THE EFFECT OF ELECTRON-DONATING AND ELECTRON-WITHDRAWING SUBSTITUENTSON H-1-NMR AND C-13-NMR CHEMICAL-SHIFTS OF NOVEL 7'-ARYL-SUBSTITUTED 7'-APO-BETA-CAROTENES
Es. Hand et al., THE EFFECT OF ELECTRON-DONATING AND ELECTRON-WITHDRAWING SUBSTITUENTSON H-1-NMR AND C-13-NMR CHEMICAL-SHIFTS OF NOVEL 7'-ARYL-SUBSTITUTED 7'-APO-BETA-CAROTENES, Helvetica Chimica Acta, 76(5), 1993, pp. 1928-1938
The synthesis of 7'-aryl-7'-apo-beta-carotenes, where aryl (Ar) is Ph,
4-NO2C6H4, 4-MeOC6H4, 4-(MeO2C)C6H4, C6F5, and 2,4,6-Me3C6H2, is desc
ribed. NMR Chemical shifts of all H- and C-atoms are presented, togeth
er with specific examples of the spectra. In contrast to H-1 chemical
shifts which, except for H-C(8') and H-C(7'), did not differ greatly f
rom those of beta,beta-carotene, considerable variations in C-13 chemi
cal shifts were observed. Signals of the C(alpha) atoms of the polyene
chain [C(beta)=C(alpha)]n Ar were shielded, those of the C(beta) atom
s were deshielded, with some exceptions when n = 1; the effects decrea
sed with increasing n.