Synthesis and Substitution of 1,3,4,6-Tetra-substituted-3,6-dihalogeno-2,5-piperazinediones

Addition of chlorine to 3,6-dimethylene- (3) and 3,6-dibenzylidene-1,4-dimethyl-2,5-piperazinediones gave isomers of the corresponding tetrachloride, and substitution of 1,3,4,6-tetramethyl-2,5-piperazinedione with bromine also gave tetrabromide (2) of the same type via successive elimination and addition reactions. Treatment of 2 with water and with methanolic sodium acetate gave the corresponding 3,6-dihydroxy and dimethoxy derivatives, respectively, while treatment with sodium iodide, sodium sulfide, sodium thiocyanate, or sodium thioacetate gave only 3 and sulfur in a good yield. Similar results were obtained in the case of octahydro-5H,10H-dipyrrolo[1,2-a: 1′,2′-d]pyrazine-5,10-dione. However, bromination of 6,13-dioxo-6a,7,13a,14-tetrahydro-6H,13H-pyrazino[1,2-a: 4,5-a′]diindole gave rise only to aromatization. Configurations of the isomers obtained and the reaction processes were discussed.