Conjugated macrocycles related to the porphyrins. 25. Proton NMR spectroscopic evidence for a preferred [18]annulene substructure in carbaporphyrins from the magnitude of selected 4JH,H CH=C-CH3 coupling constants

Article abstract of DOI:10.1021/jo020703u

Two new benzocarbaporphyrins with four or five alkyl substituents have been synthesized by the "3 + 1" MacDonald methodology. At lower temperatures, the proton NMR spectrum of the asymmetrically substituted carbaporphyrin 8 gave two NH resonances, while c