Highly Fluorescent Dyes, Never Mind the Heavy Atoms

Significance

The carboselenation reaction of the 1,2-selenaplatinacycle 1 with dimethyl acetylenedicarboxylate (DMAD) affords a rigid 3-methylene-2,3-dihydroselenophene 2 in good yield. Alternatively, bis(9-dibenzobarrelenyl) diselenide (or disulfide) 3 can be reacted with DMAD in the presence of a palladium catalyst [or stoichiometric amount of Pd(PPh₃)₄] to produce 2 (or 4). The reaction is expected to proceed via analogous palladacycle 5, and the yield of 2 based on the recovered starting material was similar to that obtained in the reaction of platinacycle 1.