Aggregative activation in heterocyclic chemistry. Part 4. Metallation of 2-methoxypyridine: unusual behaviour of the new unimetal superbase BuLi–Me2N(CH2)2OLi (BuLi–LiDMAE)
作者:Philippe Gros、Yves Fort、Paul Caubère
DOI:10.1039/a701914i
日期:——
A series of potential unimetal superbases BuLiâROLi has been studied in order to increase the basicity/nucleophilicity ratio ([B/N]R) of BuLi. The best [B/N]R ratio is found with BuLiâLiDMAE. This complex base apparently metallates 2-methoxypyridine at the unexpected C-6 position. It is shown that no actual metallated species are formed in the reaction medium, the reaction occurring as the result of a common radical precursor stabilized by an aggregate cluster. Finally, as an application, C-6 substituted 2-methoxypyridines have been obtained in good to excellent yields.
为了提高BuLi的基本性/亲核性比率([B/N]R),研究了一系列潜在的单金属超碱BuLi–ROLi。最佳的[B/N]R比率是在BuLi–LiDMAE中发现的。这种复合碱显然在意想不到的C-6位点对2-甲氧基吡啶进行了金属化。研究表明,在反应介质中并没有形成实际的金属化物种,该反应是由于一个通过聚集簇稳定的共同自由基前体的结果。最后,作为应用,得到了C-6取代的2-甲氧基吡啶,产率良好到优异。