A two-step, one-pot route to swap the pyrroline moiety in meso-tetraaryldihydroxy-chlorins with an O/N-substituted oxazoline

Reaction of diolchlorin 1 with NaIO4/silica gel in the presence of a secondary amine or alcohol, followed by MnO4−-induced oxidation, leads to the replacement of a pyrroline β-carbon with oxygen to form α-substituted oxazolochlorin aminals or acetals 4, respectively.