Isodiazotates

When an aqueous solution of benzenediazonium chloride is added to a cold concentrated solution of potassium hydroxide, the unstable potassium diazo-tate, C(HjN NOK, is formed, and this when heated with alkali to 130° changes to the isomeric but far more stable potassium isodiazotate it is probable that these copipounds have the structures (A) and (B) respectively. 

Hantzsoh and Lehmann, Ber., 1902, 35, 897. According to Thiele (Annalen, 1910, 376, 253) methyl isodiazotate (probably a stereoisomeride) also yields diazomethane. 

Since o- and p-nitrodiazo compounds are rearranged, even by soda, to the noncoupling isodiazotates, it is desirable to work with these in the absence of soda and to use, instead, sodium acetate, or, in special cases, an acid-binding agent such as calcium carbonate or magnesia, so that the solution is never alkaline. 

The isodiazotate salts (19) of 2-amino-3-methyl- and 3-amino-2,5-dimethyl-pyrazines (17, R =R = H R = Me R = R = Me, R = H, respectively) [prepared from the corresponding amine by refluxing with sodium amide in diethyl ether and allowing the resulting sodium salt (18) to react with isoamyl nitrite] on treatment with hydriodic acid gave 2-amino-5-iodo-3-methyl- and 2-amino-5-iodo-... 

Hydroxy-, 2-hydroxy-3-methyl-, 2diydroxy-3,6-dimethyl-(3diydroxy-2,5-di-methyl-), and 2-hydroxy-3-ethylpyrazines have been prepared by hydrolysis of the corresponding isodiazotate salts (3) in cold 40% aqueous sulfuric acid in 42-72%... 

The diazotization of aminopyrazines has been described in earlier sections. Section V.IH records the preparation of 2-fluoropyrazine from 2-aminopyrazine in fluoroboric acid containing copper powder with sodium nitrite (882, 884) and Section V.ll the preparation of iodopyrazines from some aminopyrazines via isodiazotate salts (30) (887). These salts were assigned the isodiazotate structure, on the basis of their inability to couple with 0-naphthol in alkaline solution (887) and they were characterized by hydrolysis in cold 40% aqueous sulfuric acid to the hydroxypyrazine (887). Section V.I K describes the conversion of aminopyrazines to bromopyrazines (798, 800, 807, 890-892) for example, 2-amino-3-methoxy-carbonylpyrazine with hydrobromic acid, bromine, and sodium nitrite in water gave 2-bromo-3-methoxycarbonylpyrazine (798, 890). The diazotization of aminopyrazines to hydroxypyrazines has been described in Section VI. 1C, to alkoxy-pyrazines in Section V1.3C, and to oxopyrazines in Section V1.9A(5). 2-Amino-pyrazine with isopentyl nitrite in benzene gave 2-phenylpyrazine (45%) and some 2-isopentoxypyrazine and 2,2 -dipyrazinyl amino isomers (1211). 

---