Imidazolium-Based Ionic Liquid: An Efficient, Normalized, and Recyclable Platform for Rh(III)-Catalyzed Directed C–H Carbenoid Coupling Reactions

Abstract

The ionic liquid [BMIM]­[NTf2] was developed as an ideal medium in which Rh­(III)-catalyzed directed C–H carbenoid coupling reactions can be conducted efficiently and sustainably. More significantly, the ionic liquid can not only achieve the recycle of catalyst system but also improve the efficiency of catalyst, presenting that carbenoid coupling reactions can be accomplished at room temperature within a short period of time. Thus, this work would be useful in expanding applications of C–H activation strategies as tools for assembling novel organic molecules.

Synthesis of 1,2-Benzothiazines via C–H Activation/Cyclization in a Recyclable, Mild System

“…23,24 In addition, ILs possess good solvating capacities for various organic and inorganic substrates because of their potency in establishing ions and van der Waals interactions with solutes. 25 Combining our previous works on C−H cyanation 27 /amidation 28 /alkylation 29 1c). In this method, diazo compounds, alkynes, and sulfoxonium ylides serve as coupling partners to afford varieties of 1,2benzothiazines.…”

“…Ionic liquids (ILs), in which the ions are poorly coordinated, are well-known for their unique properties such as negligible vapor pressure, high thermal stability, low toxicity, nonflammability, high polarity, and relatively high ionic conductivity. − ILs are considered as good alternatives to conventional volatile liquid solvents in synthetic reaction and separation, which served as an efficient and recyclable platform for C–H catalytic activation. , In addition, ILs possess good solvating capacities for various organic and inorganic substrates because of their potency in establishing ions and van der Waals interactions with solutes . Combining our previous works on C–H cyanation/amidation/alkylation of arene in ionic liquids under mild conditions (Scheme b), ILs are supposed to be beneficial for lowering the reaction temperature. Inspired by our previous works on C–H activation in ILs − and functionalization of NH-sulfoximines, − herein, we report rhodium-catalyzed C–H activation/cyclization of NH-sulfoximines in ionic liquids to synthesize diverse 1,2-benzothiazines under mild conditions without base or acid additives (Scheme c).…”

“…Combining our previous works on C–H cyanation/amidation/alkylation of arene in ionic liquids under mild conditions (Scheme b), ILs are supposed to be beneficial for lowering the reaction temperature. Inspired by our previous works on C–H activation in ILs − and functionalization of NH-sulfoximines, − herein, we report rhodium-catalyzed C–H activation/cyclization of NH-sulfoximines in ionic liquids to synthesize diverse 1,2-benzothiazines under mild conditions without base or acid additives (Scheme c). In this method, diazo compounds, alkynes, and sulfoxonium ylides serve as coupling partners to afford varieties of 1,2-benzothiazines.…”

An Efficient, Sustainable Rhodium‐Catalyzed and Ionic Liquid‐Mediated C−H Thiolation and Selenation of Acetanilide with Diaryl Disulfides and Diaryl Diselenides

“…ILs also have other unique merits, involving low vapor pressures, low melting points, negligible toxicities, excellent solubility for inorganic and organic compounds, high thermal and chemical stability [18] . Thus, till now, ILs have been successfully applied in cycloaddition, [19] cross‐coupling [17b,20] and C−H bond functionalization [17c,d,21] . Acetanilide is a useful building block in organic synthesis and medicinal chemistry, owing to it contained a weakly carbonyl directing group.…”

Practical Synthesis of Benzimidazo[1,2-a]quinolines via Rh(III)-Catalyzed C–H Activation Cascade Reaction from Imidamides and Anthranils

“…ILs with a series of advantages including low volatility, high thermal/chemical stability, and a wide electrochemical window, are considered as better substitutes to traditional solvents in organic chemistry . On the basis of our previous studies for developing ILs as the C–H activation platform, we then tried several ILs as the solvents (entries 5–8). Surprisingly, [BMIM]­BF 4 (1-butyl-3-methylimidazolium tetrafluoroborate) was suitable for this transformation, affording the desired product in 71% yield (entry 5).…”