Chemically triggered C–ON bond homolysis in alkoxyamines: regioselectivity and chemoselectivity
作者:Gérard Audran、Paul Brémond、Matisse Bim Batsiandzy Ibanou、Sylvain R. A. Marque、Valérie Roubaud、Didier Siri
DOI:10.1039/c3ob41549j
日期:——
Recently, we examplified the activation of the CâON bond homolysis by protonation, alkylation, benzylation, acylation, oxidation and complexation with a Lewis acid of the nitrogen atom of the 1-(pyridin-4-yl)ethyl fragment (Chem. Commun., 2011, 4291 and Org. Lett., 2012, 358) and of the 1-(pyridin-2-yl)ethyl fragment (J. Org. Chem. ASAP Doi:10.1021/jo401674v) of (N-(2-methylpropyl)-N-(1-diethylphosphono-2,2-dimethylpropyl)-N-oxyl) SG1-based alkoxyamines. The quaternization of the 1-(pyridin-3-yl)ethyl fragment by the aforementioned reactions was investigated for the corresponding SG1-based alkoxyamines. In sharp contrast to the quaternization at ortho and para positions of the pyridyl moiety, the effect of the quaternization at the meta position was weak. The effects of quaternization at ortho, meta and para positions were investigated through natural bond orbital and Mulliken charges, HOMOâLUMO interactions in the starting materials and the radical stabilization energy of the released 1-puridylmethyl radicals using DFT calculations with the B3LYP/6-31G(d) and UBMK/6-311+G(3df,2p)//R(O)B3LYP/6-31G(d) methods, respectively.
最近,我们通过质子化、烷基化、苄基化、酰基化、氧化以及与路易斯酸的配位,示例化了1-(吡啶-4-基)乙基片段(N-(2-甲基丙基)-N-(1-二乙基磷酸基-2,2-二甲基丙基)-N-氧基)SG1基醇氧胺中C–ON键的同裂键激活(化学通讯,2011,4291和有机快报,2012,358)以及1-(吡啶-2-基)乙基片段(J. Org. Chem. ASAP Doi:10.1021/jo401674v)。对于相应的SG1基醇氧胺,研究了通过上述反应对1-(吡啶-3-基)乙基片段的季铵化。与吡啶基部分的邻位和对位的季铵化形成相比,间位的季铵化效应较弱。通过自然键轨道和穆利肯电荷、起始材料中的HOMO-LUMO相互作用,以及利用DFT计算(B3LYP/6-31G(d)和UBMK/6-311+G(3df,2p)//R(O)B3LYP/6-31G(d)方法)释放的1-吡啶基甲基自由基的自由基稳定能,研究了季铵化在邻、间和对位的效应。