A Facile Synthesis of Pyrido[2^′,3^′:3,4]pyrazolo[1,5-a]pyrimidine and Pyrido[2^′,3^′:3,4]pyrazolo[5,1-c][1,2,4]triazine Bearing a Thiophene Moiety

Scheme 1

Synthetic protocol to achieve the pivotal intermediate pyrazolo[3,4-b]pyridine derivative 11.