CS235196B1 - Method of 4,9-dihydro-3,9-dimethyl-4-oxo-1h-pyrazolo(3,4-b) quinoline - Google Patents

Abstract

The present invention relates to a new method of preparation 4,9-dihydro-3,9-dimethyl-4-oxo-1H-pyrazolo- (3,4-binoquinoline) heats 4,9-dihydro-2,3,9-trimethyl-4-oxo-2H- -pyrazolo [3,4-b] quinoline with hydrochloride pyridine to a temperature of 200 to 240 ° C, preferably at 220 ° C.

Description

The invention relates to a novel preparation process

4,9-Dihydro-3,9-dimethyl-4-oxo-1H-pyrazolo [3,4-b] quinoline of Formula I

Said compound of formula (I) serves as an intermediate for the preparation of biologically important substances, in particular having antiviral activity.

Said compound of formula (I) is a known substance, the preparation of which is characterized by heating 4- (2-fluorophenyl-6,3-dihydro-1,3,8-trimethylpyrazolo (3,4-e) (1, 2-fluorophenyl)). 4) diazepin-7 (1H) on with pyridine hydrochloride at 210-215 ° C [DeWald HA; J. Heterocyclic Chem. 11, 1061 (1974)].

Said compound of formula (I) was prepared by the process of the invention, characterized by heating 4,9-dihydro-2,3,9-trimethyl-4-oxo-2H-pyrazolo (3,4-b) quinoline (U.S. Pat. No. 235 168 with pyridine hydrochloride at a temperature of 200 to 240 ° C, preferably at a temperature of 220 ° C.

Given the ease of preparation of the starting 4,9-dlhydro-2,3,9-trimethyl-4-oxo-2H-pyrazolof 3,4-b) quinoline (cf. No. 235168), and the difficult preparation of 4- (2-fluorophenyl) 6,8-dihydro-1,3,8-trimethylpyrazolo [3,4-e] ((1,4) diazepin-7 (1H) -one), the advantageous preparation of the compound of formula I of the invention is evident.

The following exemplary embodiment illustrates the invention but does not limit it in any way.

Example

4,9-Dihydro-3,9-dimethyl-4-oxo-1H-pyrazolo [3,4-b] quinoline Water was distilled from a stirred mixture of 30 g of pyridine and 44 ml of concentrated hydrochloric acid by gradually increasing the temperature to 160 ° C. . At this temperature, 3.2 g of 4,9-dihydro-2,3,9-trimethyl-4-oxo-2H-pyrazolo [3,4-b] quinoline was added and the mixture was stirred at 220 ° C for 2 hours. After cooling to 160 ° C, the mixture was poured into 240 ml of water, the mixture was boiled and the insoluble matter was filtered off. The precipitate upon cooling of the filtrate was aspirated and washed with water. Crystals obtained by crystallization from ethanol were dried to constant weight at 110 ° C at 3 kPa. 2.32 g (77.7%) of m.p. 248.8-249.5 ° C were obtained.

Claims (1)

A process for the preparation of 4,9-dihydro-3,9-dimethyl-4-oxo-1H-pyrazolo [3,4-b] quinoline, characterized by heating 4,9-dihydro-2,3,9-trimethyl -4-oxo-2H-pyrazolo [3,4-b] quinoline with pyridine hydrochloride at a temperature of 200 to 240 ° C, preferably at a temperature of 220 ° C.