Transition-Metal-Free C–C, C–O, and C–N Cross-Couplings Enabled by Light

Abstract

Transition-metal-catalyzed cross-couplings to construct C–C, C–O, and C–N bonds have revolutionized chemical science. Despite great achievements, these metal catalysts also raise certain issues including their high cost, requirement of specialized ligands, sensitivity to air and moisture, and so-called “transition-metal-residue issue”. Complementary strategy, which does not rely on the well-established oxidative addition, transmetalation, and reductive elimination mechanistic paradigm, would potentially eliminate all of these metal-related issues. Herein, we show that aryl triflates can be coupled with potassium aryl trifluoroborates, aliphatic alcohols, and nitriles without the assistance of metal catalysts empowered by photoenergy. Control experiments reveal that among all common aryl electrophiles only aryl triflates are competent in these couplings whereas aryl iodides and bromides cannot serve as the coupling partners. DFT calculation reveals that once converted to the aryl radical cation, aryl triflate would be more favorable to ipso substitution. Fluorescence spectroscopy and cyclic voltammetry investigations suggest that the interaction between excited acetone and aryl triflate is essential to these couplings. The results in this report are anticipated to provide new opportunities to perform cross-couplings.

Recent Advanced Materials for Electrochemical and Photoelectrochemical Synthesis of Ammonia from Dinitrogen: One Step Closer to a Sustainable Energy Future

“…[200] Also in early 2019, Liu et al performed computational studies on single boron atoms on a series of 2D materials and found that the graphene and h-MoS 2 are the most-promising supports for boron-based SAC system. [201] From all these studies, we find that the performance of SACs is a synergic result between single metal atoms and supports. Consequently, more computational studies are required to accumulate data to facilitate experimental efforts in searching for the optimal SAC system.…”

Theoretical Screening of Single Transition Metal Atoms Embedded in MXene Defects as Superior Electrocatalyst of Nitrogen Reduction Reaction

“…[6,12] Single atom catalysts (SACs) have become one of the hottest topics in heterogeneous catalysis. [12][13][14][15][16][17][18][19][20][21] The atomically dispersed metal on a substrate is highly unsaturated and thus exhibits outstanding activity. The strong interaction between the single atom and the substrate can effectively anchor the single atom and prevent aggregation to form metal cluster.…”

Atomic Modulation, Structural Design, and Systematic Optimization for Efficient Electrochemical Nitrogen Reduction

“…(Figure 3d). [42,57,64] In addition, unsaturated sites generated by the amorphous structures of carbon, and defects such as carbon [65] and nitrogen vacancies ( Figure 3e) [58] also contribute to the effective adsorption/activation of dinitrogen. Although tremendous progress has been made in recent years, the rules for tailoring active sites/centers toward effective guiding design of highly active electrocatalysts for NRR have not been outlined.…”

“…Boron is another high-profile element for doping in carbon materials. [64,74] In contrast with N-doped carbon materials, B doping leads to the polarization of the BC σ-bond and induces a positive charge on the boron atom owing to the lower electronegativity of boron (2.04) as compared to that of carbon (2.55). Moreover, since N 2 is a weak Lewis base, it is sufficient to generate a Lewis acid electrocatalytic site with an unoccupied orbital by boron doping to bind N 2 (Figure 4b).…”