Amino acids, isolation diazo derivatives

Oiazonium Salt Formation. The aromatic amino group of aminophenols can be converted to the diazonium salt using sodium nitrite in aqueous acid, although difficidties may be encoimtered when the aminophenol is of low solubiUty or easily oxidized Crystalline diazonium salts have been isolated using the hydrochloride or sidfate of the appropriate aminophenol under anhydrous conditions. Such diazo derivatives find extensive use in the dye industry (27,28). 

Following their work on the synthesis of the parent compound 2,6-naphthyridine (105) (105). Taurins and Li reported their work in full (107) and at the same time reported a synthesis of the 4-methyl derivative 104, isolated by Harkiss and Swift (62). 4-Cyano-3-pyridyl-acetonitrile (275) was methylated (CFLI-NaOQHs) in the side chain to afford 2-(4-cyano-3-pyridyl)propionitrile (276), which was treated with hydrogen bromide in ether to afford 3-amino-l-bromo-4-methyl-2,6-naphthyridine (277). Diazo-tization/bromination and replacement of the bromine groups with hydrazine gave 278, and reaction with CuS04 in acetic acid afforded 4-methyl-2,6-naphthyridine (98) (Scheme 23) (107), whose spectroscopic properties were identical with those reported previously (62,63). 

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