Investigation of complementary reactions of a dipyrromethanemonocarbinol with a dipyrromethane leading to a 5-isocorrole

ORGN 719

G. Richard Geier III, ggeier@mail.colgate.edu, Andrew C. Long, Rachel L. Fowler, Danette L. Flint, and Anna Y. O'Brien. Department of Chemistry, Colgate University, 13 Oak Drive, Hamilton, NY 13346
Complementary reactions of a dipyrromethanemonocarbinol with a dipyrromethane leading to a 5-isocorrole were investigated. 5-Isocorrole (pseudocorrole) is a porphyrinic macrocycle possessing a sp3 hybridized meso-position and a direct bipyrrole linkage. Analytical-scale reactions were performed to explore the interplay of acid catalyst, acid concentration, and reaction time on the yield of 5-isocorrole and the product obtained from self-condensation of the dipyrromethanemonocarbinol (a porphyrin or a porphodimethene). Representative conditions were examined via time course experiments. The complementary reaction routes led to very different outcomes. One route provided the 5-isocorrole as the major macrocyclic product with only low levels of porphyrin (from self-condensation). In contrast, the complementary route predominately afforded a porphodimethene (from self-condensation) and little 5-isocorrole. The selection of reaction route can have a profound effect on the outcome of the reaction. Key to this work was the preparation of the required dipyrromethane species and the development of methodology for monitoring analytical-scale reactions.