一种吡嗪酯类香料前体的制备及其热性能

为开发吡嗪酯类香料前体，以2,5-二甲基吡嗪氮氧和丙烯酸噻吩甲酯为原料，在醋酸钯的催化下经偶联反应，合成3-(3,6-二甲基-吡嗪氮氧-2-基)丙烯酸噻吩甲酯目标化合物，通过1H NMR、13C NMR、IR、HRMS表征其结构，并采用热重-微分热重（TG-DTG）和热裂解-气相色谱/质谱法（Py-GC/MS）测其热性能。结果表明：目标化合物从170 oC开始降解，主要热失重区间为170 oC~875 oC，在257 oC失重速率最大，总失重为76.5%。在300 oC~900 oC的有氧和无氧裂解氛围下，共鉴定出11种挥发性产物，主要有烷基吡嗪类、2-甲基噻吩、2-噻吩甲醇等特征香味物质，有氧氛围下热裂解产物种类较多，相对含量较高。依据主要裂解产物的种类及相对含量的变化，初步揭示了裂解机理。目标化合物在单料烟中的最适宜添加量为2 mg/kg。

Preparation and thermal property of the flavor precursor of pyrazine ester

In order to develop the flavor precursor of pyrazine ester, 2,5-dimethylpyrazine N-oxide and thiophene methyl acrylate were used as raw materials, and the target compound thiophen-2-ylmethyl-3-(3,6-dimethylpyrazine-2-yl)acrylate N-oxide was synthesized by coupling reaction with the catalysis of palladium acetate. The target compound was characterized by 1H NMR, 13C NMR, IR, HRMS, and its thermal property was measured by thermogravimetric-differential thermogravimetry (TG-DTG) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The results show that degradation temperature of the target compound is at 170 oC, and the main thermal weight loss range is 170 oC-875 oC. The maximum weight loss rate is 257 oC, and the total weight loss is 76.5%. Under the conditions of inert and oxidative atmosphere at 300 oC-900 oC, 11 volatile products are identified, and the main characteristic aroma compounds are alkylpyrazines, 2-methylthiophene and 2-thiophene methanol. In the oxidative atmosphere, there are more types of pyrolysis products, and their relative contents are higher than in inert atmosphere. According to the types and relative contents of the main pyrolysis products, the possible pyrolysis mechanism of the target compound is revealed. The optimum addition amount of the target compound in cigarette is 2 mg/kg.