Study on the Procees for the Preparation of Prohexadione and Its Analogs
|Keywords||prohexadione calcium plant growth regulator GC-MS rearrangement catalyst|
Prohexadione calcium(PDC) is a plant growth regulator(PGR), which inhibits the biosynthesis of gibberellin A (GA) in many plants to shorten their stems length. It is efficient in lodging resistance and mainly used in rice and grass. After fertilized by PDC, rice and grass is inhibited to synthesize GA1 so that their stalk growth can be controlled. At the same time, PDC is also able to promote the growth of rice grain and grass breeding. PDC can replace widely applied triazole inhibitors because of its smaller dosage, lower toxicity, less residue and non environmental pollution compared to triazole growth inhibitors. The literature reported process for PDC preparation and the current sythesis route is high-cost, low-yeild which is necessary to be adjusted to meet the needs of industrial production.On the basis of relevant references about synthesis of 2-acyl-1,3-hexadiones and PDC, Diethyl maleate was choosed as the staring material. After undergoing Michael addition, Claisen condensation, acylation, rearrangement, hydrolysis and salt formation, the target compound was obtained. The key factors of each step in the process like catalyst, temperature, time and so on were found and studied.In order to obtain the optimal experimental conditions, different conditions were designed and investigated. GC-MS was used to study the results of the experiments. After the optimization, yields and purity of the products were improved while waste and energy consumption was cut as for Claisen condensation, acylation and rearrangement steps. Reaction time of Michael addition and hydrolysis was obviously shortened. The whole yield of the process is increased up to 44%, laying a foundation for PDC’s industrial production. Besides, four PDC’s analogs have been prepared and biological activity tests will be committed later.