Constructing spirooxindoles from non-oxindole precursors: a one-pot nitro-reduction/double lactamization approach to spiro[indoline-3,3′-quinoline]-2,2′-diones†

2-(2-Nitrobenzyl)-2-(2-nitrophenyl)malonates, readily prepared by S_NAr-arylation of diethyl malonate with o-fluoronitrobenzenes, followed by S_N2-alkylatioin of the resulting products with o-nitrobenzyl bromides, undergo a tandem Fe/AcOH-promoted nitro-reduction and double lactamization sequence to afford spiro[indoline-3,3′-quinoline]-2,2′-diones in high overall yields. The method is operationally simple, economical, and has a broad substrate scope. The synthetic practicality of this methodology was illustrated by performing the reaction on a gram scale with the same efficiency.