Improvements are described to the synthesis of the catalytically important 5,10,15,20-tetrakis(2,6-dichlorophenyl) porphyrin 1 (R = H) and [2,3,7,8,12,13,17,18-octachloro-tetrakis(2,6-dichlorophenyl) porphyrinato]manganese(III) 3 (R = CI) which enable large-scale preparation of such compounds to be carried out easily. A comparative study of the catalytic performance of the manganese complexes of these two porphyrins proved that, contrary to earlier expectations, the manganese complex of 5,10,1 5,20-tetrakis(2,6-dichlorophenyl)porphyrin is the most stable and efficient catalyst for epoxidation when using sodium hypochlorite as oxidant. With [2,3,7,8,1 2,1 3,1 7,18-octachloro-tetrakis(2,6-dichlorophenyl)porphyrinato]manganese(III) 3, chlorinated products tend to be formed and these can be the dominant products for some substrates.