Synthesis and Characterization of Derivatized Capped Porphyrins
Tang, H., Wijesekera, T., and David Dolphin
Can. J. Chem.
Porphyrins I (R = H, NHAc, n = 1, 2) were prepared. C6H4(CHO)2-p was converted to RC6H3[(CHn)+2CO2H]2-p (R = H, NO2) using standard methods. The diacid chlorides were used to acylate two equivalents of a β-unsubstituted pyrrole, and the oxo groups were reduced by diborane. Following the transformation of the nitro function to the acetamide, appropriate modifications of the Et ester functions afforded the key bisformylpyrroles II. The cyanoacrylate-protected formylpyrrole derivatives were monochlorinated at the α-Me groups and condensed with two equivalents of an α-unsubstituted pyrrole to give the dipyrromethane dimers. Strong aqueous alkali caused saponification of the two ester groups and deprotection of the formyl functions to produce the unprotected dipyrromethane dimer, which, after thermal decarboxylation, was cyclized intramolecularly in acidic medium to give I.