Application of 3-methylene- and 3-(monosubstituted)alkylideneoxindoles in the Synthesis of Heterocyclic Compounds

3-(Monosubstituted)alkylideneoxindoles as one major part of the oxindoles are involved in many essential biologically active compounds, like as self-germination and tyrosine kinase inhibitors. They have been extensively used as starting materials for the synthesis of a large number of different heterocycles. The aim of this review is to give an overview of diverse methodologies that have been developed for the construction of 3-methylene and 3-(monosubstituted)alkylideneoxindoles and their utility in organic synthesis, highlighting the variety of compounds that can be directly accessed from single reactions over these systems and emphasizing the influence of the reaction conditions in the outcome of the transformations. The reactions are classified into three main categories: one-component, two-component, and multicomponent reactions.