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 pyr azine-type dioxetanes 2a,b, which for the first time were isolated and characterized. The halflives of the thermal decomposition of these la bile dioxetanes at 20 degrees C were determined by chemiluminescence m easurements to be 80 +/- 2 (2a) and 18 +/- 1 min (2b). Upon thermolysi s, 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 e poxides 4a,b, accompanied by some dioxetane decomposition product 3a,b . Upon thermolysis, the epoxide 4b decomposed to the benzodiazine 5b a nd the enone 6b. Dimethyldioxirane oxidation of the pyrazine derivativ es 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 produc ts 3a,b with intense light emission by way of the intermediary peroxy esters 8.