Pyrazino pyridazine-5,8-dione

Pyrazino[2,3-d]pyridazine-5,8-dione chlorination, 3, 347 lithiation, 3, 347 synthesis, 3, 359 Pyrazino[2,3- d]pyridazin-5-one reactivity, 3, 347 synthesis, 3, 360... 

Pyrazino[2,3-d]pyridazine-5,8-dione (420) can be prepared from pyrazine-2,3-dicarboxylic acid anhydride (419). Condensation of hydrazine with ethyl 5-acylpyridazine-4-carboxylates (421) gives pyridazino[4,5-d]pyridazin-l(2//)-ones (422) (79M365). 

Pyrazino[2,3-d]pyridazines undergo nucleophilic displacements readily. Pyrazino-[2,3-d]pyridazine-5,8-dione can be chlorinated in a mixture of phosphorus oxychloride and phosphorus pentachloride to give 5,8-dichloropyrazino[2,3-d]pyridazine. The corresponding dibromo product is prepared by reaction of the starting dione with phosphorus oxy-bromide and bromine. However, all attempts to chlorinate pyrazino[2,3-d]pyridazin-5-one failed (69JHC93). 

Pyrazino[2,3-d]pyridazine-5,8-dione (104) can be dithiated with phosphorus pentasulfide to give the unisolated intermediate (105), which yields the bis(benzylthio) product (106) on reaction with benzyl chloride. Acetylation and tosylation of this starting dione (104) produce the monoacetyl and the monotosyl products, respectively (66JHC512). 

Only one derivative of this ring system is reported in the literature, namely octahydro-1H-pyrazino[ 1,2-b ]pyridazine-5,8-dione (206) (71JCS(C)528). This compound is isolated in both the acid and base hydrolysis of the monamycins, a mixture of cyclohexadepsipeptide antibiotics. 

Pyrazino[2,3-rf]pyridazine-5,8-dione (2) can be prepared by oxidation with tert-butyl hypochlorite at — 77 °C in acetone from the corresponding dihydroxy compound 1. This compound, which is not stable and polymerizes on attempts to isolate it from solution, shows short-lived chemoluminescence with alkaline hydrogen peroxide.102... 

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