肉香型香料4-甲基-5-噻唑乙醇的合成

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。44g氯气在30~35℃时于3~4h内通入到含有71g2-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81g,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50g,接着与60g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58g,用w(H2O2)=30%的过氧化氢130g氧化,萃取、蒸馏得到4-甲基-5-噻唑乙醇40·3g,质量分数98·8%,总收率50·2%。该合成工艺已经在50t/a的生产装置上中试放大,总收率为46·7%。

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

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%.