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。
Rhodium-Catalyzed Asymmetric Cyclodimerization of Oxabenzonorbornadienes and Azabenzonorbornadienes: Scope and Limitations
作者:Anna Allen、Paul Le Marquand、Ryan Burton、Karine Villeneuve、William Tam
DOI:10.1021/jo7012884
日期:2007.10.1
Cationic rhodium(I)-catalyzed cyclodimerization of oxabenzonorbornadienes produced naphtho[1,2-b]furan ring systems in a single step with excellent yields and excellent enantioselectivities. The effect of various Rh(I) catalysts, Ag(I) salts, solvents, and phosphine ligands on the yield and enantioselectivity of the reaction was investigated, and the scope and limitations of this reaction with various
阳离子铑(I)催化的氧杂苯并降冰片二烯环二聚反应可一步合成萘[1,2- b ]呋喃环系统,并具有优异的收率和出色的对映选择性。研究了各种Rh(I)催化剂,Ag(I)盐,溶剂和膦配体对反应收率和对映选择性的影响,并研究了该反应与各种恶双环烯的范围和局限性。用氮杂苯并降冰片二烯类似物获得了相似的结果,以优异的产率和优异的对映选择性提供了相应的环二聚产物。
1a-c underwent chemoselective oxa-di-pi-methane rearrangement under sensitized conditions and suffered formal ketene extrusion upon direct irradiation. Direct irradiation of 1d afforded 11d via formal ketene extrusion but under sensitization it remained unchanged. Oximes 2a-d suffered ketene extrusion upon direct irradiation and E/Z isomerization under sensitized conditions. On the other hand, 5-methylenebicyclo[2