Photoinduced Transition-Metal-Free Chan-Evans-Lam-Type Coupling: Dual Photoexcitation Mode with Halide Anion Effect

Zijun Zhou, Jeonguk Kweon, Hoimin Jung, Dongwook Kim, Sangwon Seo* and Sukbok Chang*

*Department of Chemistry, Korea Advanced Institute of Science & Technology (KAIST), Daejeon 34141, South Korea, Email: s.seokaist.ac.kr, sbchangkaist.ac.kr

Z. Zhou, J. Kweon, H. Jung, D. Kim, S. Seo, S. Chang, J. Am. Chem. Soc., 2022, 144, 9161-9174.

DOI: 10.1021/jacs.2c03343

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Abstract

A photoinduced transition-metal-free C(aryl)-N bond formation between 2,4,6-tri(aryl)boroxines or arylboronic acids and 1,4,2-dioxazol-5-ones (dioxazolones) provides N-arylamides under mild conditions. Chloride anions, either generated in situ by photodissociation of the chlorinated solvent or added separately as an additive, were found to play a critical cooperative role.

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proposed mechanism

Substrate scope investigation using 2,4,6-tri(aryl)boroxines

General Procedure A: In a glovebox, to an oven-dried screw-capped vial equipped with a triangular-shaped stirring bar were added dioxazolone (0.1 mmol), 2,4,6-tri(aryl)boroxine (0.08 mmol, 0.8 equiv), and anhydrous CH₂Cl₂ (0.2 mL, 0.5 M) under an argon atmosphere. The resulting solution was stirred for 12 h under 365 nm light irradiation using Penn photoreactor (LED power = 100%, fan speed = 6800 rpm, strring = 1000 rpm). The crude reaction mixture was directly subjected to silica column chromatography to provide the desired N-arylamide products (eluent: CH₂Cl₂/Acetone, 100:0 to 90:10).

General Procedure B: In a glovebox, to an oven-dried screw-capped vial equipped with a triangular-shaped stirring bar were added dioxazolone (0.1 mmol), 2,4,6-tri(aryl)boroxine (0.08 mmol, 0.8 equiv), and anhydrous CH₂Cl₂ (0.2 mL, 0.5 M) under an argon atmosphere. The resulting solution was stirred for 20 h under 420 nm light irradiation using Penn photoreactor (LED power = 100%, fan speed = 6800 rpm, strring = 1000 rpm). The crude reaction mixture was directly subjected to silica column chromatography to provide the desired N-arylamide products (eluent: CH₂Cl₂/Acetone, 100:0 to 90:10).

Key Words

amidation, anilines, photochemistry

ID: J48-Y2022