2-酰胺-6-乙酰基吡啶类化合物的微波合成及其晶体结构

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, ¹H NMR, 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°; D_c＝1.288 Mg•m^－3, V＝0.91856(14) nm³. 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.

Microwave Irradiation Synthesis and the Crystal Structure of 6-Acetylpyridine-2-carboxamides

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 or-thorhombic 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°; D_c＝1.288 Mg•m^－3, V＝0.91856(14) nm³. 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.