The Study On The Total Synthetic Technology Of Spices Karanal

Karanal is an advanced acetal spices with a strong amber aroma, which is mainlyused in daily essence. To the best of our knowledge, there was no reports of Karanal’stotal synthesis to date, therefore, it has great significance to study the Karanal ’s totalsynthesis technique and achieve the industrialized production in the spices industry ofChina. In this study, spices Karanal was prepared by2-methyl diethyl malonate,2-bromobuta-ne and privet aldehyde through alkylation、restore and aldol condensationreactions. Technological parameters of these reactions were optimized through singlefactor method and responses surface analysis. The Intermediates2-methyl-2-sec-butyldiethyl malonate,2-methyl-2-sec-butyl1,3-propanediol and final product Karanalwere analyzed by1HNMR to identify the molecular structure.The researching contentsdescribed as follows：Intermediates2-methyl-2-sec-butyl diethyl malonate [Ⅰ] was prepared by2-methyl diethyl malonate and2-bromobutane through alkylation reaction. The optimumconditions under sodium alkoxide as the catalyzer were determined as follows: themolar ratio was n (2-methyl diethyl malonate): n(Na): n(2-Bromobutane)=1:2:2.2,the reation time was3.5hours and reaction temperature was about65℃. The yield of2-methyl-2-sec-butyl diethyl malonate at the optimal condition was71%.Intermediates2-methyl-2-sec-butyl-1,3-propanediol [Ⅱ] was prepared by2-methyl-2-sec-butyl diethyl malonate through reduction reaction with Na/C2H5OH asreducing agent. The optimum conditions were determined as follows: the molar ratiowas n(Na): n(2-methyl-2-sec-butyl diethyl malonate)=12:1, the reaction time was2hours and reaction temperature was about110℃. The yield of2-methyl-2-sec-butyl-1,3-propanediol at the optimal condition was78.9%.The final product Karanal was prepared by2-methyl-2-sec-butyl1,3-propanedioland privet aldehyde. The optimum conditions under potassium bisulfate as thecatalyzer were determined as follows: the suitable conditions optimized through sigle factor method with temperature at100℃，reaction time at90min, the catalystamounts were3g/mol, and n(privet aldehyde): n(2-methyl-2-sec-butyl1,3-propanediol)was1.2:1．The yield of Karanal at the optimal condition was73.3%.Based on the synthesis technology, this study designed a new methodology andthus achieved the total synthesis for Karanal’s essence. To the best of our knowledge,this is the first study on this topic. The current research on the synthesis ofintermediates [Ⅱ] and Karanal was mostly on mechanistic aspects of organic reaction.The application and industrial production remain as an ongoing challenge. The studyoriginally developed the total synthesis technique of Karanal’s products, which hasestablished a solid foundation for the industrial production of Karanal in China.