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. 2024 Feb 6;15(11):4114-4120.
doi: 10.1039/d4sc00120f. eCollection 2024 Mar 13.

Tunable C-H functionalization and dearomatization enabled by an organic photocatalyst

Bohang An  1 , Hao Cui  1 , Chao Zheng  2 , Ji-Lin Chen  1 , Feng Lan  1 , Shu-Li You  2 , Xiao Zhang  1
Affiliations

Tunable C-H functionalization and dearomatization enabled by an organic photocatalyst

Bohang An et al. Chem Sci. .

Abstract

C-H functionalization and dearomatization constitute fundamental transformations of aromatic compounds, which find wide applications in various research areas. However, achieving both transformations from the same substrates with a single catalyst by operating a distinct mechanism remains challenging. Here, we report a photocatalytic strategy to modulate the reaction pathways that can be directed toward either C-H functionalization or dearomatization under redox-neutral or net-reductive conditions, respectively. Two sets of indoles and indolines bearing tertiary alcohols are divergently furnished with good yields and high selectivity. The key to success is the introduction of isoazatruxene ITN-2 as a novel photocatalyst (PC), which outperforms the commonly used PCs. The ready synthesis and high modulability of isoazatruxene type PCs indicate their great application potential.

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Conflict of interest statement

A patent has been filed on the use of isoazatruxenes and their derivatives in photocatalysis.

Figures

Scheme 1
Scheme 1. Tunable C–H functionalization and dearomatization.
Scheme 2
Scheme 2. Performance of various photocatalysts in C–H functionalization and characterization of ITNs.
Scheme 3
Scheme 3. Substrate scope for C–H functionalization.a,b aReaction conditions: a solution of ITN-2 (5.2 mg, 5.0 mol%) and 1 (0.2 mmol, 1.0 equiv.) in toluene (2.0 mL, 0.1 M) was irradiated by a 427 nm Kessil lamp (40 W) at room temperature under a nitrogen atmosphere for 4–36 h. bIsolated yield.
Scheme 4
Scheme 4. Substrate scope for dearomatization.a,b aReaction conditions: a solution of ITN-2 (5.2 mg, 5.0 mol%), 1 (0.2 mmol, 1.0 equiv.), HEH (0.3 mmol, 1.5 equiv.), and DMAP (2.4 mg, 10.0 mol%) in CH2Cl2 (2.0 mL, 0.1 M) was irradiated by blue LEDs (30 W) at room temperature under a nitrogen atmosphere for 12–48 h. bIsolated yield. Ratios of diastereoisomers were determined by crude 1H NMR analysis.
Scheme 5
Scheme 5. Gram-scale reaction.
Scheme 6
Scheme 6. Proposed mechanism.
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