Current Organic Synthesis - Volume 19, Issue 4, 2022

A convenient, efficient, and general procedure for the synthesis of diaryl diselenides has been developed by the reaction of aryl diazonium tetrafluoroborates and potassium selenocyanate on the surface of alumina under ball-milling in the absence of any solvent, transition metal catalyst, and base in room temperature. A wide range of functionalized diaryl diselenides are obtained in high purity and high yield by this procedure. Background: Synthesis of diaryl diselenides was restricted into only a few Cu-catalyzed C-Se cross-coupling protocols where the use of ligands, high reaction temp, long reaction time were required. Objectives: The objective of this study is to achieve a sustainable protocol for the synthesis of diaryl diselenides. Method: Reaction of aryl diazonium fluoroborate with KSeCN was successfully performed under ball milling in the absence of any transition metal catalyst, ligands, base, and external heating to get diaryl diselenides. Results: A library of diaryl diselenides were obtained in good yields with different functional groups. Conclusion: First transition metal free protocol for the synthesis of diaryl diselenides has been developed successfully.

The investigation of the procedures for the multi-component synthesis of heterocycles has attracted the interest of organic and medicinal chemists. The use of heterogeneous catalysts, especially transition metal catalysts in organic synthesis, can provide a new, improved alternative to traditional methods in modern synthetic chemistry. The main focus is on the utilization of silver as a catalyst for the multi-component synthesis of heterocyclic compounds. The present review describes some important reported studies for the period of 2010 to 2020. Conclusion: The present review addresses some of the important reported studies on multicomponent synthesis of heterocycles in the period of 2010-2020. These approaches were performed under classical and nonclassical conditions, using Ag salts, Ag NPs, Ag on the support, Ag as cocatalysts with other transition metals, ionic liquids, acidic or basic materials. Most of the reported reactions were performed under solvent-free conditions or in green solvents and the utilized catalysts were mostly recyclable. The main aim of the present review is to provide the organic chemists with the most appropriate procedures in the multi-component synthesis of desired heterocycles using silver catalysts.

Background: Tubulysins, linear tetrapeptides, show extraordinary cytotoxicity against various cancer cells, with IC50 values in the nano or picomolar range. Due to their extremely vigorous anti-proliferative and antiangiogenic characteristics, tubulysins exhibit captivating prospects in the development of anticancer drugs. This review focuses on diverse routes for the total synthesis of natural and synthetic tubulysins as well as their fragments. Objective: The purpose of this review is to present the synthetic strategies for the development of antitumor agents, tubulysins. Conclusion: A range of synthetic pathways adopted for the total synthesis of tubulysins and their fragments have been described in this review. Synthesis of fragments, Tuv, Tup, and Tut can be accomplished by adopting appropriate strategies, such as Manganese-mediated synthesis, Ireland-Claisen rearrangement, Mukaiyama aldol reaction, Mannich process, etc. Tubulysins B, D, U, V, and N¹⁴-desacetoxytubulysin H have been prepared through Mitsunobu reaction, tertbutanesulfinamide method, Tandem reaction, aza-Barbier reaction, Evans aldol reaction, C-H activation strategies, etc. The remarkable anticancer potential of tubulysins toward a substantiate target makes them prominent leads for developing novel drugs against multidrug-resistant cancers.

Constituted by ions, ionic liquids (ILs) are evolving as greener solvents for many organic syntheses. Due to their high solvent power and low volatility, ionic liquids are serving as an environment- friendly substitute to conventional volatile organic solvents. The present review introduces ionic liquids as an insight into the diverse recent applications of ILs in organic synthesis.

Background: A series of new pyrimidines and thiazoles containing camphor moiety were synthesized under both conventional and microwave irradiation techniques. Methods: The condensation of camphor either with aminoguanidine or thiosemicarbazide gives the camphor hydrazine carboximidiamide 2 and the camphor thiosemicarbazone 3, respectively. Refluxing of 3 with chloroacetonitrile afforded the camphor thiazol-4-imine 4. Compounds 2 and 4 were used as precursors for the synthesis of target products. Results: The reaction of 2 with different species such as arylidene malononitrile, acetylacetone, and ethyl acetoacetate gave the corresponding camphor pyrimidine derivatives 5a,b-7 while refluxing of compound 4 with different reagents e.g. aldehydes, isatin, ninhydrin, acetic anhydride, benzene sulphonyl chloride, and p-nitro-benzoyl chloride afforded the camphor thiazole derivatives 8a-d- 13, respectively. Conclusion: A comparison between the conventional and the eco-friendly microwave irradiation methods occurred during the synthesis of the same compounds, and the latter proved to be more efficient. The elemental analysis, FT-IR, ¹H NMR, ¹³C NMR, and Mass spectra confirm the structures of the obtained new compounds. The potential use of some selected derivatives as antimicrobial agents was investigated and gave promising results.