Carbonylative Ring Expansion of Epoxides to β‐Lactones Using Inorganic Salt as Catalytic Species Precursor

Abstract

Transition‐metal‐catalyzed carbonylative transformation is a well‐established and indispensable tool in organic chemistry, partially due to that CO is a cheap and readily available C1‐building block. The β‐lactone products via carbonylative ring expansion of epoxide are particularly attractive, because they feature broad utility in organic and polymer chemistry. One of the major challenges for this promising reaction is the usage of toxic, moderately air sensitive, unstable and pyrophoric low‐valent cobalt catalysts. Inorganic salts feature high abundance in nature, and the generation of catalytic species from in situ reduction of divalent cobalt(II) salt has received intense attention, which avoids the unnecessary storage and transport of sensitive low‐valent cobalt compounds. Herein, we have employed this strategy for the selectively carbonylative ring expansion of epoxides under an extremely mild condition, e. g. 40 °C and 1 atm CO pressure. This method eliminates the usage of extremely sensitive cobalt carbonyl catalyst. In addition, this reaction is tolerant to a variety of epoxides, and up to 15 examples of β‐lactones with excellent functionality have been isolated in moderate to excellent yields and selectivity.