Studying competitive lithiations at alpha-, ortho-, and benzylic positions in various N-protected aniline derivatives
作者:Martin Schmid、Birgit Waldner、Michael Schnürch、Marko D. Mihovilovic、Peter Stanetty
DOI:10.1016/j.tet.2011.02.056
日期:2011.4
The directing effects of the t-BuOCONH– (NHBoc) and the t-BuCONH– (NH–pivaloyl) groups have been investigated on a series of differently substituted anilines. Depending on the nature of the directing group and the substrate, lithiation either occurred in the ortho-, benzylic-, or alpha-position. In general, it was observed that ortho-lithiation is the least facile process and alpha-lithiation slightly
所述的定位效应吨-BuOCONH-(NHBoc基)和吨-BuCONH-(NH新戊酰)基团已被研究了一系列不同取代的苯胺。取决于定向基团和底物的性质,锂化要么发生在邻位-,苄基或α-位。通常,观察到邻位锂化是最不容易的过程,与苄基位置的锂化相比,α-锂化略受青睐。然而,发现起始材料的微小变化导致在金属化过程中不同的区域选择性。例如,将取代基从甲基改变为乙基可导致完全不同的区域选择性。作为最后的结论,提出了锂化实验的图形指南。