Study On The Synthesis And Flavor Characteristic Of 3-Alkoxythiophene And 3-Thienyl Sulfide

The sulfur-containing meat flavor compounds are popular with its strong meaty, low threshold, distinctive characteristic in fragrance domain. The fragrance features of 3-substituted thiophene are less reported. In order to seek and utilize the sulfur-containing meat flavor compounds further, we designed and synthesized nine 3-alkoxythiophene and nine 3-thienyl sulfide which had similar structure. All these compounds were confirmed by IR, MS and ¹HNMR spectrographic analysis and their fragrance features were evaluated, which showed that they all had meat flavor.Thiophene reacted with bromine and zinc to obtain 3-bromothiophene via substitution and reduction reaction. 3-Methoxythiophene was synthesized from 3-bromothiophene and surplus sodium methoxide with cuprious bromide as catalyst, NMP. Then 3-pentoxythiophene was synthesized from 3-methoxythiophene and n-pentanol with anhydrous sodium bisulfate as catalyst. The effects of molar ratio, amount of catalyst, reaction time and reaction tempreture on the yield of 3-pentoxythiophene via orthogonal experiment were investigated. The optimum reation conditions were confirmed. According to the modified optimal reaction conditions, other eight 3-alkylthiophenes were synthesized from 3-methoxythiophene and the corresponding alcohol with sodium bisulfate as catalyst. In addition, 3-bromothiophene was treated with n-butyllithium under -70? and followed with sulfur, halid in anhydrous tetrahydrofuran and n-hexane to give II₁ II₆, which all had high yields and purity. Also, 3-iodothiophene was treated with active magnesium powder under room temperature and followed with diethers in anhydrous hexane to gave II₇ II₉.The fragrance features were identified, which showed that they all had meat flavor. The series of I compounds were had strong onion, garlic, roasted meaty, cooked meaty and the series of II compounds were had intense caramel, onion, garlic, roasted meaty, cooked meaty. Results of flavor threshold showed that the series of I and II compounds all had intense meaty and low threshold. The fragrance holding time distribution of the series of I compounds is wider than that of series of II compounds and the seriesof I compounds can be used as top note, body note, basic note while the series of compounds II can be used as top note, body note in imitation flavor.