Reductive cyclization of carbon-centered glycine radicals; a novel synthetic route to cyclic α-amino acids
作者:Peter M. Esch、Henk Hiemstra、Richard F. de Boer、W.Nico Speckamp
DOI:10.1016/s0040-4020(01)81240-0
日期:1992.1
Reductive cyclizations (tributylin hydride, AIBN) of several α-(penthylthio)glycine derivatives with a 30alkenyl substituent at nitrogen are reported. These reactions proceed via 2-aza-5-alken-1-yl radicals as intermediates which bear electron-withdrawing carbonyl substituents at the radical center and at nitrogen. Such radicals can be considered as relatively stable captodative radicals, but are reactive
报道了几种在氮上具有30个烯基取代基的α-(苯硫基)甘氨酸衍生物的还原环化作用(氢化三丁基氢化物,AIBN)。这些反应通过2-氮杂-5-烯-1-基作为中间体进行,该中间体在自由基中心和氮上带有吸电子羰基取代基。这样的基团可以被认为是相对稳定的Capdudative基团,但是对于烯烃环化而言是足够反应性的。主要产物通常来自5- exo环化,是脯氨酸在结构上令人关注的类似物。经由6-哌啶酸类似物的不同量的内切在某些情况下,也可以得到环化。乙炔的类似环化是成功的,而腈则不能环化。