Kinetic studies on the Hinsberg condensation were performed trying to improve yields and achieve regio‐selectivity in the attainment of benzene‐substituted 3‐methylquinoxalin‐2(1H)‐ones. The course of the reactions between o‐phenylenediamine (o‐PDA) and substituted o‐PDA with pyruvic acid (2a) or ethyl pyruvate (2b) were followed by uv spectrophotometry at different pH values. The formation of 3‐methylquinoxalin‐2(1H)‐one (6a) was improved using sulphuric acid‐water mixtures, in which the reaction proceeded by a different mechanism. 3‐Methyl‐7‐methoxyquinoxalin‐2(1H)‐one (7b) was regioselectively synthesized independently of the pH of the reaction media. Reaction of 2‐amino‐4‐methylamine (1c) with 2a or 2b led to a mixture of 6 and 7‐quinoxalinone isomers, 6c and 7c, while 2‐amino‐4‐nitroaniline (1d) and 2,4‐diaminoaniline (1e) with 2a or 2b did not afford the heterocycle. In every case reactions with 2a were 100–1000 times faster than those with 2b. Mechanisms are proposed trying to account for the experimental results.

The synthesis of pyridinium‐quinolone chlorides and ylides, a pyridinium‐methylquinazolone ylide, 9‐pyridinium acridine chloride, and their behaviour by treatment with boiling aniline are described.

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The condensation of phthalic anhydride with 1,3-propanediamine afforded N-(0-carboxybenzoyl)-l,3-propanediamine (I) which by intravolecular cyclization was trarisformed into 2,3,4,6-btetrahydropyrimido[2,la]isoindol-6-one (11) rather than the benzodiazonine (111). An intermediate in the condensation is proposed. The reaction of 1,3-propanediamine with dimethyl phthalate also did not afford 111, but rather a more complex product, dibenzo[c,Z]-1,6,10,15tetraazacyclooctadecane-5,11,16,22-tetraone (IX).Reaction of 1,3-~ropanediamine with phthaloyl chloride gave 6,13-propanodibenz[c,h 3-1,6-diazecine-5,7,12,14-tetrone (XII). Spectro-scoDic data of the heterocycles obtained and chemical properties of I1 are given.