Mild and easy access to sapphyrins by electrochemical synthesis

Here we report the optimized synthesis of pentapyrroles. We succeeded in increasing the yield for pentapyrrole PPy 1a by heating at 100 [Formula: see text]C for 4.5 h. These conditions also allowed a greater increase in the yield for PPy 1c. In contrast, with PPy 1d and 1e possessing EDGs the formation of pentapyrroles was not observed. These pentapyrroles then allowed us to access sapphyrins (e.g. cyclic analogs of pentapyrroles) by electrosynthesis. The optimized conditions for obtaining the fluorinated sapphyrins 2a and 2b involve the addition of 10 mol% TBAI (tetra-n-butylammoniom iodide), 2 eq. of TFA in CHCl 3 . In comparison with classical organic synthesis, the amount of TFA was considerably reduced from 100 to 2 eq. and the oxidizing agent, [Formula: see text].[Formula: see text]. iodine, was continuously electrogenerated from the catalytic amount of TBAI used as a redox mediator.