| abstract |
A process is provided for the preparation of a compound of formulae (IA) (sidenafil) and (IB) n n n 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: |