Ethyl 6-fluoro-1-methyl-4-oxo-7-(1-piprazinyl)-4H-[1,3]thiazeto[3,2-a]quinoline-3-carboxylate

Uses

Ethyl 6-fluoro-1-methyl-4-oxo-7-(1-piprazinyl)-4H-[1,3]thiazeto[3,2-a]quinoline-3-carboxylate is an off-white to slightly yellow powder used as an intermediate for prulifloxacin.

Synthesis

The general procedure for the synthesis of ethyl 6-fluoro-7-piperazine-1-methyl-4-oxo-1,4-dihydro-[1,3]thiazepine[3,2-a]quinoline-3-carboxylate from ethyl 6,7-difluoro-1-methyl-4-oxo-1,4-dihydro-[1,3]thiazepine[3,2-a]quinoline-3-carboxylate and piperazine was carried out as follows: 50 g of ethyl 6,7-difluoro-1-methyl-4 -oxo-4H-[1,3]thiazino[3,2-a]quinoline-3-carboxylic acid ethyl ester was dissolved in 5 volumes of DMSO and heated to 60 °C. Subsequently, 40 g of piperazine was added and the reaction was kept stirred at 60°C for 4 hours. After completion of the reaction, the mixture was cooled to room temperature, 5 volumes of acetonitrile was added and stirring was continued at room temperature for 4 hours. The precipitate was collected by filtration and dried to give 52.8 g of ethyl 6-fluoro-7-piperazine-1-methyl-4-oxo-[1,3]thiazolocyclo[3,2-a]quinoline-3-carboxylate in 87% yield. After further purification, the yield of ethyl 6-fluoro-7-piperazine-1-methyl-4-oxo-[1,3]thiazolocyclo[3,2-a]quinoline-3-carboxylate was up to 99%.

References

[1] Patent: CN107383069, 2017, A. Location in patent: Paragraph 0061; 0062
[2] Patent: CN107501298, 2017, A. Location in patent: Paragraph 0055; 0056
[3] Journal of Medicinal Chemistry, 1992, vol. 35, # 25, p. 4727 - 4738
[4] Patent: US4843070, 1989, A
[5] Patent: WO2009/93268, 2009, A1. Location in patent: Page/Page column 15