Various aromatic lactones have been synthesized and their regioselectivity (1,2-addition vs. 1,4- or 1,6-addition) investigated in reactions with organolithium species, particularly n-BuLi and sec-BuLi. The regioselectivity varied greatly depending on various factors, such as the bulkiness of both substrates and organolithium species, and types of solvent and cosolvent. In particular, 1,4-addition with dearomatization occurred preferentially using sec-BuLi as the nucleophile in tetrahydrofuran (THF) with hexamethylphosphoramide (HMPA) or N,N′-dimethylpropyleneurea (DMPU) as cosolvent. For sec-BuLi, the reaction was estimated to proceed through a single-electron transfer mechanism.
我们合成了各种芳香族内
酯,并研究了它们在与
有机锂(尤其是正-BuLi 和仲-BuLi)反应时的区域选择性(1,2-加成与 1,4- 或 1,6- 加成)。反应的区域选择性因各种因素(如底物和
有机锂的体积、溶剂和助溶剂的类型)的不同而有很大差异。特别是,在以六
甲基磷酰胺(HMPA)或 N,N′-二
甲基丙烯脲(
DMPU)为共溶剂的
四氢呋喃(THF)中,以仲丁
锂为亲核体的 1,4-加成
脱芳香化反应优先发生。对于
仲丁基锂,估计反应是通过单电子转移机制进行的。