Investigations on the directive effects of a single meso-substituent via nitration of 5,12,13,17,18-pentasubstituted porphyrins: Syntheses of conjugated β-nitroporphyrins
Vilsmeier formylation of 5-substituted 1,9-diunsubstituted dipyrromethanes afforded 1,9-diformyldipyrromethanes in good yields. Their MacDonald condensation with tetra-β-alkyldipyrromethanes produced 5,12,13,17,18-pentasubstituted porphyrins. A meso-electron-donating group, presumably acting by destabilizing the porphyrin a2u ground state, directs the nitrations to the meso-carbons. β-Nitration takes place on porphyrins bearing a meso-electron-withdrawing group. Unhindered β-nitro groups are shown to exert stronger electronic effects relative to meso-nitro groups by conjugating effectively with the porphyrin macrocycle. © 2001 Elsevier Science Ltd.
Publication Source (Journal or Book title)
Wickramasinghe, A., Jaquinod, L., Nurco, D., & Smith, K. (2001). Investigations on the directive effects of a single meso-substituent via nitration of 5,12,13,17,18-pentasubstituted porphyrins: Syntheses of conjugated β-nitroporphyrins. Tetrahedron, 57 (20), 4261-4269. https://doi.org/10.1016/S0040-4020(01)00329-5