Synthesis and structural assignment of 2,4′-disubstituted benzylidenefluorenes and 4′-substituted benzylidene-1-azafluorenes
In the course of a study aimed at the investigation of edge-to-face arene-arene interactions, substituted benzylidenefluorenes 8-16 and benzylidene-1-azafluorenes 20-24 were synthesized as mixtures of E-Z-isomers. The full structural assignment of these compounds, performed by 2D NMR experiments, is described together with a study of their E-Z isomerization under equilibrating conditions. For compounds 8-16 no correlation was observed between the electron-donating or electron-withdrawing nature of the substituent groups and the E/Z equilibrium ratios. In the case of 20-24 the predominance of the E-isomers seems to depend exclusively on the N-lone pair-benzylidene ring electronic repulsion rather than on the nature of the para substituent on the aromatic ring.
Annunziata, Rita,Molteni, Valentina,Raimondi, Laura
p. 520 - 528
(2007/10/03)
9-ARYLIDENE-1-AZAFLUORENES
In the condensation of 1-azafluorene with aromatic aldehydes having electron-donating or electron-withdrawing substituents in the benzene ring the Z and E isomers of 9-arylidene-1-azafluorene are formed.It is suggested that the Z isomers exist in the form
Prostakov, N. S.,Fedorov, V. O.,Soldatenkov, A. T.
p. 2031 - 2033
(2007/10/02)
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