Diastereo‐ and Enantioselective Synthesis of Spiro‐Pyrrolidine‐Pyrazolones by Squaramide‐Catalyzed Cascade Aza‐Michael/Michael Reactions

Abstract

Abstract A new method was developed to rapidly generate a series of spiro‐pyrrolidine‐pyrazolones by using a squaramide‐catalyzed cascade aza‐Michael/Michael addition of either tosylaminomethyl enones or enoates to unsaturated pyrazolones. This tandem reaction sequence proceeded well by using 5 mol‐% of a chiral bifunctional tertiary amine squaramide catalyst to afford the desired products in good to excellent yields (up to 98 %) with excellent diastereoselectivities [up to >20:1 diastereomeric ratio ( dr )] and high to excellent enantioselectivities (up to 98 % ee ).