Process for preparation of pyrazolo[4,3-d]pyrimidin-7-ones and intermediates thereof

Abstract

A process is provided for the preparation of a compound of formulae (IA) (sidenafil) and (IB) comprising reacting a compound of formula (IIA) and (IIB) respectively in the presence of − OR, wherein R in the case of formation of compound (IA) is CH 2 CH 3 and R in the case of formation of compound (IB) is CH 2 CH 2 CH 3 , where X is a leaving group:

1 . A process for the preparation of a compound of formula (IA) or (IB) below:  
                   
       comprising reacting a compound of formula (IIA) or (IIB) respectively  
                 
 
       in the presence of  − OR, wherein R in the case of formation of compound (IA) is CH 2 CH 3  and R in the case of formation of compound (IB) is CH 2 CH 2 CH 3 , and wherein X is a leaving group.  
     
     
         2 . A process as claimed in    claim 1    wherein X is selected from the group consisting of arylsulphonyloxy, C 1 -C 4  alkylsulphonyloxy, nitro or halo substituted benzenesulphonyloxy, C 1 -C 4  perfluoroalkylsulphonyloxy, aroyloxy, substituted aroyloxy, C 1 -C 4  perfluoroalkanoyloxy, C 1 -C 4  alkanoyloxy, halo; diazonium; C 1 -C 4  primary and secondary alkoxy, oxonium, perchloryloxy, quatenaryammonium C 1 -C 4  alkylsulphonuloxy, halosulphonyloxy, halonium and diarylsulphonylamino.  
     
     
         3 . A process as claimed in    claim 2    wherein X is a halo or methoxy.  
     
     
         4 . A process as claimed in    claim 3    wherein X is fluoro, chloro or methoxy.  
     
     
         5 . A process as claimed in    claim 4    wherein X is fluoro or chloro.  
     
     
         6 . A process as claimed in    claim 1    wherein  − OR is present with an auxiliary base.  
     
     
         7 . A process as claimed in    claim 6    wherein the auxiliary base is selected from the group consisting of sterically hindered base, a metal salt of 1-methyl piperazine, 1-ethylpiperazine, morpholine, a metal hydride, metal oxide, metal carbonate and metal bicarbonate.  
     
     
         8 . A process as claimed in    claim 7    wherein the sterically hindered base is a metal salt of a sterically hindered alcohol or amine.  
     
     
         9 . A process as claimed in    claim 8    wherein the metal salt of a sterically hindered alcohol or amine is selected from the group consisting of a secondary or tertiary C 4 -C 12  alkanol, a C 3 -C 12  cycloalkanol and a secondary or tertiary (C 3 -C 8  cycloalkyl)C 1 -C 6  alkanol, a N-(secondary or tertiary C 3 -C 6  alkyl)-N-(primary, secondary or tertiary C 3 -C 6  alkyl)amine, a N-(C 3 -C 8  cycloalkyl)-N-(primary, secondary or tertiary C 3 -C 6  alkyl)amine, a di(C 3 -C 8  cycloalkyl)amine or hexamethyldisilazane 1,5-diazabicyclo[4,3,0]non-5-ene 1,8-diazabicyclo[5,4,0]undec-7-ene and a tertiary amine.  
     
     
         10 . A process as claimed in    claim 9    wherein the auxiliary base is a metal salt of a tertiary alkanol.  
     
     
         11 . A process as claimed in    claim 1    wherein the reaction is carried out in an inert solvent or ROH or a mixture of an inert solvent and ROH.  
     
     
         12 . A process as claimed in    claim 11    wherein the solvent is selected from the group consisting of ethanol, n-propanol, a secondary or tertiary C 4 -C 12  alkanol, a C 3 -C 12  cycloalkanol, a tertiary C 4 -C 12  cycloalkanol, a secondary or tertiary (C 3 -C 7  cycloalkyl)C 2 -C 6  alkanol, a C 3 -C 9  alkanone, 1,2-dimethoxyethane, 1,2-diethoxyethane, diglyme, tetrahydrofuran, 1,4-dioxan, toluene, xylene, chlorobenzene, 1,2-dichlorobenzene, acetonitrile, dimethyl sulphoxide, sulpholane, dimethylformamide, N-methylpyrrolidin-2-one, pyridine, and mixtures thereof.  
     
     
         13 . A process as claimed in    claim 12    wherein the solvent is selected from the group consisting of ethanol, n-propanol, a tertiary C 4 -C 12  alkanol, a tertiary C 4 -C 12  cycloalkanol, a tertiary (C 3 -C 7  cycloalkyl)C 2 -C 6  alkanol, a C 3 -C 9  alkanone, 1,2-dimethoxyethane, 1,2-diethoxyethane, diglyme, tetrahydrofuran, 1,4-dioxan, toluene, xylene, chlorobenzene, 1,2-dichlorobenzene, acetonitrile, sulpholane, dimethylformamide, N-methylpyrrolidin-2-one, pyridine, and mixtures thereof.  
     
     
         14 . A process as claimed in    claim 13    wherein the solvent is ethanol or propanol.  
     
     
         15 . A process for the preparation of a compound of formula (IA) or (IB) below:  
                   
       comprising reacting a compound of formula (IIA) or (IIB) respectively  
                 
 
       in the presence of  − OR, wherein R in the case of formation of compound (IA) is CH 2 CH 3  and R in the case of formation of compound (IB) is CH 2 CH 2 CH 3 , or  − OR together with an auxiliary base or ZOR together with an auxiliary base wherein ZOR is a salt of  − OR and Z is cation.  
     
     
         16 . A process as claimed in    claim 15    for the production of compound (IA)  
                 
 
       comprising reacting compound (IIA):  
                 

 a) with ethanol and auxiliary base, optionally in an inert solvent; or  
 b) with ZOEt and an auxiliary base in ethanol or an inert solvent or a mixture thereof; or  
 c) with ZOEt and ethanol or an inert solvent or a mixture thereof wherein Z is a cation.  
 
     
     
         17 . A process as claimed in    claim 15    for the production of compound (IB)  
                 
 
       comprising reacting compound (IIB):  
                 

 a) with propanol and an auxiliary base, optionally in an inert solvent; or  
 b) with ZOPr and an auxiliary base, in propanol or an inert solvent or a mixture of both; or  
 c) with ZOPr, and propanol or an inert solvent or a mixture of both wherein Z is a cation.  
 
     
     
         18 . A process as claimed in    claim 16    wherein the compound of formula (IIA) is prepared by coupling a compound of formula (VIIA)  
                 
 
       with a compound of formula (IXA)  
                 
 
     
     
         19 . A process as claimed in    claim 17    wherein a compound of formula (IB) is prepared by coupling a compound of formula (VIIB)  
                 
 
       with a compound of formula (IXB)  
                 
 
     
     
         20 . A process as claimed in    claim 18    wherein a compound of the formula (VIIA) is formed by coupling a compound of formula (VIA) with N-methylpiperazine  
                 
 
     
     
         21 . A process as claimed in    claim 19    wherein a compound of formula (VIIB) is formed by coupling a compound of formula (VIA) with N-ethylpiperazine.  
                 
 
     
     
         22 . A compound of formula (IIA) or (IIB):  
                   
       wherein X is a leaving group.  
     
     
         23 . A compound of formula (IIIA) or (IIIB):  
                   
       wherein X is a leaving group.  
     
     
         24 . A compound of formula (VIIA) or (VIIB)  
                   
       wherein X is a leaving group.  
     
     
         25 . A compound according to    claim 22    wherein X is selected from the group consisting of fluoro, chloro and methoxy.  
     
     
         26 . A compound according to    claim 23    wherein X is selected from the group consisting of fluoro, chloro and methoxy.  
     
     
         27 . A compound according to    claim 24    wherein X is selected from the group consisting of fluoro, chloro and methoxy.