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  • 1990-1994  (3)
  • Organic Chemistry  (3)
  • Double resonance
  • 1
    Electronic Resource
    Electronic Resource
    Simultaneous Formation of 8H-Isoquino[2,1-b][2,7]naphthyridin-8-ones and 13H-Pyrido[4′,3′:3,4]pyrrolo[2,1-b][3]benzazepin-13-ones, a Novel Potential Alkaloidal System (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 155-163 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Condensation of 3,4-dihydro-6,7-dimethoxyisoquinoline (4) with 4-methylnicotinoyl chloride (12) in refluxing pyridine gives 5,6,13,13a-tetrahydro-2,3-dimethoxy-8H-isoquino[2,1-b][2,7] naphthyridin-8-one (11), along with some of its 13,13a-didehydro derivative 7. A similar reaction of 4 with 4-(chloromethyl)nicotinoyl chloride (14) affords, in addition to 7, the isomeric product 10,11-dihydro-7,8-dimethoxy-13H-pyrido[4′,3′:3,4]pyrrolo[2,1- b][3]benzazepin-13-one (3). Analogous pairs of products are obtained from 3,4-dihydro-6,7-(methylenedioxy)- and 3,4-dihydro-6,7,8-trimethoxy-isoquinolines (15 and 18, resp.). The structure of 3 was established by extensive NMR data and confirmed by single-crystal X-ray studies. Structure 7 has the ring system of the Alangium alkaloids like alangimarinc (1), while the isomeric ring system 3 is predicted to be present in nature on biogenetic reasoning.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770118
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis and Structure of η4-Enone Complexes of Ruthenium(0) (1993)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 76 (1993), S. 976-987 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A variety of [Ru(CO)2L(η4enone)] complexes (L = phosphines, phosphites, and arsines, enone = (E)-4-phenylbut-3-en-2-one) have been synthesized. 1H-, 13C-, and 31P-NMR spectra are reported and the X-ray structures of two Ru complexes with L = Ph3P(7), Et3P (10) and one Fe complex with L = Ph3P (14) are presented. All three compounds crystallize in the same monoclinic space group P21/n with a = 10.575(2) Å, b =9.213(2) Å, and c = 27.608(5) Å, β = 100.04(2)°, Z = 4 for 7, a = 10.276(3) Å, b = 12.935(3) Å, and c = 14.854(2) Å, β = 96.96(2)°, Z = 4 for 10, and a = 10.492(2) Å, b = 9.232(3) Å, and c = 27.129(3) Å, β = 98.67(2)°, Z = 4 for 14. The structures of the Ru complexes are compared with the Fe analogues. In the case of M = Ru and L = (EtO)3P, (MeO)3P, and (i-PrO)3P (9, 11, and 13, respectively) stereoisomers could be detected by 31P-NMR at room temperature, wich arise from rotation at the coordinated metal centre.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19930760220
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  • 3
    Electronic Resource
    Electronic Resource
    Electronic and Steric Influence of Axial and Equatorial Ligands in Vitamin B12 Model Complexes Derived from Cobaloxime: Electrochemical and 59Co-NMR StudiesTransition-Metal NMR Spectroscopy, Part XIV; Part XIII:[1], Presented in part at the ‘XIII International Conference on Organometallic Chemistry’, Torino, September 4-9, 1988. (1990)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 73 (1990), S. 1469-1480 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In four series of strictly related organocobalt complexes, derived from cobaloximes by replacement of the O…H…O with O…-BF2…O and/or (CH2)3 groups, the trends of 59Co-NMR shielding and electrochemical data are discussed. A largely parallel behaviour of the plots of E1/2(I) values for the first Co(III)/Co(II) electron transfer vs. the 59Co chemical shifts reflects the similar sensitivity of the two parameters to a change in electron affinity of the central metal ion due to a variation of the organic group R. E1/2(II) values for the second Co(II)/CO(I) electron transfer are less sensitive to the change of R, but the trend of the plot vs. δ(59Co) is still parallel in the four series. Consistent deviations from a roughly linear dependence of E1/2(I) on pKa of the hydrocarbon acid corresponding to R, on Taft constant s̰* and on 59Co shielding are noticed for the isopropyl derivatives and attributed to a steric effect. This was confirmed in a series of R—Co(DMG)pyridine complexes in which 59Co shielding decreases steadily with increasing steric parameter Es (Taft) of the alkyl group. There is experimental evidence from X-ray data that δ(59Co) decreases with an increase of the Co—C bond length, illustrating steric hindrance in alkyl coordination to be responsible for the decreased shielding of the 59Co nucleus. The relative displacements of the graphic displays for the different series reflect the effect of changes in electron affinity of the redox center, due to the equatorial ligand, which, in turn, is caused by variations in the electron-withdrawing power due to the introduction of the BF2 group and by the change from -2 to -1 valence of the (CH2)3-capped ligands.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19900730527
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