Synthesis of Spirooxindoles through Cyclocondensation of Isatin and Cyclic 1,3-Diones

Recent Progress in the Synthesis of Heterocycles Based on 1,3-Diketones

N,O-heterocycles containing the dicarbonyl ring play a significant role in heterocyclic and therapeutic chemistry. Since the discovery of 1,3-diketones, numerous research works have been achieved regarding the synthesis and its chemical reactivity. In this review, we have described the most relevant publications involving β-diketone compounds published during the period between 2018 to date. In addition, we include the 1,3-diketones-based heterocyclic compounds prepared by various synthetic methodologies.

Recent Strategies in the Synthesis of Spiroindole and Spirooxindole Scaffolds

Spiroindole and spirooxindole scaffolds are very important spiro-heterocyclic compounds in drug design processes. Significant attention has been directed at obtaining molecules based on spiroindole and spirooxindole derivatives that have bioactivity against cancer cells, microbes, and different types of disease affecting the human body. Due to their inherent three-dimensional nature and ability to project functionalities in all three dimensions, they have become biological targets. Considering reports on spiroindole and spirooxindole-containing scaffolds in the past decades, introducing novel synthetic procedures has been an active research field of organic chemistry for well over a century and will be useful in creating new therapeutic agents. This review summarizes the pharmacological significance of spiroindole and spirooxindole scaffolds and highlights the latest strategies for their synthesis, focusing particularly on the past 2 years with typical examples. The spiroindole and spirooxindoles in this review are divided by the type and ring size of the spirocycle that is fused to indole or oxindole. Summarizing these procedures will be very beneficial for discovering novel therapeutic candidate molecules.

Synthesis of new functionalized thiazolo pyridine-fused and thiazolo pyridopyrimidine-fused spirooxindoles via one-pot reactions

A sequential multi-component reaction of the nitroketene dithioacetals, cysteamine hydrochloride, isatin and different CH-acids is described. This efficient method provides new functionalized thiazolo pyridine-fused spirooxindoles and thiazolo pyridopyrimidine-fused spirooxindoles in good yields. In the case of using isatin derivatives (5-bromoisatin and 5-chloroisatin), the reaction was carried out by using nano-SiO2 (20 mol%) as an effective heterogeneous Lewis acid promoter. This type of reaction provides a range of skeletally different polycyclic spiro thiazole-based heterocyclic structures and represents attractive advantages including straightforward one-pot operation under the catalyst-free condition and simple workup procedures without using tedious purification procedure.