Cyclizations of terminally substituted a,c-biladiene salts to give meso-substituted porphyrins
Cyclizations of 1′,8′-disubstituted a,c-biladiene salts using copper(II) salts afford the corresponding meso-substituted porphyrins (after removal of copper) along with smaller amounts of the corresponding meso-unsubstituted analogues. For example, the a,c-biladiene salt (6) (1′-Me, 8′-Et) affords the corresponding meso-methylporphyrin (10) as the major product. The diethyl-a,c-biladiene (13) gave the meso-methylporphyrin (14). Copper(II) promoted cyclizations of an a,c-biladiene (17) substituted at the 1′ and 8′ positions with propionic ester groups gives mainly the meso-acrylic substituted porphyrin (18) after demetallation. The 1′-unsubstituted-8′-propionic ester a,c-biladiene salt (25), when cyclized using iodine-bromine in hot o-dichlorobenzene gives the meso-acetic substituted porphyrin (28), indicating that such a transformation might provide a viable route for synthesis of chlorophyll-a derivatives.
Publication Source (Journal or Book title)
Journal of the Chemical Society, Perkin Transactions 1
Smith, K., & Pandey, R. (1987). Cyclizations of terminally substituted a,c-biladiene salts to give meso-substituted porphyrins. Journal of the Chemical Society, Perkin Transactions 1, 1229-1236. https://doi.org/10.1039/p19870001229