MESOIONIC DIMETHYL DERIVATIVES OF SOME 1,2,4-TRIAZINONES - THE COURSEOF THE REACTION OF 3,5-DIMETHOXY, 3-METHOXY-5-METHYLTHIO, 5-METHOXY-3-METHYLTHIO AND 3,5-BIS(METHYLTHIO)-1,2,4-TRIAZINE WITH METHYL-IODIDE

Treatment of 3,5-dimethoxy-1,2,4-triazine (1a) with methyl iodide was found to give depending on the reaction time triazinium iodide 2a, tri aziniumolates 4a and 6a as well as methoxytriazinones 7a and 8a. Therm olysis of 2a gave triaziniumolates 4a and 6a. Reaction of 2a, 4a or me thoxytriazinone 9a with methyl iodide in acetonitrile yielded as the s ole product 6a. Reaction of 3-methoxy-5-methylthio-1,2,4-triazine (1b) with methyl iodide gave triazinium iodide 2b and methylthio triazinon e 7b. Hydrolysis of 2a,b afforded 4a. Reaction of 5-methoxy-3-methylth io-1,2,4-triazine (1c) with methyl iodide gave triazinium iodide 2c, t riaziniumolate 4b, triazinium iodide 5b and triazinone 8b. Hydrolysis of 2c yielded 4b and its thermolysis gave a mixture of 4b and 5b. Reac tion of 2c, 4b and triazinone 9b with methyl iodide afforded 5b. Treat ment of 3,5-bis(methylthio)-1,2,4-triazine (1d) with methyl iodide was found to give a mixture of N1 and N2 methiodides 2d and 3d which gave on hydrolysis 4b and 8b, respectively. Methylation of 6-methyl deriva tives 1e-g gave analogous results, however the proportions of N1 methy lated products were lower and the reaction rates higher in comparison to their respective lower homologues 1a,c,d. The structures of the mes oionic dimethyl derivatives were assigned from uv, ir, H-1 nmr and ele ctron impact mass spectra. The structural assignments were eventually confirmed by quantum chemical calculations of net charge distributions , bond lengths and ipso angles of the C5-O bonds.