SYNTHESIS OF CONDENSED TRICYCLIC PYRAZOLO[3,4-B]THIENO[2,3-D]PYRIDINEAND RELATED ISOSTERE DERIVATIVES [A]

In this paper we report the synthesis of an isosteric series of new he terotricyclic derivatives, corresponding to pyrazolo[3,4-b]thieno[2,3- d]pyridine (1), pyrazolo[3,4-b] furano[2,3-d]pyridine (2) and pyrazolo [3,4-b]pyrrolo[2,3-d]pyridine (3). These functionalized compounds were obtained, in high overall yield, by an 'one-pot' reaction of the chlo roester intermediate 4, possessing the pyrazolo[3,4-b]pyridine system, with an adequate alpha-hetero-acetyl ester derivative, in SNAr/Dieckm an cyclization type consecutive reactions.