Two distinct approaches have been developed for the synthesis of chlorins bearing formyl groups: (1) reaction of an acetal-substituted 1-acyldipyrromethane with 2,3,5,6-tetrahydro-1,3,3-trimethyldipyrrin to give upon hydrolysis a 5-formylchlorin and (2) Pd-mediated coupling of a bromochlorin with a one-carbon synthon (hydroxymethyl tributyltin or CO) to give a 13-, 15-, or 3,13-formylchlorin. The zinc chlorins exhibit long-wavelength peak absorption maxima ranging from 626 to 667 nm, indicating the wavelength tunability afforded by formyl substitution.
Two distinct approaches have been developed for the synthesis of chlorins bearing formyl groups: (1) reaction of an acetal-substituted 1-acyldipyrromethane with 2,3,5,6-tetrahydro-1,3,3-trimethyldipyrrin to give upon hydrolysis a 5-formylchlorin and (2) Pd-mediated coupling of a bromochlorin with a one-carbon synthon (hydroxymethyl tributyltin or CO) to give a 13-, 15-, or 3,13-formylchlorin. The zinc chlorins exhibit long-wavelength peak absorption maxima ranging from 626 to 667 nm, indicating the wavelength tunability afforded by formyl substitution.