New syntheses of biliverdins, corroles and azaporphyrins from 1,19-dibromo-ac-biladiene salts

Treatment of the readily available, 1,19 dibromo-ac-biladiene dihydrobromide salts 3 with dimethyl sulfoxide (DMSO) in presence of a catalytic amount of toluene-p-sulfonic acid affords symmetrical and unsymmetrical biliverdins 4 in excellent yield; unsymmetrically substituted 1,19 dibromo-ac-biladiene dihydrobromide 3c was prepared in a stepwise fashion via a tripyrrin salt. Under appropriate reaction conditions, the ac-biladiene dihydrobromides were also converted in modest yields into the corroles 5 and the azaporphyrins 6.