A High-Yield and Cost-Effective Synthesis of Spirotetramat
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High-Yield and Cost-Effective Synthesis of Spirotetramat Guiqing Xua, Jiahao Wanga, Yingjie Zhoua, and Longfei Maoa,* a
Henan Engineering Research Center of Chiral Hydroxyl Pharmaceutical, Henan Normal University, Xinxiang, 453007 China *e-mail: [email protected] Received March 29, 2020; revised April 4, 2020; accepted April 18, 2020
Abstract—cis-8-Methoxy-1,3-diazaspiro[4.5]decane-2,4-dione, the key intermediate in the synthesis of spirotetramat, was synthesized by catalytic hydrogenation, oxidation, and Bucherer–Bergs reaction with 4-methoxycyclohexan-1-one as raw material. Spirotetramat was obtained in an overall yield of 20.4% by a multi-step reaction sequence including hydrolysis, esterification, acylation, intramolecular condensation, and O-acylation. The advantages of the proposed method are mild conditions, simple operation, and good to excellent yields in each step. Keywords: cis-8-methoxy-1,3-diazaspiro[4.5]decane-2,4-dione, spirotetramat, synthesis
DOI: 10.1134/S1070428020100176 INTRODUCTION Spirotetramat, cis-3-(2,5-dimethylphenyl)-8-methoxy-2-oxo-1-azaspiro[4.5]dec-3-en-4-yl ethyl carbonate (10), is a second-generation insecticide developed by Bayer CropScience (Germany) under the brand name Movento [1]. Spirotetramat has a good efficacy and safety for crops. Its unique two-way internal absorption and transport properties enable spirotetramat to be transported to any part of the plant, which can effectively prevent egg hatching and larval development of pests on roots and leaves. In addition, spirotetramat exhibits a long-lasting efficacy, and it can effectively control pests for as long as two months [2]. Furthermore, the characteristics of spirotetramat such as high activity, low dosage, broad-spectrum insecticidal efficacy, and environmental safety meet China’s pesticide requirements [3]. Therefore, spirotetramat has prominent applications and market prospects. In this work, we intended to improve the procedure for the synthesis of spirotetramat by optimizing the conditions and reducing the synthetic cost.
Two main synthetic routes of spirotetramat have been reported (Scheme 1). In the first route, 1-amino4-methoxycyclohexane-1-carbonitrile (1) and 2,5-dimethylphenylacetyl chloride (2) were used as starting materials. The target compound was obtained by N-acylation, cyano hydrolysis, esterification, intramolecular cyclization, and final O-acylation with ethyl chloroformate [4–11]. However, spirotetramat obtained by this method is a racemic mixture that needs to be separated, which reduces the yield and increases the cost. In the second method, spirotetramat can be obtained via esterification, acylation, cyclization, and nucleophilic substitution reaction from cis-1-amino-4methoxycyclohexane-1-carboxylic acid (6) [12–17]. This method could avoid isomer separation of isomers, but the disadvantage is that the raw material is more expensive. In terms of yield and necessity of isomer separation, the second method is advantageous over the first, so we chose to optimize the process based on the sec
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