Retracted: Synthesis of 2‐Arylisoindoline Derivatives Catalyzed by Reusable 1,2,4‐Triazole Iridium on Mesoporous Silica through a Cascade Borrowing Hydrogen Strategy

Abstract

Covalent attachment of a 1,2,4‐triazole iridium complex to mesoporous MCM‐41 generated a heterogeneous catalyst that was found to be effective in the synthesis of 2‐aryl isoindolines, quinolines, cyclic amines, and symmetrical secondary amines through a cascade borrowing hydrogen strategy. Interestingly, the supported heterogeneous iridium catalyst prepared from the 1,2,4‐triazole iridium complex and mesoporous MCM‐41 exhibited high catalytic activity in the preparation of 2‐aryl isoindoline derivatives and symmetrical secondary amines. The catalyst system is highly recyclable for at least five times. Besides the important effect of the triazole, iridium sites grafted on siliceous supports can act as multifunctional catalytic centers and thus greatly enhance the catalytic activity of the catalysts. Furthermore, mechanistic experiments revealed that the reaction is initiated by an initial alcohol dehydrogenation and promoted by an iridium hydride intermediate. Importantly, the direct detection of a diagnostic iridium hydride signal confirmed that the synthesis of 2‐aryl isoindolines occurs by a borrowing hydrogen process. This work provides an efficient example of isoindolines synthesis through a borrowing hydrogen strategy.

Accessing 2‐Aryl Quinolines via Acceptorless Dehydrogenation and Transfer Hydrogenation Under Base and Solvent‐Free Reaction Conditions

“…In the last decade, acceptorless dehydrogenation, borrowing hydrogen, and transfer hydrogenation strategies have gained popularity to overcome these challenges [15,16] . Owing to this, there are numerous reports on acceptorless dehydrogenative synthesis of quinolines utilizing homogenous catalytic system involving metals such as Co, [17] Cu, [18] Ir, [19] Fe, [20] Mn, [21] Ni, [22] Re, [23] Ru, [24] Zn, [25] and heterogeneous catalyst such as Co on C 3 N 4 , [26] CuO, [27] CuNiFeO, [28] Fe 2 O 3 , [29] CoFe 2 O 4 , [30] Ir on mesoporous silica, [31a] porous organic polymer supported Ir catalyst, [31b] covalent triazine framework supported Ir complex, [31c] Pd on polymer support [32] . However, the synthesis of quinoline via transfer hydrogenation strategy remains less explored [33–36] .…”

Mild synthesis of isoxazoline derivatives via an efficient [4 + 1] annulation reaction of transient nitrosoalkenes and sulfur ylides

“…Subsequently, Xiao and co-workers have described highly efficient indole and indoline synthesis that relies on [4 + 1] reactions of stable sulfur ylides and aza-o-quinodimethane intermediate generated in situ 20,21 . As a part of our interest in the reactions with sulfur ylide 14,25 and developing efficient synthetic protcols towards the construction of biologically interesting heterocycles [34][35][36][37][38][39][40][41] , we envision that sulfur ylides would be the perfect C1 units to react with nitrosoalkene intermediates generated from α-bromooximes to afford isoxazoline derivatives (Fig. 1c), which are significant motifs existing in pharmaceutical and medicinal chemistry [42][43][44][45][46][47][48][49][50] .…”