Free Base Porpholactone from meso-Tetraaryl-2 , 3-dihydroxy-chlorin

Abstract

meso-Tetraaryl-2,3-dihydroxychlorins (1) were converted in one step to the novel free base macrocycles meso-tetraaryl-2,3-dialkoxy-2a-oxa- 2a-homoporphyrins (morpholinochlorins, 3). Their bathochromically shifted chlorin-type UV−vis spectra indicate the presence of a nonplanar chromophore. The structure of meso-tetratolyldiethoxymorpholinochlorin (3b), as determined by X-ray crystallography, was found to be largely planar, suggesting significant conformational flexibility of these macrocycles. Oxidation of diol 1 with MnO4- generates known porpholactone 4 in high yields. Nature