Formylporphyrins were prepared by using either the 1,3-dithian-2-yl residue as a precursor for the CHO group or by the Vilsmeier reaction. Two synthetic routes for the introduction of the 1,2-dithian-2-yl group were explored. Furthermore, reactions of the 1,3,5-trithian-2-yl group with porphyrins were examined as well as spirobisdithiane derivatives as precursors for the ultimate assembly of porphyrin spirobisdithanyl-linked bioconjugates. The obtained formylporphyrins were reacted with organomagnesium or organophosphorus compounds. A series of hydroxyporphyrins resulting from the Grignard reaction of 5,15-substituted porphyrins were synthesised in high yields. Several porphyrins with unsaturated residues introduced by the Wittig reaction were obtained in moderate yields. The less sterically hindered 5,15-substituted porphyrins show increased reactivity and give higher yields; their reaction products are higher in stability relative to other porphyrin systems.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)