将1,3-丁二烯二羰基化为己二酸衍生物可为更具成本效益和环境友好的工业生产提供潜力。然而,区域异构体羰基化和异构化途径的复杂反应网络使得选择性和直接转化特别困难。在这里,我们报道了在存在1,2-双-二叔丁基膦膦-二甲苯(d t bpx)配体的情况下,钯催化的这一过程产生了令人惊讶的溶剂影响,这些配体允许由1,3-丁二烯,碳形成己二酸酯二酯。一氧化碳和甲醇,在可扩展条件下具有97%的选择性和100%的原子经济性。在最佳条件下,可以以高至极好的收率获得各种1,2-和1,3-二烯的二酯和三酯。
Ruthenium-catalyzed formal [4 + 2] cycloaddition of alkynes with alkenes: formation of cyclohexenedicarboxylates via isomerization of alkynes and successive Diels–Alder reaction
Abstract Formal [4 + 2] cycloaddition of alkynes with electron-deficient alkenes, which affords 3,6-dialkyl-4-cyclohexene-1,2-dicarboxylates, was achieved using Ru(η 6 -1,3,5-cyclooctatriene)(η 2 -dimethyl fumarate) 2 as a catalyst. The reaction mechanism consists of two steps, isomerization of an alkyne to conjugated dienes and successive Diels–Alder reaction of the generated dienes with an electron-deficient
To rich flavor additive species of pyrazines, two new compounds of 3,6-dimethyl-2,5-pyrazinedicarboxylic acid 1-octen-3-yl ester (DMPOE) and 3,5,6-trimethyl-2-pyrazinecarboxylic acid 1-octen-3-yl ester (TMPOE) were synthesized by KMnO4 oxidation, acylating chlorination and esterification reaction, in which tetramethylpyrazine and 1-octen-3-ol were used as initial materials. Thermogravimetry (TG), differential scanning calorimeter (DSC) and pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS) were conducted to investigate the thermal degradation behaviors of DMPOE and TMPOE. TG–DTG results indicated that the T p of DMPOE and TMPOE with the largest mass loss rate was at 310 and 250 °C, respectively. The T peak of DMPOE and TMPOE showed by DSC curves was 301.8 and 260.0 °C, respectively. Py–GC/MS was performed to benefit the simulation of cigarette burning conditions, and the results indicated that DMPOE and TMPOE could release specific flavors of 1-octen-3-ol and diversified alkylpyrazines. Furthermore, the thermal degradation mechanisms of the flavor precursors of DMPOE and TMPOE were discussed. The study on the thermal behavior of these two methylpyrazinecarboxylates would provide theoretical basis for their application in tobacco.