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Mechanochemical Synthesis of Ketones via Chemoselective Suzuki-Miyaura Cross-Coupling of Acyl Chlorides

Jin Zhang*, Pei Zhang, Yangmin Ma and Michal Szostak*

*Shaanxi University of Science and Technology, Xi'an 710021, China; Rutgers University, Newark, New Jersey 07102, United States Email: zhangjinsust.edu.cn, michal.szostakrutgers.edu

J. Zhang, P. Zhang, Y. Ma, M. Szostak, Org. Lett., 2022, 24, 2338-2343.

DOI: 10.1021/acs.orglett.2c00519


Abstract

A mechanochemical solvent-free acyl Suzuki-Miyaura cross-coupling enables a highly chemoselective synthesis of ketones from widely available acyl chlorides and boronic acids. This chemoselective acylation reaction is conducted in the solid state, in the absence of potentially harmful solvents, and for a short reaction time.

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General Procedure for Acyl C(O)-CI Cleavage Using a Ball Mill

Acyl chloride (0.2 mmol), phenylboronic acid (1.5 equiv), Pd(OAc)2 (5 mol%), PCy3HBF4 (6 mol%), and K3PO4 (1.0 equiv) were placed in a ball milling bowl (stainless, 5 mL) loaded with one grinding ball (stainless, diameter: 5 mm). The bowl was placed in the ball mill (Retsch MM400, 10 min at 30 Hz). After 10 min, the reaction mixture was diluted with EtOAc (10 mL), filtered, and concentrated. The sample was analyzed by 1H NMR (CDCl3, 400 MHz) to obtain selectivity, conversion and yield using internal standard and comparison with authentie sampies. Unless stated otherwise, purification by chromatography on silica gel afforded the title product.

General Procedure for High Temperature Ball Milling

The heat gun was fixed with clamps and placed directly above the ball milling bowl (distance between the heat gun and ball milling bowl: ca. 1 cm). First, one grinding ball (stainless, diameter: 5 mm) was loaded in a ball milling bowl (stainless, 5 mL or 10 mL). Then solid and liquid materials were added to the bowl. After the ball milling bowl was closed, the bowl was placed in the ball mill (Retsch MM400) and a heat gun was placed directly above the ball-milling bowl. The mechanochemical cross-coupling reactions were conducted while applying heated air to the outside of the milling bowl (the preset temperature at 200°C).


Key Words

Suzuki coupling, acylation, mechanochemistry, green chemistry


ID: J54-Y2022