Synthesis of 3,7-dihydroimidazo[1,2a]pyrazine-3-ones and their chemiluminescent properties

A series of 3,7-dihydroimidazo[1,2a]pyrazine-3-ones were prepared from 2-amino-3,5-dibromopyrazine. The concise synthesis of coelenterazine (), in three steps, 48% overall yield and >99% purity exemplifies the strategy. Further, the synthetic approach facilitated the regiospecific incorporation of carboxyalkyl linkers on the 3,7-dihydroimidazo[1,2a]pyrazine-3-one nucleus that are required for bioconjugation. Peroxymonocarbonate, an electrophilic oxidant, was used to initiate ‘pseudo-flash’ chemiluminescence from this class of molecules.