SCHEDULED MAINTENANCE
Stereoselective synthesis of spirooxindole derivatives using an organocatalyzed tandem Michael–Michael reaction†
Abstract
A highly efficient stereoselective method for the synthesis of functionalized spirooxindole derivatives with three stereogenic centers was realized through an organocatalytic tandem Michael–Michael reaction. By employing (S)-α,α-diphenylprolinol trimethylsilyl ether as the catalyst and N,N′-bis[3,5-bis(trifluoromethyl)phenyl]thiourea as the cocatalyst, the reaction between N-tritylisatylidenemalononitriles and (E)-7-alkyl-7-oxohept-5-enals yields the desired spirooxindole products in good yields (76–95%) and with excellent diastereoselectivities (up to 97 : 3 dr) and enantioselectivities (up to 98% ee), which can be stereoselectively converted into the spiro[indoline-3,8′-isoquinoline] derivative through an intramolecular reductive amination reaction.
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