Selective grignard addition to dialkyl oxalates: A flow chemistry approach

Abstract

During the production of an intermediate of a major product of Bayer CropScience Schweiz AG in Muttenz, Switzerland, a side compound is formed that lowers yield and removal requires intensive workup. In the reaction the Grignard reagent 2 reacts with dialkyl oxalate 3 to an α-keto ester 3 (Fig. 1). Currently a semi-batch operation mode is used (Fig. 2). Fig. 1 and 2: Simplified synthesis of desired compound 3 and formation of undesired side compound 4 and current batch process. A second addition (overreaction) of the Grignard reagent 2 to compound 3 can occur and the undesired side compound 4 is formed. The following potentials have been identified: - Increasing the yield would enhance the overall efficiency of the process. - Reduction of bis-alcohol (4) would be desirable for both, economic and environmental impact. - An optimized and simplified process would lead to more flexibility in the production plant of Bayer CropScience Schweiz AG in Muttenz.