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 spiroindoline-3,3'-pyridine-2,2'-diones in excellent yields.
Wei et al. (Fri,) studied this question.