Improved syntheses of 5,10,15,20-tetrakisaryl- and tetrakisalkylporphyrins

Article abstract of DOI:10.3987/com-96-7436

Three significant modifications to existing methods for the preparation of the important 5,10,15,20-tetrakisarylporphyrins have improved isolated yields, simplified work-up and made large-scale synthesis feasible. Two tetrakisalkylporphyrins were also produced. A two-stage approach 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 yields, the method of preparation needs to be chosen carefully. Application of statistical optimisation techniques (factorial two design and simplex operation) led to considerably enhanced yields for the one-pot method. For one of the two-stage modifications, significant amounts of chlorins were observed, sometimes of such magnitude as to make it suitable as a method for their preparation.