Synthesis of Unsymmetrical Heterobenzisapphyrins.

Two examples of highly unsymmetrical heterobenzisapphyrins containing one benzene, two pyrroles, one furan, and one thiophene ring connected via four meso-carbons and one direct bond were prepared over a sequence of five steps in 8-9% yields. The X-ray structure revealed that the furan ring was inverted from the macrocyclic framework and the macrocycle was nearly planar. Spectral and electrochemical studies indicated that the macrocycle was nonaromatic in nature due to lack of conjugation.