FeCl₃‑Catalyzed Combinatorial Synthesis of Functionalized Spiro[Indolo-3,10′-indeno [1,2‑<i>b</i>]quinolin]-trione Derivatives

An efficient, inexpensive, environmentally friendly and high yield one-pot route to new spiro­[indolo-3,10′-indeno [1,2-b]­quinolin]-trione derivatives has been developed, involving three-component reaction of enaminones, N-substituted isatins and Indane-1,3-dione catalyzed by FeCl3. The approach to this spiro-heterocycle is noteworthy because it results in the formation of three new σ (two C–C and one C–N) bonds in a single operation, leading to the construction of novel spiro skeleton. This method works on a large scale in excellent yields.