XY–ZH Systems as potential 1,3-dipoles. Part 8. Pyrrolidines and Δ<sup>5</sup>-pyrrolines (3,7-diazabicyclo[3.3.0]octenes) from the reaction of imines of α-amino acids and their esters with cyclic dipolarophiles. Mechanism of racemisation of α-amino acids and their esters in the presence of aldehydes
作者:Kitti Amornraksa、Ronald Grigg、H. Q. Nimal Gunaratne、James Kemp、Visuvanathar Sridharan
DOI:10.1039/p19870002285
日期:——
Imines of α-amino acid esters with aromatic, heterocyclic, and aliphatic aldehydes generate azomethine ylides stereospecifically by a prototropic shift on heating in toluene. The azomethine ylides undergo cycloaddition to N-phenylmaleimide, maleic anhydride, and p-naphthoquinone via an endo-transition state to give racemic, single diastereoisomeric, cycloadducts. α-Amino acids undergo analogous cycloadditions
α-氨基酸酯的亚胺与芳族,杂环和脂族醛一起,通过在甲苯中加热时发生质变,立体定向生成偶氮甲碱。甲亚胺叶立德进行环加成到Ñ苯基马来,马来酸酐,和p -naphthoquinone经由一个内切-过渡状态,得到外消旋的,非对映异构单,cycloadducts。α-氨基酸在热乙酸中经历类似的环加成而不脱羧。讨论了在醛存在下α-氨基酸及其酯的外消旋作用机理。吡咯烷cycloadducts(22)平滑地氧化成相应的Δ 5 -pyrrolines(33)通过二氯二氰基对苯醌。