Synthesis of regiospecifically meso-functionalized tetraarylporphyrins via arylbis(2-pyrrolyl)methanes

This paper describes the synthesis of three new porphyrins 1-3 of alternate A(2)B(2) structure, by condensation of arylbis(2-pyrrolyl)methanes and arylaldehydes bearing suitable reactive substituents for further synthetic manipulations. This synthetic approach allows to place the reactive groups selectively on the 5,15 meso-aryls. The new porphyrins feature an ortho-nitro group in the case of 1 and a protected para-ethynyl group in compounds 2 and 3. Porphyrin 1, after reduction of the nitro group, is a useful intermediate for the preparation of cage or regiospecifically bis-tailed porphyrins. Compounds 2 and 3, after deprotection and Glaser-Hay coupling, should give linear polymers (molecular wires) suitable for electron-transfer and light-harvesting processes.