Development of Trifluoromethanesulfonic Acid-Immobilized Nitrogen-Doped Carbon-Incarcerated Niobia Nanoparticle Catalysts for Friedel-Crafts Acylation

Iron-Catalyzed Friedel-Crafts-type 3,5-Diacylation of Indoles

The exploration of remote functionalization of indoles is impeded by the inherently dominant reactivity intrinsic to the pyrrole moiety. Herein, we delineate a novel strategy facilitated by Lewis acid mediation, enabling the remote C-H functionalization, which culminates in the synthesis of an array of selectively functionalized indole derivatives, encompassing 3-trifluoroacetyl and 5-benzoyl motifs, utilizing trifluoroacetic anhydride and various acyl chlorides. Notably, the protocol exhibits versatility, as epitomized by the extension of C5-acylation to alkylation and sulfonation reactions. This methodology is distinguished by its exemplary regio- and chemo-selectivity, extensive substrate scope, commendable tolerance to a diverse array of functional groups, and the employment of comparatively mild reaction conditions.

Mechanism of Friedel-Crafts Acylation Using Metal Triflate in Deep Eutectic Solvents: An Experimental and Computational Study

In this paper, we develop a method for Friedel-Crafts acylation using metal triflate in deep eutectic solvents. Various metal triflates were tested and provided good to excellent yields of corresponding ketone products. The density functional theory calculation revealed the metal effects on the formation of active intermediate acylium triflate as well as the acidic condition. The metal triflate in the deep eutectic solvent can be recovered and reused with a little loss in the catalytic activity.

Regioselective Friedel-Crafts Acylation Reaction Using Single Crystalline and Ultrathin Nanosheet Assembly of Scrutinyite-SnO2

Peculiar physicochemical properties of two-dimensional (2D) nanomaterials have attracted research interest in developing new synthetic technology and exploring their potential applications in the field of catalysis. Moreover, ultrathin metal oxide nanosheets with atomic thickness exhibit abnormal surficial properties because of the unique 2D confinement effect. In this work, we present a facile and general approach for the synthesis of single crystalline and ultrathin 2D nanosheets assembly of scrutinyite-SnO₂ through a simple solvothermal method. The structural and compositional characterization using X-ray diffraction (Rietveld refinement analysis), high-resolution transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and so on reveal that the as-synthesized 2D nanosheets are ultrathin and single crystallized in the scrutinyite-SnO₂ phase with high purity. The ultrathin SnO₂ nanosheets show predominant growth in the [011] direction on the main surface having a thickness of ca. 1.3 nm. The SnO₂ nanosheets are further employed for the regioselective Friedel-Crafts acylation to synthesize aromatic ketones that have potential significance in chemical industry as synthetic intermediates of pharmaceuticals and fine chemicals. A series of aromatic substrates acylated over the SnO₂ nanosheets have afforded the corresponding aromatic ketones with up to 92% yield under solvent-free conditions. Comprehensive catalytic investigations display the SnO₂ nanosheet assembly as a better catalytic material compared to the heterogeneous metal oxide catalysts used so far in the view of its activity and reusability in solvent-free reaction conditions.