肉香型香料4-甲基-5-噻唑乙醇的合成

Synthesis of Meat Flavor Perfume 4-Methyl-5-thiazoleethanol

以2-乙酰-γ-丁内酯和二硫代氨基甲酸铵为主要原料,通过氯化、脱羧、环合和氧化反应合成了4-甲基-5-噻唑乙醇.44 g氯气在30～35 ℃时于3～4 h内通入到含有71 g 2-乙酰-γ-丁内酯的碳酸氢钠水溶液,得到3-氯-2-乙酰-γ-丁内酯81 g,将它溶于w(HCl)=1%盐酸水溶液中,加热脱羧生成3-氯-5-羟基戊酮50 g,接着与60 g的二硫代氨基甲酸铵在40 ℃和pH=2的水溶液中反应,生成2-巯基-4-甲基-5-噻唑乙醇58 g,用w(H2O2)=30%的过氧化氢130 g氧化,萃取、蒸馏得到4-甲基-5-噻唑乙醇40.3 g,质量分数98.8%,总收率50.2%.该合成工艺已经在50 t/a的生产装置上中试放大,总收率为46.7%.

4-Methyl-5-thiazoleethanol was synthesized from 2-acetyl-γ-butyrolactone and ammonium dithiocarbamate through chlorination,decarboxylation,cyclization and oxidation.Thus,44 g chlorine gas was introduced into the mixture of 71 g 2-acetyl-γ-butyrolactone and aqueous NaHCO_3 solution at 30～35 ℃ for 3～4 h to yield 81 g 3-chloro-2-acetyl-γ-butyrolactone,which was heated at 100 ℃ in dilute hydrochloric acid solution to afford 50 g 3-chloro-5-hydroxy-2-pentanone(Ⅰ).Then Ⅰ reacted with 60 g ammonium dithiocarbamate and H_2O at 40 ℃ and pH=2 to give 58 g 2-mercapto-4-methyl-5-thiazoleethanol(Ⅱ).Finally Ⅱ was oxidized with 130 g 30% H_2O_2 to produce 40.3 g 4-methyl-5-thiazoleethanol in 50.2% overall yield and of 98.8% purity.Scale-up of this process in the scale of 50 t/a was carried out with total yield of 46.7%.