However, variation of the imidazolopyrimidine component was less straightforward: the reactions of 6-bromoimidazo[1,2-a]pyrimidine with naphthalene and quinoxaline, and of unsubstituted imidazo[1,2-a]pyrimidine with naphthalene, were all significant lower yielding that the corresponding reactions of S9. Although dearomative photocycloadditions are known, the few examples that involve two aromatic substrates are either intramolecular or involve anthracene dimerisation. The viability of a [4+3] cycloadditionoxidation with such a range of diverse aromatic substrates was remarkable: