Current Organic Synthesis - Volume 18, Issue 1, 2021

Background: Pyranoid spirofused sugar derivatives represent a class of compounds with a significant impact in the literature. From the structural point of view, the rigidity inferred by the spirofused entity has made these compounds object of interest mainly as enzymatic inhibitors, in particular, carbohydrate processing enzymes. Among them glycogen phosphorylase and sodium glucose co-transporter 2 are important target enzymes for diverse pathological states. Most of the developed compounds present the spirofused entity at the C1 position of the sugar moiety; nevertheless, spirofused entities can also be found at other sugar ring positions. The main spirofused entities encountered are spiroacetals/thioacetals, spiro-hydantoin and derivatives, spiro-isoxazolines, spiro-aminals, spiro-lactams, spiro-oxathiazole and spiro-oxazinanone, but also others are present. Objectives: The present review focuses on the most explored synthetic strategies for the preparation of this class of compounds, classified according to the position and structure of the spirofused moiety on the pyranoid scaffold. Moreover, the structures are correlated to their main biological activities or to their role as chiral auxiliaries. Conclusion: It is clear from the review that, among the different derivatives, the spirofused structures at position C1 of the pyranoid scaffold are the most represented and possess the most relevant enzymatic inhibitor activities. Nevertheless, great efforts have been devoted to the introduction of the spirofused entity also in the other positions, mainly for the preparation of biologically active compounds but also for the synthesis of chiral auxiliaries useful in asymmetric reactions; examples of such auxiliaries are the spirofused chiral 1,3-oxazolidin-2-ones and 1,3-oxazolidine-2-thiones.

The implementation of heterogeneous photo-nanocatalysts in organic syntheses has been investigated greatly in the last decade as a result of the increasing demand to achieve the organic reactions via the use of green approaches and through the availability of visible light source. Herein, the presented results describe the basic concepts and state-of-the-art of fundamental insight into key features that influence the catalytic performance in organic reactions to investigate and optimize a broad range of catalyzed organic transformations, that benefit the researchers in academia and chemical industry fields.

Background: Isatin (IST) is a crucial pharmacologically active compound, chemically known as indole- 1H-2,3-dione. Development of different IST based analogues acquired significant awareness because of its pronounced therapeutic importance such as analgesic, anticancer, anti-inflammatory, antitubercular, antimicrobial, antifungal, antiviral (effective against SARS coronavirus 3C protease) and many other activities, and represents an important class of heterocyclic compounds that can be used as a precursor for the synthesis of many useful drugs. Objective: Previously, many articles were reported on IST synthesis and its different pharmacological activities but herein, we mentioned 59 different synthesis schemes of several IST derivatives/hybrids derived from the substitution of the nitrogen, aromatic ring, the second and third position of IST along with most potent molecule among each of synthesized libraries with their structural activity relationship (SAR). Using these standardized approaches, several biologically important compounds were developed like sunitinib, nintedanib, indirubin, etc and several studies have been carried out nowadays to develop newer compounds having fewer side effects and also overcome the problem of resistance. Conclusion: This report critically reviews the different strategies for the designs and synthesis of several IST based compounds having different biological activities with SAR, which can favour further investigation and modification for the development of new and more potent entities.

Background: The reactivity of 4-(dicyanomethylene)-3-methyl-l-phenyl-2-pyrazoline-5-one DCNP 1 and its derivatives makes it valuable as a building block for the synthesis of heterocyclic compounds like pyrazolo- imidazoles, -thiazoles, spiropyridines, spiropyrroles, spiropyrans, and others. As a number of publications have reported on the reactivity of DCNP and its derivatives, we compiled some features of this interesting molecule. Objective: This article aims to review the preparation of DCNP, its reactivity, and application in heterocyclic and dyes synthesis. Conclusion: In this review, we have provided an overview of recent progress in the chemistry of DCNP and its significance in the synthesis of various classes of heterocyclic compounds and dyes. The unique reactivity of DCNP offers unprecedentedly mild reaction conditions for the generation of versatile cynomethylene dyes from a wide range of precursors, including amines, α-aminocarboxylic acids, their esters, phenols, malononitriles, and azacrown ethers. We anticipate that more innovative transformations involving DCNP will continue to emerge in the near future.

;Introduction: NiFe2O4@SiO2nPr@glucose catalyzed synthesis of novel 5-pyrazolin-1,2,4-triazazolidine- 3-ones (thiones). Materials and Methods: Amino glucose-functionalized silica-coated NiFe2O4 nanoparticles (NiFe2O4@SiO2 nPr@glucose amine or NiFe2O4@SiP@GA) were synthesized and characterized by X-ray powder diffraction (XRD), X-ray spectroscopy (EDX), transmission electron microscope (TEM), field emission scanning electron microscope (FE-SEM), vibrating sample magnetometry (VSM) and fourier transform infrared spectroscopy (FTIR). Results and Discussion: NiFe2O4@SiP@GA supply an eco-friendly procedure for the synthesis of some novel 5- pyrazolin-1,2,4-triazazolidine-3-ones or thiones through one-pot reaction of thiosemicarbazide (hydrazinecarbothioamide) and synthetized pyrazole carbaldehydes. These compounds were obtained in high yields in short reaction times. The catalyst could be easily recovered and reused for six cycles with almost consistent activity. The structures of the synthesized 5-pyrazolin-1,2,4-triazazolidine-3-ones or thiones were confirmed by ¹H NMR, ¹³C NMR and FTIR spectral data and elemental analyses. Conclusion: In conclusion, we have investigated NiFe2O4@SiO2nPr@amino glucose as a new, eco-friendly, inexpensive, mild and reusable catalyst for the synthesis of 5-pyrazolin-1,2,4-triazazolidine-3-ones or thiones. High yield, a simple workup procedure, adherence to the basics of green chemistry, environmental friendly and based on natural ingredients, ease of separation and recyclability of the magnetic catalyst and waste reduction are some advantages of this method.