IMPROVED SYNTHESES OF 5,10,15,20-TETRAKISARYLPORPHYRINS AND 5,10,15,20-TETRAKISALKYLPORPHYRINS

Three significant modifications to existing methods for the preparatio n of the important 5,10,15,20-tetrakisarylporphyrins have improved iso lated yields, simplified work-up and made large-scale synthesis feasib le. Two tetrakisalkylporphyrins were also produced. A two-stage approa ch using hydrogen peroxide in acetic acid as second stage oxidant gave good yields but for ease of isolation and convenience in working on a large scale, the one-pot approach is preferred. No one method appears to be suitable for all such tetrakisarylporphyrins and, for best yiel ds, the method of preparation needs to be chosen carefully. Applicatio n of statistical optimisation techniques (factorial two design and sim plex operation) led to considerably enhanced yields for the one-pot me thod. For one of the two-stage modifications, significant amounts of c hlorins were observed, sometimes of such magnitude as to make it suita ble as a method for their preparation.