Process and intermediates for the preparation of oxophthalazinyl acetic acids and analogs thereof

Abstract From the Canadian patent

Oxophthalazinyl acetic acids having benzothiazole side chains are prepared by reacting an oxophthalazinyl thioacetamide acetate with hydrogen sulfide and a nitrophenyl compound having a reactive group such that the benzothiazole side chain may be formed by ring closure involving the thioacetamide group. The oxophthalazinyl thioacetamide may be prepared by reacting the corresponding cyanomethyloxophthalazinyl acetate with hydrogen sulfide in the presence of tertiary amines. Analogous indazole and oxopyridopyridazinone acetic acids may be prepared similarly as, well as oxophthalazinyl, indazole and oxopyridopyridazinone acetic acids having thiazolopyridinyl side chains.