Rk. Pandey et al., NEW SYNTHESES OF BILIVERDINS, CORROLES AND AZAPORPHYRINS FROM 1,19-DIBROMO-AC-BILADIENE SALTS, Journal of the Chemical Society. Perkin transactions. I, (8), 1994, pp. 971-977
Treatment of the readily available, 1.19 dibromo-ac-biladiene dihydrob
romide salts 3 with dimethyl sulfoxide (DMSO) in presence of a catalyt
ic amount of toluene-p-sulfonic acid affords symmetrical and unsymmetr
ical biliverdins 4 in excellent yield; unsymmetrically substituted 1.1
9 dibromo-ac-biladiene dihydrobromide 3c was prepared in a stepwise fa
shion via a tripyrrin salt. Under appropriate reaction conditions, the
ac-biladiene dihydrobromides were also converted in modest yields int
o the corroles 5 and the azaporphyrins 6.