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The condensation of biladiene-a,c dihydrobromides with benzaldehyde gives 5-phenylporphyrins. The reaction conditions have been studied and optimized; it is shown that synthesis of biladiene-a,c dihydrobromides can be combined with their following condensation with benzaldehyde.

Study on the nitration of phenyl-substituted porphyrins showed that protonation of the porphyrin macroring does not affect the relative reactivity of the meso-and β-positions and phenyl groups. * For communication II, see [1].Like other aromatic compounds possessing a closed conjugated π-electron system, porphyrins are capable of reacting with electrophiles to give the corresponding substitution products. The most interesting and widely known electrophilic substitution reaction is nitration. Nitration of compounds of the porphyrin series was reported for the first time in [2][3][4]. As a result, mesonitro derivatives were isolated even in reactions with porphyrins having no substituents in the β-positions. Treatment of porphyrin (I) with a nitrating mixture gives meso-nitroporphyrin (II), and further nitration of the latter yields 5,10-dinitroporphyrin (III) [5]. A mixture of meso-nitro derivatives V-VIII was obtained by nitration of octaethylporphyrin IV [6,7]. First attempts to perform electrophilic nitration of meso-tetraphenylporphyrin IX were unsuccessful. Treatment of IX with a nitrating mixture over a period of 9.5 h resulted in the formation of dihydroxyporphodimethene X, presumably through intermediate ipso-nitration product XI [8] (Scheme 1). Kruper et al. [9] succeeded in nitrating compound IX by treatment of its solution in methylene chloride or chloroform with fuming nitric acid (d = 1.53 g/cm 3 ). The nitration occurred at the para-position of one of phenyl substituents and afforded 5-(4-nitrophenyl)-10,15,20-triphenylporphyrin (XII) (Scheme 2). Further nitration (by increasing the amount of nitrating agent) led to the formation of a 2 : 1 mixture of isomeric 5,10-and 5,15-bis(4-nitrophenyl)-porphyrins XIII and XIV. Prolonged nitration gave 5,10,15-tris(4-nitrophenyl)-20-phenylporphyrin (XV). The nitration of compound IX and its derivatives with various nitrating agents was studied in detail in [10][11][12]. On the basis of the obtained results it was concluded that meso-and β-positions in meso-phenylporphyrins are deactivated toward electrophilic substitution owing to protonation of the inner nitrogen atoms [12]. Compound XVI was not isolated.The goal of the present study was to compare the reactivity of the meso-and β-positions in the porphyrin

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