Ligand-free iridium-catalyzed regioselective C-H borylation of indoles

Computational Design of Ligands for the Ir-Catalyzed C5-Borylation of Indoles through Tuning Dispersion Interactions

The indole moiety is ubiquitous in natural products and pharmaceuticals. C-H borylation of the benzenoid moiety of indoles is a challenging task, especially at the C5 position. We have combined computational and experimental studies to introduce multiple noncovalent interactions, especially dispersion, between the substrate and catalytic ligand to realize C5-borylation of indoles with high reactivity and selectivity. The successful computational predictions of new ligands should be suitable for ligand design in other transition-metal catalyzed reactions.

Recent advances in theoretical studies on transition-metal-catalyzed regioselective C-H functionalization of indoles

Indole compounds are widely found in natural products and drug candidates. The transition-metal-catalyzed regioselective C-H bond functionalization of indoles as the most efficient method for the synthesis of various functionalized indoles has been extensively studied in the past two decades due to its advantages of step economy and atom economy. In general, the catalysts included the transition-metals (Pd, Rh, Ru, Cu, Co, Fe, Zn, and Ga) and these reactions were accomplished with a remarkably wide range of coupling reagents for construction of various C-C and C-X (X = N, O, S) bonds. However, the general and important rules of the regioselectivity are not clear to date. Therefore, a comprehensive analysis through previous reported theoretical studies on transition-metal-catalyzed regioselective C-H bond functionalization of indoles was crucial and significant. In this review, we found that when the C-H bond activation process was the rate-determining step, the regioselectivity ordinarily occurred at the C7 or C4 positions (on benzene ring), and otherwise, the regioselectivity often occurred at C2 position (on pyrrole ring). For indoline substrates, the C-H bond functionalization occurred at the benzene ring. General rules of the regioselectivities for transition-metal-catalyzed C-H bond functionalization of indoles. This review collects major advances in the transition-metal-catalyzed C-H bond functionalization of indoles and indolines.

On the application of 3d metals for C-H activation toward bioactive compounds: The key step for the synthesis of silver bullets

Several valuable biologically active molecules can be obtained through C-H activation processes. However, the use of expensive and not readily accessible catalysts complicates the process of pharmacological application of these compounds. A plausible way to overcome this issue is developing and using cheaper, more accessible, and equally effective catalysts. First-row transition (3d) metals have shown to be important catalysts in this matter. This review summarizes the use of 3d metal catalysts in C-H activation processes to obtain potentially (or proved) biologically active compounds.