In this review, we summarise the recent applications of pyridinium salts in radical-mediated difunctionalization of alkenes. Pyridinium salts are a privileged class of compounds that show great utility in natural...

The trifluoromethylselenyl group (CF3Se) has become an emerging fluorinated moiety in synthetic chemistry due to its high Hansch lipophilicity parameter and strong electron-withdrawing effect. The trifluoromethylselenolation is hampered by limited synthetic methods and related reagents. Herein, we designed and synthesized the new electrophilic trifluoromethylselenolation reagents, trifluoromethyl selenoxides, which are easy to prepare and easy-to-handle and are not moisture or air sensitive. The selenoxides are successfully applied to metal-free C–H trifluoromethylselenolation of a series of (hetero)­arenes.

The introduction of trifluoromethylchalcogen group (CF 3 O, CF 3 S and CF 3 Se) has attracted growing attention in the field of modern organofluorine chemistry. Compared with the CF 3 S and CF 3 O chemistry, methods for trifluoromethylselenolation are much less developed owing to the limited availability of CF 3 Se transfer reagents and synthetic methods. The CF 3 Se group introduces promising lipophilicity (Hansch-Leo parameter = 1.29) and strong electron-withdrawing effect (Hammett constants σ m = 0.44, σ p = 0.45) which are important parameters for the development of new pharmaceutically relevant compounds. Traditionally, the CF 3 Se compounds were synthesized by the nucleophilic trifluoromethylation of diselenides and selenocyanates, which suffered from harsh conditions and/or limited substrates scope. Compared with the indirect methods, the direct formation of CÀ SeCF 3 constitutes is a more efficient approach. In recent years, new reagents and methods were developed which enabled the incorporation of the trifluoromethylselenyl group directly under mild conditions, specifically in transition metal catalysis and photoredox catalysis. In this review, we will focus on direct trifluoromethylselenolation strategies based on the development of new trifluoromethylselenolation reagents and methods. 2.1. MÀ SeCF 3 (M=Hg, Cu, Ag) 2.2. [(bpy)CuSeCF 3 ] 2 2.3. (Me 4 N)SeCF 3 2.4. BTÀ SeCF 3 3. Electrophilic Trifluoromethylselenolation Reagents 3.1. In situ formed CF 3 SeCl from BnSeCF 3 + SO 2 Cl 2 3.2. TsSeCF 3 4. Miscellaneous 5. Conclusions

Here we report a mild and general method for the trifluoromethylthiolation of aldehydes using N-trifluoromethylthiosaccharin as the CF3S radical source and sodium decatungstate (NaDT) as the photocatalyst. This reaction proceeds via hydrogen atom abstraction by photoactivated DT and features good functional groups and substrate tolerance. Generally, electron-rich aldehydes demonstrate better reactivity than electron-deficient ones and good selectivity is observed for the trifluoromethylthiolation of aldehydic C–H bonds over tertiary and benzylic C–H bonds. Preliminary mechanistic studies have shown that a free radical process is involved.

Based on fully analyzing the mechanism of Beckmann rearrangement reaction, protonated amino functional mesoporous silica materials HAF-SBA-15 were obtained via acidizing amino functional mesoporous silica. The binding force between hydroxamic hydroxyl group and N was synergistically weakened by the coordination bond formed by proton hydrogen in HAF-SBA-15, lone pair electrons in hydroxyl hydroxoxoxime and hydrogen bonds formed between N, H and O. It synergistically weakenef the binding force between oxime hydroxyl and N, accelerated the departure of oxime hydroxyl and the formation of carbon positive ions,, and promoted the Beckmann rearrangement reaction. Catalyzed by HAF-SBA-15, N-benzophenamide was synthesized via the Beckmann rearrangement of diphenyl-ketoxime. The results showed that the conversion rate of diphenyl-ketoxime is high and the obtained N-benzophenamide is pure. Furthermore, effect of solvent type, reaction temperature, and catalyst dosage on the Beckmann rearrangement of diphenyl-ketoxime was investigated, and the optimum reaction conditions were obtained. The results illustrated that the optimum reaction conditions are mild because Beckmann rearrangement of diphenyl-ketoxime was efficiently carried out at 50 ℃.