Molecular iodine mediated transition-metal-free oxidative dehydrogenation of 4,7-dihydropyrazolo[3,4-b]pyridines

A transition-metal-free Iodine-K2CO3 catalyzed efficient oxidation of 4,7-dihydropyrazolo[3,4-b]pyridines has been developed for the practical synthesis of corresponding pyrazolo[3,4-b]pyridines. The method is suitable for synthesis of variously substituted pyrazolo[3,4-b]pyridines as it is free from tedious purification steps and gives pure products in high yields. Molecular iodine (I-2), being inexpensive, environmentally benign, and easy-to-handle reagent, was used to carry out the dehydrogenation under mild reaction conditions.