Catalyst-free photoredox addition-cyclisations: exploitation of natural synergy between aryl acetic acids and maleimide.
Catalyst-free photoredox addition-cyclisations: exploitation of natural synergy between aryl acetic acids and maleimide.
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DOI：
10.1002/chem.201304929
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发表时间：
2014-04-25
期刊：
影响因子：
--
通讯作者：
Walton JC
中科院分区：
文献类型：
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作者：
Manley DW;Mills A;O'Rourke C;Slawin AM;Walton JC
当在马来酰亚胺存在下用UVA照射时，适当官能化的羧酸经历先前未知的光氧化还原反应。发现马来酰亚胺协同地充当自由基生成光氧化剂和自由基受体，否定了对外在光氧化还原催化剂的需要。在13个制备性光解反应中，获得了中等至优异的产物色满吡咯二酮、硫代色满吡咯二酮和吡咯喹啉二酮衍生物的产率。原位NMR光谱用于研究每个反应。监测反应物衰减和产物积累，从而能够绘制反应曲线。一个合理的机制，即光激发的马来酰亚胺作为氧化剂产生自由基离子对，已被假定，并支持UV/维斯。光谱学和DFT计算。的自由基阳离子反应中间体，其特征在于在溶液中通过EPR光谱。
Suitably functionalised carboxylic acids undergo a previously unknown photoredox reaction when irradiated with UVA in the presence of maleimide. Maleimide was found to synergistically act as a radical generating photoxidant and as a radical acceptor, negating the need for an extrinsic photoredox catalyst. Modest to excellent yields of the product chromenopyrroledione, thiochromenopyrroledione and pyrroloquinolinedione derivatives were obtained in thirteen preparative photolyses. In situ NMR spectroscopy was used to study each reaction. Reactant decay and product build-up were monitored, enabling reaction profiles to be plotted. A plausible mechanism, whereby photo-excited maleimide acts as an oxidant to generate a radical ion pair, has been postulated and is supported by UV/Vis. spectroscopy and DFT computations. The radical-cation reactive intermediates were also characterised in solution by EPR spectroscopy.