicyclic fragments5(corresponding to rings A and D of1) and6(corresponding to rings B and C of1) are obtain

ISSN:0018-019X    

DOI:10.1002/hlca.19850680502

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractOn flash vaccum thermolysis at temperatures between 390 and 585°, the epoxyenones1–9and the epoxydienes10–12undergo various types of reactions involving CC and/or CO bond cleavage in the oxirane ring. Thus, the compounds1,4–9,11, and12were transformed to the divinyl ethers13,20,21,24,25,29, and38by a reversible [1,5] homosigmatropic H‐shift. On thermolysis of the epoxides1–12, several products formedviacarbonyl‐ylide intermediates were also isolated. The extent of the formation of ylide products is clearly related to the conjugating ability of the functional groups neighboring the oxirane. Thus, the epoxides3,5, and7–10, bearing a C(3)C(4) bond, a 5‐oxo function, a 3,4‐epoxy or a 3,4‐methano group, preferentially underwent reactionsviaa carbonyl‐ylide intermediate. As a further reaction pathway, the epoxides1–12undergo cleavage of the C–O bonds of the oxirane, which, however, is presumably an acid‐cataly

ISSN:0018-019X    

DOI:10.1002/hlca.19850680503

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractThermolysis of 5,6‐epimino‐5,6‐dihydro‐β‐ionone (1) and itsN‐methyl derivative (2) leads to their monocyclic isomers6and10, respectively, presumably due to a direct [1,5]‐H shift; on prolonged heating, these isomers are converted easily into pyrrole derivatives. In contrast, the thermoisomer12resulting from 5,6‐(N‐methoxycarbonyl)epimino‐5,6‐dihydro‐β‐ionone (3) by the same mechanism, does not undergo further ring transformation, but equilibrates with

ISSN:0018-019X    

DOI:10.1002/hlca.19850680504

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractIt is predicted by MINDO/3 calculations that the 1,5‐trishomobarrelenediyl dication4would be as much stabilized over the bicyclo[2.2.2]octanediyl dication3as the monocation7‐H is energetically favored over the hypothetical 1‐bicyclo[2.2.2]octyl10‐H. In spite of this, the bridgehead cations generated from the 1,5‐dihalo‐trishomobarrelenes6‐F,6‐Cl,6‐Br, and6‐I and from the 1,5‐diol6‐OH under long‐lived ion conditions were only the 5‐substituted monocations7‐F,7‐Cl,7‐Br,7‐I, and7‐OH, respectively, unequivocally identified by their1H‐ and13C‐NMR spectra as well as quenching products. Although there is efficient charge delocalization in7‐X, as revealed by the13C‐chemical shifts, the lack of formation of the bridgehead bridgehead dication4is not due to an unforeseen destabilization by the three α‐annellated cyclopropyl groups. Even the 1,5‐dichlorotetracyclo[3.3.2.02,4.06,8]decanes17‐Cl2and19‐Cl2and 1,5‐dichlorotricyclo[3.2.2.02,4]nonane12‐Cl2with only two and one α‐cyclopropyl groups, respectively, gave

ISSN:0018-019X    

DOI:10.1002/hlca.19850680505

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractMethyl 2‐allyl‐3‐oxo‐2,3‐dihydrothiophene‐2‐carboxylate (2) photocyclizes selectively to methyl 2‐oxo‐7‐thiatricyclo[3.2.1.03,6]octane‐1‐carboxylate (4). In contrast, 4‐thia‐2‐cyclohexenone3, on irradiation, affords only low yields of dimers, cycloadducts (2‐methylpropene) or

ISSN:0018-019X    

DOI:10.1002/hlca.19850680506

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

Diels‐AlderReactions with Activated 4‐Methyl‐1,3‐pentadienesEthyl 4‐methyl‐1,3‐pentadienyl ether, trimethyl[(4‐methyl‐1,3‐pentadienyl)oxy]silane, and 1‐(4‐methyl‐1,3‐pentadienyl)pyrrolidine and the corresponding piperidine analogue have been used inDiels‐Alderreactions with acrylonitrile, ethyl acetylenedicarboxylate, maleic anhydride, an

ISSN:0018-019X    

DOI:10.1002/hlca.19850680507

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractThe didehydro[n]annulenes1(n = 14),2(n = 18), and3(n = 22) are oxidized to radical cations. Reduction of the title compounds leads to radical anions and, in the case of2and3, to radical trianions. The hyperfine data of the paramagnetic derivatives are rationalized in terms of the occupation of n‐membered (n = 14, 18, 22) π‐perimeter MO's (HOMO, LUMO, NLUMO). The contact‐ion pairs of the radical anions show unexpectedly large alkali‐metal coupling c

ISSN:0018-019X    

DOI:10.1002/hlca.19850680508

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

Investigation of the Carotenoid Composition in the Petals of a Garden HybridNarcissus cvv‘Golden Harvest’The carotenoid composition of the petals of a yellow garden hybridDaffodilis reported. As major compound (all‐E)‐lutein was isolated. As minor compounds phytoene, phytofluene, (all‐E)‐β‐carotene, (9Z)‐lutein, (9′Z)‐lutein, (13Z)‐lutein, violaxanthin, and luteoxanthin were identified. The position of the (Z)‐double bond of the different isomers of lutein could be prov

ISSN:0018-019X    

DOI:10.1002/hlca.19850680509

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractDerivatives of the unknown 2‐amino‐6H‐1,3‐oxazin‐6‐one2have been synthesized for the first time in two steps and in excellent yields, starting fromN‐cyanocarbonimidates3a–cand cyanoacetates. The structures of2a–care assigned by NMR‐spectroscopic methods and corroborated by an X‐ray st

ISSN:0018-019X    

DOI:10.1002/hlca.19850680510

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractThe isotopic exchange between hydrogen and methane over Ni catalyst has been studied as a function of temperature, isotopic substitution, and ratio of hydrogen to methane. The experimental results can be described by means of a model in which methane is adsorbed either as methyl or as methylene. The adsorbed species undergo one or several exchanges. The four required parameters are adjusted to the experimental results. The exchange of partially deuterated methane with H2or D2allowed us to study the isotopic effect on the adsorption and the exchange processes.

ISSN:0018-019X    

DOI:10.1002/hlca.19850680511

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY