A one pot reaction cascade of in situ hydrogen peroxide production and lipase mediated in situ production of peracids for the epoxidation of monoterpenes

• Combination of lipase-mediated epoxidation with industrial anthraquinone process.
• AQ-process successfully optimized to gain good hydrogen peroxide yields.
• Epoxidation of 3 monoterpenes (limonene, α-pinene and 3-carene).
• No side reactions of products observed due to mild reaction conditions.

In this work, the epoxidation of monoterpenes in the presence of Candida antartica lipase B (CALB) by the in situ generation of peroxy acid was combined with the industrial anthraquinone (AQ) process of hydrogen peroxide production. The reaction cascade consists of two major steps: reduction of an AQ to its corresponding anthrahydroquinone (AHQ) followed by the reverse auto-oxidation step of AHQ to AQ yielding equimolar amounts of hydrogen peroxide. Temperatures for each of the steps, ratio of substrate to catalyst, possible inhibition of lipases by the AQ and reaction medium (a mixture of hydrophobic and hydrophilic solvents) to be used were investigated. By using this reaction cascade, the addition of large amounts of hydrogen peroxide was avoided and conversions to epoxides of up to 83 (±9)% for limonene, 76 (±8)% for α-pinene and 82 (±8)% for 3-carene were achieved within 16 h.

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