Synthesis of spiropyrazoline oxindoles by a formal [4 + 1] annulation reaction between 3-bromooxindoles and in situ-derived 1,2-diaza-1,3-dienes

Abstract

A formal [4 + 1] annulation reaction of 3-bromooxindoles and in situ-derived 1,2-diaza-1,3-dienes in the presence of Cs₂CO₃ as the base has been developed for the first time. This protocol provides an efficient and mild approach for the synthesis of various biologically interesting spiropyrazoline oxindoles in generally high yields. A one-pot, three-component variant also worked smoothly to give the desired products in comparable yields.