Current Organic Chemistry - Volume 29, Issue 13, 2025

Although a number of Lewis acids based on boron have been identified thus far, tris(pentafluorophenyl) borane [B(C6F5)3] (henceforth, BCF) has drawn the greatest interest from the synthetic chemistry community. Due to its commercial availability and thermal stability, BCF has been thoroughly investigated in organic and materials chemistry for its potential as a Lewis acid catalyst. The last two decades have witnessed the majority of BCF chemistry research in organic synthesis, and numerous novel catalytic reactivities are presently being studied. In this triennial update, which covers the period from 2021 to the present, we have thoroughly and critically reviewed the most representative applications of tris(pentafluorophenyl)borane in organic synthesis. Mechanistic studies are presented together with the scope of the catalyst.

A series of asymmetrical spirohomo- and methanofullerenes were synthesized for the first time in reactions of selective cycloaddition of adamantane diazo compounds to C60 fullerene in the presence of the catalyst Pd(PPh3)2Cl2. Adamantane diazoalkanes were obtained in situ in the oxidation reactions of adamantane hydrazones with manganese oxide MnO2. It has been established that the presence of adamantyl on the methylene bridge (in the case of symmetry of the spirocyclic fragment), methyl and ethyl substituents, or no substituents (in the case of asymmetry of the spirocyclic fragment) leads to the formation of exclusively [5,6]-open isomers (homofullerenes); when the hydrocarbon radical (butyl and nonyl radical) is extended on the methylene bridge of the asymmetric spirocyclic fragment, only [6,6]-closed isomers (methanofullerenes) are formed. All homofullerenes obtained in this work do not isomerize into the corresponding methanofullerenes under thermal conditions (180°C, 100 hours). Homofullerenes containing an adamantyl radical (in the case of symmetry of the spirocyclic fragment) or not containing substituents (in the case of asymmetry of the spirocyclic fragment) on the methylene bridge do not isomerize into the corresponding methanofullerenes under the influence of ultrasound (room temperature, 5 hours). For the first time, sonochemical isomerization of spirohomofullerenes containing electron-donating methyl and ethyl groups on the methylene bridge into methanofullerenes was carried out under mild conditions (1.5 hours, toluene, room temperature, air). Atmospheric oxygen does not affect the isomerization reaction. The presence of CCl4, which forms CCl3^● radicals during sonolysis, suppresses isomerization reactions, which indicates the participation of radical particles in the rearrangement process. A probable mechanism for the structural rearrangement of homofullerenes into methanofullerenes under the action of ultrasound is proposed.

To improve the activity of isatin-1,2,3-triazole hybrids as anti-cancer agents, new derivatives of isatin-thiosemicarbazone-1,2,3-triazoles 9-16 were designed and synthesized via the condensation of isatin-1,2,3-triazole hybrids 1-8 with thiosemicarbazide. Spectral and elemental analysis confirmed the structure of the prepared derivatives 9-16. Also, as anticancer agents, the latter derivatives were screened against three human cancerous cell lines: human lung fibroblast (WI38), colorectal carcinoma colon cancer (HCT-116), and mammary gland breast cancer (MCF-7). Doxorubicin, a standard control, was used to compare viable cell percentages and IC50 values. In general, derivatives 12 and 16 revealed a higher potency against the three human cancerous cell lines. Finally, the molecular descriptors of compounds 12 and 16 were correlated with their observed cytotoxicity.

In this study, a simple, mild, and environmentally friendly process was used for the pseudo-seven component reaction between readily available benzene-1,3,5-tricarboxylic acid, isocyano-cyclohexane, and various aldehydes. This rapid method produced the tris-cyclohexylamino-oxo-benzene-1,3,5-tricarboxylates in relatively acceptable and more reasonable reaction times (10-15 min) and high achievable efficiencies (85-95%) by employing a Passerini reaction. Water was used as an eco-friendly and low-cost solvent for the green synthesis of benzene tris-carboxamides. The reactions were carried out via a Passerini approach at 50℃ for relatively shorter reaction times. The antibacterial action of the synthetic tris-carboxamides was investigated, and some of them gave satisfactory and promising antibacterial results. Target tris-Passerini molecules recrystallized from 96% EtOH. The structures of the resulting molecules were evaluated and confirmed with the help of spectral data and elemental analyses.