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 SAr-arylation of diethyl malonate with -fluoronitrobenzenes, followed by S2-alkylatioin of the resulting products with -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.