1-(Phenylthio)- and 1-(hydroxycarbonylmethylthio)-4-methylphthalazines were prepared from 1-chloro-4-methylphthalazines (1). A series of 2-benzyl- and benzenesulphonyl derivatives was prepared from the corresponding halides and 4-methyl-1(2H)-phthalazinone (4). 4-Methyl-1(2H)-phthalazinthione (6) was substituted at SH group to give 1-(benzylthio)- and 1-(ethoxycarbonylmethylthio)-4-methylphthalazines, 7 and 8 respectively. Treatment of hydrazine hydrate with 8 produced 1-hydrazino-4-methylphthalazine (10). However, when the latter compound was treated with 1 it gave 1,2-bis-(4-methylphthalazinyl)hydrazine.
Treatment of 10 with aromatic aldehydes in glacial acetic acid gave the corresponding 3-phenyl-s-triazolo-[3,4-a]-6-methylphthalazines 13. 1-Hydrazino-4-methylphthalazine (10) underwent cyclization reactions with acetic anhydride, ethyl chloroformate, carbon disulphide, ethylformate, ethyl oxalate and with nitrous acid to give the corresponding triazolo-, triazino- and tetrazolophthalazine compounds