Synthetic Studies Connected with the Preparation of 4-Cyclopropyl-7-fluoro-6-(4-methylpiperazin-1-yl)-1,2,4,9-tetrahydrothiazolo[5,4-b]quinoline-2,9-dione

Abstract

Target 4-cyclopropyl-7-fluoro-6-(4-methylpiperazin-1-yl)-1,2,4,9-tetrahydrothiazolo[5,4-b]quinoline-2,9-dione (5a) was obtained from 3-amino-1-cyclopropyl-6-fluoro-7-(4-methylpiperazin-1-yl)-2-mercaptoquinolin-4(1H)-one (9b). This intermediate was obtained from 3-amino-1-cyclopropyl- 6,7-difluoro-2-(methylsulfinyl)quinolin-4(1H)-one (9f) via 3-amino-1-cyclopropyl-6-fluoro-7-(4-methylpiperazin-1-yl)-2-(methylsulfinyl)quinolin-4(1H)-one (9c). Compound 9f was prepared from 2,4,5-trifluoroacetophenone (6a) in several steps. 4-Cyclopropyl-6,7-difluoro-2,3,4,9-tetrahydrothiazolo[5,4-b]quinoline-3,4-dione (5b) was prepared similarly as the target compound. Treatment of 5b with N-methylpiperazine did not afford 5a but 1-cyclopropyl-6,7-difluoro-2-mercapto-3-[(4-methylpiperazin-1-yl)carbonylamino]quinolin-4(1H)-one (11). Several unsuccessful attempts to prepare compound 5a and/or some useful intermediates of its synthesis are also described.