Iodide/H2O2 Catalyzed Intramolecular Oxidative Amination for the Synthesis of 3,2′-Pyrrolidinyl Spirooxindoles

Abstract

An ammonium iodide/hydrogen peroxide-mediated intramolecular oxidative amination of 3-aminoalkyl-2-oxindoles was achieved, affording the corresponding 3,2′-pyrrolidinyl spirooxindoles and their 6- or 7-membered analogous in moderate to high yields. This metal-free procedure features very mild reaction conditions, non-toxicity and easily handled hydrogen peroxide as a clean oxidant.

Optimizing the Iodide/Iodonium/O2 Oxidation Cycle Enhances the Scope, Selectivity, and Yields of Hydroiodic Acid‐Catalyzed Multicomponent Cyclocondensation Reactions

“…Other stoichiometric oxidants, including FeCl 3 and nitrobenzene [51,52] also raise the yield, but iodide salts are both inexpensive and environmentally benign relative to other oxidants. Oxygen is by far the most attractive terminal oxidant, strongly favoring optimization of the I − /O 2 /H 2 O 2 cycle for further synthetic development and large‐scale applications [45,53,54] …”

Transition metal-catalyzed synthesis of spirooxindoles

“…Expeditious development occurred in the eld of spirooxindole synthesis from 2012 to 2020. [18][19][20] The synthesis of spirooxindoles catalyzed by different reagents has been reported which includes iodine/H 2 O 2 , 21 amine, 22 bcyclodextrin, 23 L-proline, 24 ethylenediaminediacetate, 25 imidazole, 26 citric acid 27 and many others. Transition metals are efficient catalysts, as they are facile in losing and gaining of electrons, and most of them are malleable, ductile and easily available.…”