A Chemoselective Polarity‐Mismatched Photocatalytic C(sp³)−C(sp²) Cross‐Coupling Enabled by Synergistic Boron Activation**

Abstract

We report the development of a C(sp3)–C(sp2) coupling reaction using styrene boronic acids and redox‐active esters under photoredox catalysis. The reaction proceeds through an unusual polarity‐mismatched radical addition mechanism that is orthogonal to established processes. Synergistic activation of the radical precursor and organoboron are critical mechanistic events. Activation of an N‐hydroxyphthalimide (NHPI) ester by coordination to boron enables electron transfer, with decomposition leading to a nucleofuge rebound, activating the organoboron to radical addition. The unique mechanism enables chemoselective coupling of styrene boronic acids in the presence of other alkene radical acceptors. The scope and limitations of the reaction, and a detailed mechanistic investigation are presented.

Visible-light-induced decarboxylative cascade cyclization of acryloylbenzamides with N-hydroxyphthalimide esters via EDA complexes

“…1 Among the developed methods, photocatalytic decarboxylation of alkyl NHP esters has been widely used for preparing functional compounds, 2 as the liberation of phthalimide and CO 2 as by-products indicates a strong driving force for the reaction, forming alkyl radical intermediates to build more valuable chemicals. Impressive progress has been achieved in this field by using transition-metal 3 or organic dye-based photoredox catalysts. 4 Recently, the introduction of a phosphine/iodide-based photoredox system to catalyze decarboxylative alkylative reactions with alkyl NHP esters has aroused much attention due to the advantages of easy accessibility and low cost compared with transition-metal complexes or organic dye-based photocatalysts.…”

Modular Synthesis of Complex Benzoxaboraheterocycles through Chelation-Assisted Rh-Catalyzed [2 + 2 + 2] Cycloaddition

“…, Suzuki–Miyaura, , Chan–Lam, , and Hayashi , reactions). Further applications are broad-ranging including within photocatalysis − and materials chemistry; − however, the rise of boron in pharmaceutical design is of particular significance. − …”