2,6-二甲基吡啶经氧化、酯化、Claisen酯缩合后制得新型化合物2-乙酯基-6-乙酰基吡啶(4),用其作为前驱体,与一系列小分子脂肪胺:甲胺、乙胺、乙二胺在微波条件下生成3个吡啶酰胺化合物5,6,7.通过元素分析,1HNMR,IR和MS对这些化合物进行了表征.对6-乙酰基-N-甲基吡啶-2-甲酰胺(5)的X射线晶体衍射研究表明:其属于正交晶系,Pca2(1)空间群,晶胞参数a=2.2784(2)nm,b=0.4350(4)nm,c=0.9267(3)nm;α=β=γ=90°:Dc=1.288Mg·m^-3,V=0.91856(14)nm^3.实验还发现:2-乙酯基-6-乙酰基吡啶与脂肪胺及芳香胺缩合时会发生两类不同的反应,小分子脂肪胺选择与酯基发生胺解反应,而芳香胺则率先在乙酰基上发生席夫碱缩合.对这两类有趣的反应机理进行了深入探讨.
A new unsymmetric compound 2-carbethoxy-6-acetylpyridine (4) was synthesized from the starting material 2,6-dimethylpyridine through four reaction steps, and then a series of 6-acetylpyridine-2-carboxamides 5-7 were prepared by the microwave irradiation from the precursor 4. These compounds have been determined by the elemental analysis, 1H NMR, IR and MS spectra. The single crystal X-ray study of 6-acetyl-N-methylpyridine-2-carboxamide (5) indicates that 5 belongs to orthorhombic system, Pca2(1) space group, with a=2.2784(2) nm, b=0.4350(4) nm, c=0.9267(3) nm, α=β=γ=90°; Dc= 1.288 Mg·m^-3, V=0.91856(14) nm^3. The experiments suggest that different types of organic amines can result in different types of reactions and products when they react with the same precursor 2-carbethoxy-6-acetylpyridine under the same conditions, i.e., aliphatic amine affords amidation while aromatic amine leads to Schiff-base condensation.