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.