The present invention provides a process of preparation of naphthochlorins and other chlorins with annelated ring systems useful for photodynamic therapy and the compounds themselves. The method for producing naphthochlorin compounds include contacting compounds such as meso-(2'-hydroxymethyl)phenyl porphyrin or meso-(2'-N,N,N-trialkylaminomethyl)phenyl porphyrin precursors with at least one acid catalyst at sufficient temperature for a sufficient time to yield the desired conversion. In a similar manner chlorins possessing annelated ring systems may be made from compounds such as meso-(2'-hydroxymethyl)aryl porphyrins or meso-(2'-N,N,N-trialkylaminomethyl)phenyl porphyrin. The procedures described herein provide new routes for synthesizing naphthochlorins and chlorins with annelated ring systems.