1977 年 97 巻 9 号 p. 962-967
In order to improve the facile cleavage of the C2-N bond on N-acetylation of 1, 3-diazines, various conditions for N-acetylation were examined with three kinds of 1, 3-diazines. Three acetylating reagents (acetyl chloride, acetic anhydride, and ethyl acetate) were used. Results were as follows : (1) For the synthesis of 1-acetyl-2-methyl-1, 4, 5, 6-tetrahydropyrimidine, 1, 3-diacetyl-2-methylhexahydropyrimidine, and 1-acetyl-3-methylhexahydropyrimidine, it is most suitable to react the starting compound with acetyl chloride in absolute benzene. (2) Water is required for the synthesis of 1-acetyl-2-hydroxy-2-methylhexahydropyrimidine. (3) Acetic anhydride is the most suitable reagent for synthesis of 1, 3-diacetyl-2-exomethylenehexahydropyrimidine. On N-acetylation of 2-methyl-1, 4, 5, 6-tetrahydropyrimidine, C2-N1 bond of the intermediate is split to N, N'-diacetyltrimethylenediamine, and the mechanism of such a cleavage is discussed.