DABCO Promoted Regioselective Synthesis of New Diversely Functionalized 3-Hydroxy-2-Oxindole Scaffolds

An efficient and highly regioselective gamma-addition of beta-keto sulfones on isatins has been achieved in the presence of a catalytic amount of 1,4-diazabicyclo[2.2.2]octane (DABCO) to afford a gamma-(3-hydroxy-2-oxindole)-beta-keto sulfone structural framework. The scope of the method is tested by screening a series of isatin electrophiles as well as beta-keto sulfones. The described method was found to be very handy and provides straightforward access for the diversely functionalized 3-beta-keto sulfone substituted-3-hydroxy-2-oxindole structural scaffolds in very good yields from readily available starting materials under metal-free reaction conditions.