Switchable Chemoselectivity in [3 + 3] Annulation of β,γ-Unsaturated α-Ketoesters and 1 H- Pyrazol-5-amines by Cooperative Acid Catalysis with Ni II and In I .

The exchange of the metal ion from Ni(II) to In(I) leads to a switch in the chemoselectivity of the [3 + 3] annulation of β,γ-unsaturated α-ketoesters and 1 H- pyrazol-5-amines in the presence of phosphoric acid 1 , affording functionalized 1 H- pyrazolo[3,4- b ]pyridines 4 in up to 97% yields and highly enantioselective 4,5-dihydro-1 H -pyrazolo[3,4- b ]pyridines 5 in up to 92% yield and 99% ee.