How to reduce 2-oxyindole ?

1. BH3. 0C.
slow reaction, low yielding, but can tolerate many functional groups, like ester.
can over reduced to indoline.

2. LAH
of course, amide can be reduced.

3. triflation first, then Pd/Et3SiH remove triflate.

4. lawesson's reagent to convert oxygen to sulfur, then reduce it by
Raney Ni.

5. some reducing reagent (red-al, super hydride...) under the help of acid (TFA, BF3-OEt2...)