Continuous Flow Epoxidation of Alkenes Using a Homogeneous Manganese Catalyst with Peracetic Acid

• Ailbhe A. Ryan^abc, Seán D. Dempsey^abc, Megan Smyth^a, Karen Fahey^b, Thomas S. Moody^ab, Scott Wharry^a, Paul Dingwall^c, David W. Rooney^c, Jillian M. Thompson^c, Peter C. Knipe^c, and Mark J. Muldoon^c

• ^aAlmac Group, Craigavon BT63 5QD, United Kingdom
• ^bArran Chemical Company, Roscommon N37 DN24, Ireland
• ^cQueen’s University Belfast, Belfast BT9 5AG, United Kingdom

Epoxidation of alkenes is a valuable transformation in the synthesis of fine chemicals. Described herein are the design and development of a continuous flow process for carrying out the epoxidation of alkenes with a homogeneous manganese catalyst at metal loadings as low as 0.05 mol%. In this process, peracetic acid is generated in situ and telescoped directly into the epoxidation reaction, thus reducing the risks associated with its handling and storage, which often limit its use at scale. This flow process lessens the safety hazards associated with both the exothermicity of this epoxidation reaction and the use of the highly reactive peracetic acid. Controlling the speciation of manganese/2-picolinic acid mixtures by varying the ligand:manganese ratio was key to the success of the reaction. This continuous flow process offers an inexpensive, sustainable, and scalable route to epoxides.

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