Direct α-Acylation of Alkenes via N-Heterocyclic Carbene, Sulfinate, and Photoredox Cooperative Triple Catalysis

Kun Liu and Armido Studer*

*Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, 48149 Münster, Germany, Email: studeruni-muenster.de

K. Liu, A. Studer, J. Am. Chem. Soc., 2021, 143, 4903-4909.

DOI: 10.1021/jacs.1c01022

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Abstract

Direct α-C-H acylation of various alkenes with aroyl fluorides using NHC, sulfinate, and photoredox cooperative triple catalysis provides α-substituted vinyl ketones in good yields with excellent functional group tolerance.

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proposed mechanism

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General procedure for the α-acylation of aryl olefins

To a Schlenk tube, Ru(bpy)₃(PF₆)₂ (1.9 mg, 0.00225 mmol), carbene catalyst B (9.5 mg, 0.03 mmol), sodium 4-chlorobenzene sulfinate (9.0 mg, 0.045 mmol) and Cs₂CO₃ (24.5 mg, 0.075 mmol) were added. Then, the reaction tube was evacuated and backfilled with argon for three times. Subsequently, styrene (0.15 mmol), 1-methyl-1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (MTDB, 29.8 mg, 0.195 mmol), acyl fluoride (0.375 mmol, if solid, it should be added at the beginning) and MeCN (1.5 mL) were added. The resulting mixture was degassed under vacuum for two times and then the reaction mixture was irradiated with a 23 W CFL at room temperature for 24 hours. After that, the residue was purified by silica gel chromatography using a mixture of pentane/Et₂O as an eluent to get the desired product.

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Key Words

acylation, organocatalysis, photochemistry

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ID: J48-Y2021