Electron-rich olefins. 4. Electron-rich compounds with thiophosphinamide, carboxamide, O-silylurethane and O-silylisourea functionality. Synthesis, spectroscopy, chemical and electrochemical reactivity

, , und . Chemische Berichte 122 (5): 933--939 (1989)


N,N'-Disubstituted 1,4-dihydropyrazines I; R = CO2SiMe3, C(:NPh)OSiMe3, P(S)Me2, COMe were prepd. by reductive addn. to pyrazine or by insertion of CO2 or Ph isocyanate into the N-Si bonds of the N,N'-bis(trimethylsilyl) deriv. At room temp. 1H-NMR data show hindered rotation around the N-C(:X) single bonds in I R = CO2SiMe3, C(:NPh)OSiMe3, COMe but not in I R = P(S)Me2 or in the CONMe2 disubstituted compd. NMR shifts, colors, the oxidn. potentials from cyclic voltammetry, and reactivity towards air and TCNE illustrate that the electron-withdrawing capability increases in the substituent order SiR3 \textless CO2SiMe3 \textless C(:NPh)OSiMe3 $\approx$ P(S)Me2 \textless COMe. Notwithstanding, the N,N'-bis(thiophosphinyl) and the N,N'-diacetyl deriv. are easily converted to persistent radical cations whereas the O-silylated compds. are only irreversibly oxidized, albeit at very low potentials. on SciFinder(R)

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