Correlations between carbon-13 nuclear magnetic resonance chemical shifts and reactivities of siloxybutadienes and siloxyazabutadienes in the Diels-Alder reaction with dimethyl acetylenedicarboxylate.
In the reaction of silylated butadiene derivatives (1) with dimethyl acetylenedicarboxylate (DMAD), it is proposed that the reactivities of the dienes can be predicted from the carbon-13 nuclear magnetic resonance chemical shifts of the terminal methylene carbons (δ13C-4) of the dienes based on the following linear relationships, a) total electron densities against δ13C-4; b) ln k against 1/[ELUMO(DMAD)-EHOMO(diene)]; c) ln k against δ13C-4. The total electron densities and energy levels of highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs) of the dienes were calculated by the modified neglect of diatomic overlap (MNDO) method.
在硅烷化丁二烯衍生物 (1) 与乙炔二甲酸二甲酯(DMAD)的反应中,建议根据二烯末端亚甲基碳(δ13C-4)的碳-13 核磁共振化学位移,按照以下线性关系预测二烯的反应活性:a) 总电子密度与δ13C-4 的关系;b) ln k 对 1/[ELUMO(DMAD)-EHOMO(二烯)]; c) ln k 对 δ13C-4。二烯的总电子密度以及最高占位分子轨道(HOMOs)和最低未占位分子轨道(LUMOs)的能级是通过修正的忽略二原子重叠(MNDO)法计算得出的。
Synthesis of highly-functionalised pyridines via hetero-Diels–Alder methodology: reaction of 3-siloxy-1-aza-1,3-butadienes with electron deficient acetylenes
作者:Matthew D. Fletcher、Timothy E. Hurst、Timothy J. Miles、Christopher J. Moody
DOI:10.1016/j.tet.2006.03.051
日期:2006.6
The hetero-Diels-Alder reaction between 1-aza-3-siloxy-1,3-butadienes and electron deficient acetylenes is described. The reactivity of a range of alpha,beta-unsaturated oximes and hydrazones is assessed in the synthesis of tri- and tetra-substituted pyridines bearing an oxygen functionality at C-3. Microwave irradiation has been employed to decrease the extended reaction times and increase the poor yields often associated with this reaction. (c) 2006 Elsevier Ltd. All rights reserved.
Pyridine Syntheses. IV. The Preparation of Some Vitamin B<sub>6</sub> Analogs