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
作者:Anura Wickramasinghe、Laurent Jaquinod、Daniel J Nurco、Kevin M Smith
DOI:10.1016/s0040-4020(01)00329-5
日期:2001.5
Vilsmeier formylation of 5-substituted 1,9-diunsubstituted dipyrromethanes afforded 1,9-diformyldipyrromethanes in good yields. Their MacDonald condensation with tetra-beta -alkyldipyrromethanes produced 5,12,13,17,18-pentasubstituted porphyrins. A mesoelectron-donating group, presumably acting by destabilizing the porphyrin at, ground state, directs the nitrations to the mese-carbons. beta -Nitration takes place on porphyrins bearing a meso-electron-withdrawing group. Unhindered beta -nitro groups are shown to exert stronger electronic effects relative to meso-nitro groups by conjugating effectively with the porphyrin macrocycle. (C) 2001 Elsevier Science Ltd. All rights reserved.