Compounds of the formula ##STR1## wherein R.sup.1 is H, C.sub.1 -C.sub.3 alkyl, C.sub.3 -C.sub.5 cycloalkyl or C.sub.1 -C.sub.3 perfluoroalkyl; R.sup.2 is H, C.sub.1 -C.sub.6 alkyl optionally substituted by OH, C.sub.1 -C.sub.3 alkoxy or C.sub.3 -C.sub.6 cycloalkyl, or C.sub.1 -C.sub.3 perfluoroalkyl; R.sup.3 is H, C.sub.1 -C.sub.6 alkyl, C.sub.3 -C.sub.6 alkenyl, C.sub.3 -C.sub.6 alkynyl, C.sub.3 -C.sub.7 cycloalkyl, C.sub.1 -C.sub.6 perfluoroalkyl or (C.sub.3 -C.sub.6 cycloalkyl)C.sub.1 -C.sub.6 alkyl; and Y is chloro, bromo, or fluoro. The above compounds are intermediates useful in the synthesis of certain pyrazolopyrimidinones which inhibit cyclic guanosine 3', 5'-monophosphate phosphodiesterase.
This is a division of application Ser. No. 08/084,827, U.S. Pat. No. 5,346,901 filed on Jun. 29, 1993, which is a division of application Ser. No. 07/882,988, now U.S. Pat. No. 5,250,534, filed on May 14, 1992, which is a Continuation of Ser. No. 07/717,227, filed on Jun. 18, 1991, abandoned.
Sildenafil, a known pharmaceutical chemical useful in treatment of male sexual dysfunction, is prepared by processes in which the final chemical intermediate is of significantly lower basicity than sildenafil itself, so that sildenafil can be extracted in substantially pure form from the organic reaction mixture in which it is made by adding an aqueous medium of appropriately chosen acidic pH and causing phase shift of the sildenafil to occur selectively into the aqueous phase.
1-Alkyl-pyrazole-5-carboxylic esters are obtained with surprisingly low proportions of 1-alkyl-pyrazole-3-carboxylic esters if a 2,4-diketo ester and/or an enolate thereof is reacted with an alkylhydrazine and/or a corresponding alkylhydrazinium salt, if appropriate, in the presence of a solvent and/or of water, in such a manner that during at least about 90% of the reaction free alkylhydrazine is present.
There is provided compounds of formula IA and of formula IB, ##STR1## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4 and A have meanings given in the description, which are useful in the curative and prophylactic treatment of a medical condition for which inhibition of a cyclic guanosine 3',5'-monophosphate phosphodiesterase (e.g. cGMP PDE5) is desired.
Compounds of the formulae (IA) and (IB): ##STR1## wherein R.sup.1 is C.sub.1 to C.sub.3 alkyl optionally substituted with phenyl, Het or a N-linked heterocyclic group selected from piperidinyl and morpholinyl; wherein said phenyl group is optionally substituted by one or more substitutents selected from C.sub.1 to C.sub.4 alkoxy; halo; CN; CF.sub.3 ; OCF.sub.3 or C.sub.1 to C.sub.4 alkyl wherein said C.sub.1 to C.sub.4 alkyl group is optionally substituted by C.sub.1 to C.sub.4 haloalkyl or haloalkoxy either of which is substituted by one or more halo atoms; R.sup.2 is C.sub.1 to C.sub.6 alkyl and R.sup.13 is OR.sup.3 or NR.sup.5 R.sup.6, or pharmaceutically or veterinarily acceptable salts thereof, or pharmaceutically or veterinarily acceptable solvates of either entity are potent and selective inhibitors of type 5 cyclic guanosine 3',5'-monophosphate phosphodiesterase (cGMP PDE5) and have utility in the treatment of, inter alia, male erectile dysfunction (MED) and female sexual dysfunction (FSD).
