Synthesis of ketones, especially diaryl ketones, is attractive, since this functional group is present in a variety of pharmaceutical molecules and materials. Although a number of methods have been reported, such as Friedel-Crafts acylation, they suffer from drawbacks, for example the use of CO gas or stoichiometric amounts of metals.
Xiao-Feng Wu, Zhejiang Sci-Tech University, Hangzhou, China, and colleagues have developed a Pd-catalyzed carbonylative Suzuki coupling of aryl halides under CO gas-free conditions. The reaction utilizes formic acid as the CO source with acetic anhydride as an additive. Using Pd(OAc)2 in combination with PPh3, a number of aryl iodides were coupled with phenylboronic acids.
The reaction displays high tolerance of functional groups, including cyano groups and unprotected primary amines. Heteroaromatics, such as thiophene and pyridine, and aryl bromides could also be used. The team proposed a carbonylation mechanism where CO is produced in situ from acetic formic anhydride, which is obtained by the reaction of formic acid and acetic anhydride.
- A Convenient Palladium-Catalyzed Carbonylative Suzuki Coupling of Aryl Halides with Formic Acid as the Carbon Monoxide Source,
Xinxin Qi, Li-Bing Jiang, Hao-Peng Li, Xiao-Feng Wu,
Chem. Eur. J. 2015.