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. 2022 Oct 25:10:1058596.
doi: 10.3389/fchem.2022.1058596. eCollection 2022.

Chemodivergent photocatalytic access to 1-pyrrolines and 1-tetralones involving switchable C(sp3)-H functionalization

Shijing Tu  1 , Zhongyu Qi  1 , Weicai Li  1 , Shiqi Zhang  2 , Zhijie Zhang  1 , Jun Wei  1 , Lin Yang  1 , Siping Wei  1 , Xi Du  3 , Dong Yi  1
Affiliations

Chemodivergent photocatalytic access to 1-pyrrolines and 1-tetralones involving switchable C(sp3)-H functionalization

Shijing Tu et al. Front Chem. .

Abstract

A chemodivergent photocatalytic approach to 1-pyrrolines and 1-tetralones from alkyl bromides and vinyl azides has been developed through chemoselectively controllable intermolecular [3 + 2] and [4 + 2] cyclization. This photoredox-neutral two-component protocol involves intermolecular radical addition and switchable distal C(sp3)-H functionalization enabled by iminyl radical-mediated 1,5-hydrogen atom transfer. Meanwhile, chemoselectivity between C(sp3)-N bond formation and C(sp3)-C(sp2) bond formation is precisely switched by photocatalysts (Ru(bpy)3(PF6)2 vs. fac-Ir(ppy)3) and additives (base vs. acid).

Keywords: 1-pyrrolines; 1-tetralones; [3+2] cyclization; [4+2] cyclization; hydrogen atom transfer.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

SCHEME 1
SCHEME 1
Photocatalytic access to 1-pyrrolines via iminyl radical-mediated cyclization.
SCHEME 2
SCHEME 2
Substrate scope with respect to [3 + 2] cyclization. Reaction conditions: 1 (0.2 mmol), 2 (0.5 mmol), Ru(bpy)3(PF6)2 (2 mol%), K2CO3 (0.3 mmol), CH2Cl2 (2 ml), 30 W blue LEDs, argon atmosphere, r.t., 9 h, in a sealed tube; isolated yields based on 1 after the chromatographic purification.
SCHEME 3
SCHEME 3
Substrate scope with respect to [4 + 2] cyclization. Reaction conditions: 1 (0.2 mmol), 2 (0.4 mmol), fac-Ir(ppy)3 (2 mol%), AcOH (0.2 mmol), CH2Cl2 (4 ml), 30 W blue LEDs, argon atmosphere, r.t., 9 h, in a sealed tube; isolated yields based on 1 after the chromatographic purification. rr: regioisomeric ratio.
SCHEME 4
SCHEME 4
Representative derivatizations.
SCHEME 5
SCHEME 5
Preliminary mechanistic studies.
SCHEME 6
SCHEME 6
Plausible reaction mechanism.
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