CS[C:3]1[S:4][CH2:5][CH2:6][CH2:7][N:8]=1.[N+:9]([CH2:12][C:13]([O:15][CH2:16][CH3:17])=[O:14])([O-:11])=[O:10].CS>[Cl-].[Zn+2].[Cl-].CCOCC.C(O)(C)C>[N+:9]([C:12](=[C:3]1[NH:8][CH2:7][CH2:6][CH2:5][S:4]1)[C:13]([O:15][CH2:16][CH3:17])=[O:14])([O-:11])=[O:10]To a mixture of 235 g of 5,6-dihydro-2-(methylthio)-4H-1,3-thiazine (A. F. McKay et al., J. Am. Chem. Soc., 80, 3339 (1958)) and 2 g of zinc chloride at approximately 115° in a nitrogen atmosphere, 263 g of ethyl nitroacetate (S. Zen, et al., Kogyo Kagaku Zasshi, 74, 70 (1971)) was added dropwise over a 1.5 hour period. The mixture was held at 110°-120°. When evolution of methyl mercaptan ceased after 45 minutes further stirring of the heated mixture, 1 g of zinc chloride was added and the mixture was stirred at about 115° for 1.25 hours. An additional 1 g of zinc chloride then was added and stirring of the mixture at about 115° was continued for 1.5 hours. The mixture then was poured into a cooled solution of 2/1 (volume) ether/isopropyl alcohol mixture. The crystallized product was collected, washed with ether and dried under reduced pressure to leave a tan solid, m.p. 100° -102°, which on recrystallization from methanol gave ethyl nitro(tetrahydro-2H-1,3-thiazin-2-ylidene)acetate (1A) as a pale yellow solid, m.p. 105° -106°.
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