Study On The Synthesis Of Plant Growth Regulator Trinexapac-ethyl

Plant growth regulator (PGR) is a kind of pesticides regulating plant growth and development. Trinexapac-ethyl is an acylcyclohexadione PGR that inhibits the biosynthesis of gibberellin (GA1). Trinexapac-ethyl is of a wide range of applications and high research value In this paper, the synthetic method of trinexapac-ethyl and its intermediates were selected and optimized on the basis of relevant references.3,5-dihydroxybenzoic acid (DHB) was choosed as the starting material. The target product was obtained through hydrogenation reduction, esterification, hydrolysis, acylation and rearrangement reaction.3,5-dioxocyclohexanecarboxylic acid (DOC) was achieved by catalytic transfer hydrogenation(CTH) from3,5-dihydroxyhenzoic acid. Studies were carried out to determine proper conditions. Good yields(98.6%) of product was obtained at100℃with sodium formate as the hydrogen donor, and Pd/C as the catalysist. It required only2.5h for complete reaction using water as sovent when sodium fomate:DHB is1:1. The conversion of DHB was100%. The reaction was detected by Thin Layer Chromatography(TLC) instead of High Performance Liquid Chromatography(HPLC). This method is easy to operate. At the last of this part, the reaction mechanism was proposed based on the experiment and references.3-ethoxy-5-carboethoxy-2-cyclohexenone was prepared by new synthesis technology of one-pot method. Using ethanol as solvent. The effects of the component ratio, temperature, time on the reaction were discussed and the optimum technological conditions were obtained. The result is as follows:n(DOC):n(thionyl chloride):n(triethylamine) is1:2:3, reaction time is3h, reaction temperature is50℃. Ethyl3,5-dioxocyclohexanecarboxylate was obtained from3-ethoxy-5-carboethoxy-2-cyclohexenone via hydrolysis. The concentration of hydrochloric acid is0.06mol/L. When the temperature is20℃, the reaction time is11h.The target product trinexapac-ethyl was finally synthesized through acylation and rearrangement reaction according to the references. The effects of acylating reagent dosage cyclopropyl chloride and reaction time on the acylation was studied. When the catalysis met n(DMAP):n(substrate) is0.14:1, it required7h to finish. The intermediates and the target compound were analyzed by MS and1HNMR. The improved method included the followed advantages:mild reaction condition, simple and safe operation.