Synthesis of Spiro[indoline-3,3′-pyridine]-2,2′-diones via an Annulo- and Diastereospecific [2 + 4] Annulation

A tandem
strategy has been designed and implemented for the efficient
synthesis of spirooxindoles from 3-diazoquinoline-2,4-diones with
α,β-unsaturated imines. The synthetic strategy involves
the ring-contractive Wolff rearrangement of 3-diazoquinoline-2,4-diones,
[2 + 4] annulation of α-oxoketenes with α,β-unsaturated
imines, and transannulation, affording annulo- and diastereospecific
spiro[indoline-3,3′-pyridine]-2,2′-diones in excellent
yields.