Unusual sensitivity to the concentration of ethanol in the boron trifluoride/ethanol‐catalyzed synthesis of 5,10,15,20‐tetrakis‐(4‐cyano‐2,6‐dimethylphenyl)porphyrin by the lindsey method

The boron trifluoride/ethanol‐catalyzed condensation of 4‐cyano‐2,6‐dtmethylbenzaldehyde 1b with pyrrole by the Lindsey method to give the new, ortho ‐disubstituted 5,10,15,20‐tetrakis(4‐cyano‐2,6‐dimethylphenyl)porphyrin 2 was found to be highly sensitive to the concentration of ethanol. In the absence of ethanol the yield of porphyrin is only 1%. Yields can be increased to 20–25% with ethanol concentrations of 0.05–0.1% (v/v) but they decrease rapidly at higher concentrations of ethanol. Optimized procedures for the preparation of both 1b and 2 are described and the newly synthesized molecules are characterized by nmr ( 1 H and 13 C), mass spectra and elemental analysis.