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.