Selective Transformation of Strychnine and 1,2-Disubstituted Benzenes by C–H Borylation

Mechanistic Origins of Regioselectivity in Cobalt-Catalyzed C(sp2)-H Borylation of Benzoate Esters and Arylboronate Esters

“…[25][26][27][28][29][30] Selective borylation at the site para to a substituent has proven particularly challenging, with limited strategies for this outcome (Scheme 1B) including the use of exceptionally large phosphine ligands or Lewis acid co-catalysts. [31][32][33] An example of para-selective borylation of benzoate esters employed a unique quinolyl-substituted bipyridine ligand engaged in a secondary-substrate interaction involving a bridging alkali metal. 34 Recently, the laboratories of Smith and Phipps independently introduced a strategy utilizing tight substrate anion-ammonium ion pairs as a means of blocking most of the sterically accessible C(sp 2 )-H bonds on the substrate to favor borylation para to a given substituent.…”

Metal-catalysed C–H bond activation and borylation

“…In 2020, Itami and Segawa further reported 223 a remote C–H borylation method using a modified bulky diphosphine ligand ( L46 ) under iridium-catalysed conditions to achieve C3-selective C–H borylation of strychnine (Scheme 110). The functionalization of complex natural products, pharmaceuticals, and π-conjugated systems have sustained appreciable attention in recent years, mainly in the field of drug discovery.…”

Recent Trends in Group 9 Catalyzed C–H Borylation Reactions: Different Strategies To Control Site-, Regio-, and Stereoselectivity

“…In this context, Itami and co-workers reported the Ir-catalyzed highly C3-selective C–H borylation of strychnine, which is among the most famous natural products and displays a high degree of structural complexity (Scheme 26 A). 75 The molecule contains a tertiary amine, amide, alkene, ether, and indoline moieties with six asymmetric carbon atoms. The correct choice of ligand, in combination with an iridium source, enables the C3-selective borylation of strychnine with moderate selectivity (C3:C2, 73:27), which is driven by steric effects.…”