A non-tetradecarboxylative synthesis of 2,7,12,17-tetraphenylporphycene

A new synthetic method for 2,7,12,17-tetraphenylporphycene (2e, TPPo) which avoids tetradecarboxylation by sublimation of the intermediate tetracarboxylic acid 8 is reported. Thus, the use of a pyrrol 13a bearing two orthogonal ester groups allows the synthesis of bipyrrol 12a, from which the benzyl ester groups are selectively removed to afford diester 11. The latter is transformed to dialdehyde 10 by using the McFayden-Stevens reaction, thus avoiding the unstable bipyrrol 9 formed during the tetradecarboxylation of 8.