Dearomatization and Functionalization of Terpyridine Ligands Leading to Unprecedented Zwitterionic Meisenheimer Aluminum Complexes and Their Use in Catalytic Hydroboration
作者:Guoqi Zhang、Jing Wu、Haisu Zeng、Michelle C. Neary、Matthew Devany、Shengping Zheng、Pavel A. Dub
DOI:10.1021/acscatal.8b04096
日期:2019.2.1
terpyridine (tpy) ligands via 2′/6′-, 3′/5′-, or 4′-selective alkylation of the central pyridine ring. The reaction is mediated by the most abundant metal in the Earth’s crust, aluminum (Al), and depending on the conditions employed, exhibits ionic or radical character as suggested by experimental and computational analysis. In the latter case, intermediate formation of an AlIII complex supported by π-radical
本文报道了通过中央吡啶环的2'/ 6'-,3'/ 5'-或4'-选择性烷基化使遍在的吡啶(tpy)配体脱芳香化的第一个例子。该反应是由地壳中最丰富的金属铝(Al)介导的,并且根据所采用的条件,它表现出离子或自由基的特性,这是实验和计算分析所表明的。在后一种情况下,由π自由基单阴离子配体(tpy •)1–支撑的Al III络合物的中间形成是显而易见的。3'/ 5'-烷基化导致空前的两性离子迈森海默Al III配合物,被确定为选择性氢硼化C═O和C functionalC官能团的有效前催化剂。高达〜1000的周转数(TONs)使相应的络合物进入迄今为止报道的标题反应最有效的Al催化剂类别。获得的数据表明,一氢化铝或更可能是二氢化铝可能是相关的催化物质。或者,也可以想象一种机械化的情况,其中脱芳族化的“化学上无害的”配体充当氢化物供体,并且将来有必要对此进行详细研究。