Synthesis Of Pyrazine Aroma Derivatives And Their Application In Cigarette Flavoring

In recent years,the strategy of direct functionalization has become a powerful tool for the rapid assembly of alkenyl,alkyl,and ester pyrazines in the field of organic synthesis chemistry because of its unique advantages in atomic economy and step economy.Moreover,pyrazine compounds are widely used in medicine,agriculture,functional materials,food,daily chemicals,and other fields.From the point of view of the development of sustainable and environment-friendly chemistry,it is of great research value to further develop novel and green synthesis methods.In this paper,the new synthesis strategies of coupling pyrazine derivatives with alcohols and benzoyl acetonitriles via the C-H bond and the C-CN bond were studied,and a series of alkene and alkyl pyrazine compounds and pyrazine esters were constructed.The aroma characteristics and aroma intensity of each series of target compounds were discussed by aroma evaluation.At the same time,this paper also studied the thermogravimetric analysis,pyrolysis analysis,and cigarette flavor effect of some representative flavor compounds.The research results provide a new research direction for the preparation and application of pyrazine monomers and are expected to provide some theoretical support for basic research and practical application in the fields of cigarette spices and hot-processed products.1.Synthesis,aroma evaluation,thermal behavior analysis,and cigarette flavor effect of alkene-and alkyl-substituted pyrazines:(1)In this study,dehydrogenation coupling reactions facilitated by the t-Bu OK/18-crown-6 catalytic system were used to synthesis10 alkenylpyrazines and 11 alkylpyrazines.The approach was more environmentally friendly and efficient,and it could selectively manufacture different target compounds by regulating the reaction temperature.It also had a greater step economy.(2)The alkylation target products have a loam scent in general,and a burn aroma in general,and the aroma strength drops gradually and fades as the number of carbon atoms in the compound increases.(3)Compounds 3e,3i,4g,and 4j exhibited good room temperature stability,volatilized entirely in the burning stage of cigarettes,and pyrolysis generated fragrance compounds with roasted,nutty,green,and floral scents.(4)The findings revealed that when the concentration of compound 3e was 3 mg/kg,it had a honey-sweet scent coordinated with tobacco aroma,and the aroma quality of cigarettes was considerably enhanced when the concentration of compound 4j was 7 mg/kg,which could improve the aroma quantity and richness of the smoke.2.Synthesis,aroma evaluation,thermal behavior analysis,and cigarette flavor effect of pyrazine esters:(1)In Ar atmosphere,the esterification method of C-CN bond functionalization catalyzed by Na2CO3/15-crown-5 system was developed,and 15 pyrazinyl esters were synthesized.The method has advantages of green environmental protection,mild conditions,strong tolerance of functional groups and good gram practicability.(2)The aroma of these series of compounds is often that of wood or green incense,and the strength of the perfume steadily decreases until tasteless as the number of carbon atoms in the substituent group increases.(3)In the simulated cigarette combustion process,compounds 7b,7f,and 7g were stable at room temperature,volatilized almost entirely,and created a tiny quantity of pyrolysis products with chocolate,baked,cocoa,and balsam scents.(4)Compound 7b has a suitable sweet fragrance when the concentration is 3 mg/kg,which can effectively reduce the irritation and dryness of smoke and improve sweetness,whereas compound 7f has a suitable cream popcorn aroma when the concentration is 1 mg/kg,which can significantly improve the aroma and delicate softness of smoke and have higher smoking comfort.