手性季碳立体中心的构建一直是有机化学中长期存在的挑战。特别是在生物化学中具有高度重要性的α-季氨基酸仍然缺乏直接的合成方法。我们在这里报道了一种加氢甲酰化方法来获得手性四元立体中心,这一直是过渡金属催化中的一个长期挑战。在温和条件下,α,β-不饱和羧酸衍生物在铑催化剂的作用下发生加氢甲酰化,生成 α-季立体中心。采用该方法可以合成多种手性α-季氨基酸,且对映选择性良好。深入研究表明,区域选择性受到与目标 C 连接的取代基的电子特性的显着影响C键。通过NMR和DFT分析,描绘了铑/Yanphos配合物的手性环境,并在此基础上提出了底物-催化剂相互作用模型。
Asymmetric hydroformylation of N-acyl 1-aminoacrylic acid derivatives by rhodium/chiral diphosphine catalysts
摘要:
The asymmetric hydroformylation of N-acylaminoacrylic acid esters 1 is efficiently catalysed by HRh(CO)(PPh3)3 in the presence of DIOP and related diphosphines as chiral ligands. The reaction is completely regioselective and affords in high yield the more branched aldehyde with the formyl group linked to a quaternary stereocenter. Irrespective of the structure of 1, preferential insertion of carbon monoxide always occurs onto the Re face of the substrate giving the (R)-antipodes in up to 60% enantioselectivity. Due to self enrichment during crystallisation, aldehyde 2b is readily isolated in 70-75% e.e.