Visible light-triggered selective C(sp2)-H/C(sp3)-H coupling of benzenes with aliphatic hydrocarbons

Abstract

The direct and selective coupling of benzenes with aliphatic hydrocarbons is a promising strategy for C(sp2)-C(sp3) bond formation using readily available starting materials, yet it remains a significant challenge. In this study, we have developed a simplified photochemical system that incorporates catalytic amounts of iron(III) halides as multifunctional reagents and air as a green oxidant to address this synthetic problem. Under mild conditions, the reaction between a strong C(sp2)-H bond and a robust C(sp3)-H bond has been achieved, affording a broad range of cross-coupling products with high yields and commendable chemo-, site-selectivity. The iron halide acts as a multifunctional reagent that responds to visible light, initiates C-centered radicals, induces single-electron oxidation to carbocations, and participates in a subsequent Friedel-Crafts-type process. The gradual release of radical species and carbocation intermediates appears to be critical for achieving desirable reactivity and selectivity. This eco-friendly, cost-efficient approach offers access to various building blocks from abundant hydrocarbon feedstocks, and demonstrates the potential of iron halides in sustainable synthesis.

Cu(II)-Mediated direct 18F-dehydrofluorination of phosphine oxides in high molar activity

“…Thus, we hypothesized that this fluorination mechanism might involve a radical pathway. To test this hypothesis, radical trapping experiments were performed using the commonly employed radical capture agents, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and 2,6-di- tert -butyl-4-methylphenol (BHT), known for effectively capturing free radicals in chemical reactions (Li et al 2023 ; Ye et al 2023 ). Surprisingly, the conversion of product 1 remained at 100% when 3.0 equivalents of TEMPO or BHT were added under standard condition.…”

Csp2–H functionalization of phenols: an effective access route to valuable materials via Csp2–C bond formation

“…Mechanistic studies revealed the multifunctional role of the iron halide, which responds to visible light, initiates C-centered radicals, induces single-electron oxidation to carbocations, and engages in a subsequent Friedel-Cras-type process (Scheme 5). 58 Diazo-compounds have emerged as effective phenolic alkylating agents through transition-metal catalysed carbene transfer reactions. They have become a powerful synthetic tool for accessing regio-and chemo-selective aromatic compounds via Csp 2 -H bond functionalization, ensuring step-and atomeconomy.…”

“…Mechanistic studies revealed the multifunctional role of the iron halide, which responds to visible light, initiates C-centered radicals, induces single-electron oxidation to carbocations, and engages in a subsequent Friedel–Crafts-type process ( Scheme 5 ). 58 …”

Manganese Complexes with Consecutive Mn(IV) → Mn(III) Excitation for Versatile Photoredox Catalysis

“…In terms of the arene reaction partner, various benzene derivatives were systematically explored. Monosubstituted benzenes with electron-withdrawing group like −CF 3 (36), or electron-donating groups [e.g., −OMe (37), −SMe (38), −Me (39), −tBu (40), and −SiMe 3 (41)], were all welltolerated, yielding 54 to 72% yields with moderate siteselectivities ranging from 1.6:1 to 4:1. Disubstituted (42−51) and trisubstituted benzenes (52−55) also smoothly participated in this process, with some cases displaying exclusive regioselectivity.…”

“…Our group dedicated to developing cost-effective photochemical synthetic methods, propelled by the use of transition metal catalysts. − Drawing from our research experiences and inspired by relevant literature, − we postulated that manganese complexes with promising visible light response and elongated excited-state lifetimes could be attained through careful selection of complex frameworks and tailored modification of binding ligands. Central to this approach is the integration of robust σ-donor ligands to amplify ligand field strength, as evidence by increased ligand field parameters (10 Dq). − Fundamentally, the nature of excited-state electronic configurations is governed by the intricate balance between the 10 Dq parameter and the Racah B factor, reflecting the degree of covalency in metal–ligand bonds and playing a pivotal role in modulating nephelauxetic effects. − By meticulous adjustment of metal–ligand covalency to diminish the Racah B value, enhanced delocalization of d-electrons around the manganese nucleus becomes attainable, a strategy that reduces electron–electron repulsion and is instrumental in achieving the desired prolongation of excited-state lifetimes (Figure B).…”