[CH3:1][C:2]1[N:3]=[C:4]2[S:11][CH:10]=[CH:9][N:5]2[C:6](=[O:8])[CH:7]=1.C(OCC)(=O)CC(C)=O.[Br:21]N1C(=O)CCC1=O.C(Cl)(Cl)Cl>C1C=CC=CC=1>[Br:21][C:7]1[C:6](=[O:8])[N:5]2[CH:9]=[CH:10][S:11][C:4]2=[N:3][C:2]=1[CH3:1]7-methyl-5H-thiazolo[3,2-a]pyrimidine-5-one, m.p. 127°-129° C., (4 g), prepared according to Example 1 using ethyl acetoacetate, dissolved in benzene (100 ml) was reacted with N-bromo-succinimide (4.7 g) under stirring at room temperature for 1 hour. The precipitate was dissolved by adding chloroform and the solution was washed with water: evaporation in vacuo to dryness and crystallization of the residue from methanol gave 6-bromo-7-methyl-5H-thiazolo[3,2-a]pyrimidine-5-one, m.p. 233°-234° C. (5.1 g), which was reacted with 3-pyridine-carboxaldehyde (3.4 g) in methanol (190 ml) in the presence of sodium methoxide (2.2 g) under stirring at the reflux temperature for 2 hours. After cooling the precipitate was filtered and washed with water until neutral: crystallization from CH2Cl2 -methanol gave 5.18 g of 6-bromo-7-trans-[2-(3-pyridyl)-ethenyl]-5H-thiazolo[3,2-a]pyrimidine-5-one, m.p. 208°-209° C., NMR (CDCl3) δppm: 6.99 (d) (1H, C-2 proton), 7.33 (dd) (1H, C-5 pyridyl proton), 7.59 (d) (1H, β-ethenyl proton), 7.95 (d) (1H, α-ethenyl proton), 7.96 (d) (1H, C-3 proton), 7.98 (m) (1H, C-4 pyridyl proton), 8.58 (bd) (1H, C-6 pyridyl proton), 8.82 (bs) (1H, C-2 pyridyl proton); JHαHβ =16 Hz.
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