A new heterocyclization in the series of acetylenic derivatives of anthraquinone

Article abstract of DOI:10.1007/BF01431813

2-Alkynyl-1-amino-9,10-anthraquinones react with HNO₂ in a mixture of dilute HCl and dioxane at 20°C to give 1,1-dichloroalkyl-1H-3-naphtho[2,3-g]indazole-6,11-diones. This reaction differs from the known cyclization of ortho-alkynylbenzenediazonium salts involving the formation of a pyridazine ring (the Richter synthesis of 4-hydroxy- and 4-halocinnolines).