CHEMILUMINESCENCE OF THE LABILE 1,2-DIOXETANES AND EPOXIDES PRODUCED IN THE OXIDATION OF N-ACETYLATED DIHYDROPYRAZINES AND TETRAHYDROPYRAZINES BY SINGLET OXYGEN, DIMETHYLDIOXIRANE, AND M-CHLOROPEROXYBENZOIC ACID

The oxidation of the N-acylated pyrazine derivatives 1a,b gave the pyrazine-type dioxetanes 2a,b, which for the first time were isolated and characterized. The halflives of the thermal decomposition of these labile dioxetanes at 20 degrees C were determined by chemiluminescence measurements to be 80 +/- 2 (2a) and 18 +/- 1 min (2b). Upon thermolysis, the dioxetanes 2a,b decomposed quantitatively to the corresponding C-2-C-3 cleavage products 3a,b. The deoxygenation of the dioxetanes 2a,b by dimethyl sulfide yielded predominantly the novel pyrazine-type epoxides 4a,b, accompanied by some dioxetane decomposition product 3a,b. Upon thermolysis, the epoxide 4b decomposed to the benzodiazine 5b and the enone 6b. Dimethyldioxirane oxidation of the pyrazine derivatives 1a,b afforded the epoxides 4a,b, while treatment with an excess of m-chloroperoxybenzoic acid (m-CPBA) led to the C-2-C-3 cleavage products 3a,b with intense light emission by way of the intermediary peroxy esters 8.