On the vinyl group photooxygenation of bilirubin-like model compounds

The photooxygenation of z-3-vinyl-4-methyl-5-(phenylmethylidene)-3-pyrrolin-2-one (1) and z-5′-oxo-4′-viny1–4-ethyl-3′,3,5-trimethyl-1′,5′-dihydro(2,2′)dipyrromethene (2) reveals no reaction at the vinyl groups; hence, none is expected at the vinyl groups of bilirubin IXα, and none has been found.