[CH3:1][C:2]1([CH3:18])[CH2:15][C:6]2[N:7]=[C:8]([NH:10][C:11]([NH:13][CH3:14])=[O:12])[S:9][C:5]=2[C:4]([CH3:17])([CH3:16])[CH2:3]1.[CH2:19]1[O:24][CH2:23]OCO1.S(=O)(=O)(O)O.[OH-].[Na+]>O>[CH3:1][C:2]1([CH3:18])[CH2:15][C:6]2[N:7]=[C:8]([N:10]3[C:11](=[O:12])[N:13]([CH3:14])[CH2:23][O:24][CH2:19]3)[S:9][C:5]=2[C:4]([CH3:17])([CH3:16])[CH2:3]1Sulfuric acid, 85% concentration (40 grams) was charged into a glass reaction vessel fitted with a mechanical stirrer and a thermometer and was cooled to about 5° C. N-(5,5,7,7-tetramethyl-4,5,6,7-tetrahydrobenzothiazol-2-yl)-N'-methylurea (4.1 grams; 0.015 mole) and s-trioxane (1.4 grams, 0.015 mole) were added portionwise, with stirring, to the cold sulfuric acid. Stirring was continued for a period of about 16 hours at a temperature of about 20°-25° C. The reaction mixture was then diluted 1:1 with water and neutralized with aqueous 40% sodium hydroxide. The neutralized mixture was filtered and the solid obtained was washed with 3-100 ml portions of water and air dried to yield the desired product 3-(5,5,7,7-tetramethyl-4,5,6,7-tetrahydro-benzothiazol-2-yl)-5methyltetrahydro-1,3,5-oxadiazin-4-one as a solid having a melting point of 138°-140° C. Elemental analysis: Theory: C: 58.22%; H: 7.49%; N: 13.58%; Found: C:57.53%; H: 7.57%; N: 13.61 %.
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