Progress in the Synthesis of Oxindole‐Naphthoquinone Molecular Hybrid Scaffolds: A Concise Review

Oxindole and 1,4‐Naphthoquinone both are the versatile heterocyclic scaffolds which not only found in many naturally occurring and pharmaceutically imperative compounds but also have explored as an important precursor in the synthesis of a library of structurally diverse molecular frameworks desirable for biological studies. For a few decades, significant emphasis is given on the synthesis of both of these important privileged scaffolds to accomplish promising new heterocycles with chemical and biomedical relevance. Due to such prevalence and prominence of oxindole and 1,4‐naphthoquinone frameworks in medicinal and synthetic chemistry, many researchers have taken efforts to synthesize the oxindole‐naphthoquinone molecular hybrid in a single nucleolus. These efforts have led to the development of different approaches and green technologies in recent years, which includes nano catalysts, microwaves and, ultrasound irradiation. In this review, we have focused our attention, specifically, to provide insight into the modern approaches to the synthesis of oxindole‐1,4‐naphthoquinone molecular hybrid and technical advances in this research field till April 2020. The review is mainly made up of four main parts which contain 2‐component, 3‐component, 4‐component, and other multistep miscellaneous approaches utilized to synthesize this oxindole‐1,4‐naphthoquinone molecular hybrid. These four main parts are also subdivided according to different substituents present on oxindole‐1,4‐naphthoquinone molecular hybrid. This review focused specifically on the collection of literature on the reaction of isatin with 2‐hydroxyl‐1,4‐naphthoquinone(Lawsone) to afford oxindole‐1,4‐naphthoquinone molecular hybrid.