Studies on the origin of cis-diastereoselectivity of the titanium-mediated cyclopropanation of carboxylic esters with Grignard reagents. Stereochemistry of the intramolecular cyclization of β-metalloketones
作者:Dzmitry G. Kananovich、Oleg G. Kulinkovich
DOI:10.1016/j.tet.2007.10.075
日期:2008.2
Datа on the stereochemistry of the intramolecular cyclization of β-metaloketones into 1,2-disubstituted cyclopropanols are in agreement with the cyclopropanation of carboxylic esters with alkoxytitanacyclopropane reagents proceeding via the β-titanoketone intermediates with the metal atom bound to a secondary carbon. Hypothesis for the origin of cis-diastereoselectivity of the cyclization of the β-titanoketones
关于将β-金属酮分子内环化为1,2-二取代的环丙醇的立体化学数据,与羧酸酯与烷氧基钛烷环丙烷试剂的环丙烷化反应是一致的,该反应是通过β-钛酮中间产物进行的,其中金属原子与仲碳相连。提出了关于β-钛酮环化的顺式-非对映选择性起源的假说。它解释了通过减轻八面体钛原子上的配体之间的排斥应变而优选形成顺式-1,2-二取代的环丙醇的趋势。