Butanoic acid, 2-ethyl-3-oxo-, ethyl ester → 6-ethyl-3,7-dimethyl-5-oxo-5H-thiazolo[3,2-a]pyrimidine-2-carboxylic acid, ethyl ester
Reaction equation
[NH2:1][C:2]1[S:3][C:4]([C:8]([O:10][CH2:11][CH3:12])=[O:9])=[C:5]([CH3:7])[N:6]=1.[CH2:13]([CH:15]([C:21]([CH3:23])=O)[C:16](OCC)=[O:17])[CH3:14]>>[CH2:21]([C:15]1[C:16](=[O:17])[N:6]2[C:5]([CH3:7])=[C:4]([C:8]([O:10][CH2:11][CH3:12])=[O:9])[S:3][C:2]2=[N:1][C:13]=1[CH3:14])[CH3:23]Participants
3
Conditions
- Temperature
- 100 °C
Procedure
2-amino-4-methyl-thiazole-5-carboxylic acid, ethyl ester (10 g) was reacted with ethyl 2-ethyl-acetoacetate (17 g) in polyphosphoric acid (50 g) under stirring at 100° C. for 4 hours. After cooling, dilution with ice water and neutralization with 35% NaOH, the precipitate was filtered, washed with water until neutral and crystallized from hexane to give 6-ethyl-3,7-dimethyl-5-oxo-5H-thiazolo[3,2-a]pyrimidine-2-carboxylic acid, ethyl ester, m.p. 122°-124° C. (9.9 g) which was reacted with N-bromo succinimide (13.75 g) in benzene (260 ml) at the reflux temperature for 11 hours.