Cobaltocene-Induced Low-Temperature Radical Coupling Reactions in a Cobalt–Alkyne Series
Cobaltocene-Induced Low-Temperature Radical Coupling Reactions in a Cobalt–Alkyne Series
复制标题
钴-炔系列中二茂钴诱导的低温自由基偶联反应
DOI：
--
复制
发表时间：
2012
期刊：
影响因子：
--
通讯作者：
Ruth Sepanian
中科院分区：
文献类型：
--
作者：
G. Melikyan;B. Rivas;S. Harutyunyan;Louis Carlson;Ruth Sepanian
提出了一种低温生成CO_2(CO)_6-丙炔基的新方法。它包括原位制备各个阳离子物种(−50到−10°C)，并在−50°C下用钴Cp2Co快速还原它们。优化的实验方案适用于分子间和分子内反应，得到了拓扑上不同的α-芳基和α-napthyl，d，L-和Meso-1，5-己二炔和1，5-环十二炔。在分子间自由基C-C成键反应中，d，L构型是最好的空间排列(d，L 69-92%)，而在分子内环化反应中观察到立体选择性的逆转(介观79%)。在氧化条件下(Ce4+)，拆分得到L-3，4-二芳基-和d，L-3，4-(1-/2-萘基)-1，5-己二炔，产率为47-98%。通过引入外周酸敏官能团，如苄氧基和亚甲二氧基，并进行五步转化，显示了增强的功能耐受性。
A novel method for the low-temperature generation of Co2(CO)6-complexed propargyl radicals is developed. It consists of an in situ preparation of the respective cationic species (−50 to −10 °C) and their rapid reduction with cobaltocene, Cp2Co, at −50 °C. The optimized experimental protocol is applied to both inter- and intramolecular reactions, affording topologically diverse α-aryl and α-napthyl, d,l- and meso-1,5-hexadiynes and 1,5-cyclodecadiynes. The d,l configuration is the most preferable steric arrangement in intermolecular radical C–C bond-forming reactions (d,l 69–92%), while a reversal of stereoselectivity is observed in intramolecular cyclizations (meso 79%). Under oxidizing conditions (Ce4+), decomplexation affords d,l-3,4-diaryl- and d,l-3,4-(1-/2-naphthyl)-1,5-hexadiynes in good to excellent yields (47–98%). An enhanced functional tolerance is showcased by introducing peripheral acid-sensitive functionalities, such as benzyloxy and methylenedioxy groups, and carrying out a five-step convers...