Kilogram synthesis of pinoxaden

Abstract

An optimized kilogram‐scale synthetic route for pinoxaden was successfully developed. The key intermediate dimethyl 2‐(2,6‐diethyl‐4‐methylphenyl)malonate (19) was prepared from 2,6‐diethyl‐4‐methylaniline through diazotization reaction, Suzuki cross‐coupling reaction, and alcoholysis reaction in 59% yield over three steps in 97.3% purity. 1,4,5‐Oxadiazepane dihydrobromide (11) was obtained from diethylene glycol through esterification, cyclization, deprotection, and salification in 64% yield over three steps. Pinoxaden was given by aminolysis of 19 with 11, followed by acylation by pivaloyl chloride in 64% yield over two steps in 99.9% purity. Purification methods for the intermediates and the final product were developed.