Catalyst-Free One-Pot Tandem Reduction of Oxo and Ene/Yne Functionalities by Hydrazine: Synthesis of Substituted Oxindoles from Isatins.

An unprecedented one-pot tandem reduction of oxo and ene/yne functionalities of substituted isatins is disclosed for the synthesis of oxindole derivatives in excellent yields. The reaction is simply performed by treating N-(2-alkenyl)/propargylisatins with an excess amount of hydrazine hydrate (25%) under catalyst-free refluxing conditions. The reduction process appears to be quite unique and proceeds quite efficiently without the aid of any catalyst at ambient pressure. [ABSTRACT FROM AUTHOR]