Selective N-Alkylation of Indoles with α,β-Unsaturated Compounds Catalyzed by a Monomeric Phosphate
作者:Hanako Sunaba、Keigo Kamata、Noritaka Mizuno
DOI:10.1002/cctc.201402309
日期:2014.8
Catalytic N‐alkylation of indoles is challenging because the N1 nitrogen atoms are inert toward electrophilic reagents. Herein, an organic‐solvent‐soluble alkylammonium salt of a simple monomeric phosphate ion, [PO4]3−, with a high charge density acts as an efficient homogeneous catalyst for selective N‐alkylation of indoles with α,β‐unsaturated compounds. For the reaction of indole with ethyl acrylate
吲哚的催化N-烷基化具有挑战性,因为N1氮原子对亲电试剂呈惰性。在此,具有高电荷密度的简单单体磷酸根离子[PO 4 ] 3−的有机溶剂可溶的烷基铵盐可作为有效的均相催化剂,用于用α,β-不饱和化合物对吲哚进行选择性N-烷基化。对于吲哚与丙烯酸乙酯的反应,周转数达到36,周转频率为216h -1。这些值是迄今为止针对基础介导系统报告的最高值。在[PO 4 ] 3-的存在下离子,氮亲核试剂的各种组合(十个实例)和α,β-不饱和化合物(四个实例)以高收率有效地转化为所需的N-烷基化产物。NMR和IR光谱表明,吲哚阴离子是通过[PO 4 ] 3--离子激活吲哚而形成的,这在当前的N-烷基化中起着重要作用。