Asymmetric Synthesis of Trifluoromethyl Substituted Spiro[Indoline-3,4′-Pyrano[2,3-c]Pyrazole] Derivatives with Organocatalysts

Spirocyclic compounds have always attracted attention due to their presence as a structural core in a wide variety of natural and bioactive molecules and to exhibit pharmaceutical properties. An asymmetric synthesis of spiro[indoline-3,4 '-pyrano[2,3-c]pyrazoles] via Michael addition of trifluoromethyl substituted pyrazolone to isatylidene ethyl cyanoacetate derivatives was conducted with excellent enantioselectivities up to 99 % and up to 97 % isolated yield at room temperature with using 2 mol % of bifunctional quinine derived squaramide organocatalysts. Step into the intriguing world of enantiopure spirooxindoles: Bifunctional organocatalyst (see Picture) facilitates a highly enantioselective Michael addition of trifluoromethyl-substituted pyrazolone to isatylidene ethyl cyanoacetate derivatives at ambient temperature. image