Synthesis of Asymmetrically Substituted Terpyridines by Palladium‐Catalyzed Direct CH Arylation of Pyridine
<i>N</i>
‐Oxides
作者:Sasa Duric、Fanni D. Sypaseuth、Santina Hoof、Emma Svensson、C. Christoph Tzschucke
DOI:10.1002/chem.201302118
日期:2013.12.16
The synthesis of asymmetrically substituted 2,2′:6′,2′′‐terpyridines is reported. First, palladium‐catalyzed CH arylation of pyridine N‐oxides with substituted bromopyridines gave 2,2′‐bipyridine N‐oxides, which were further arylated in a second step to form 2,2′:6′,2′′‐terpyridine N‐oxides. Yields of up to 77 % were obtained with N‐oxides bearing an electron‐withdrawing ethoxycarbonyl substituent
报道了不对称取代的2,2':6',2''-叔吡啶的合成。首先,钯催化的C ^ ħ吡啶芳基化Ñ -oxides与取代的溴吡啶,得到2,2'-联吡啶Ñ -oxides,其中在第二步骤中进一步芳基化以形成2,2':6',2'' -特吡啶N-氧化物。使用在4位带有吸电子乙氧基羰基取代基的N氧化物,收率高达77%。带有P(t Bu)3或P(邻甲苯基)3的Pd(OAc)2被用作催化剂。衍生自Pd(OAc)2的环金属配合物这些膦也有效。以K 3 PO 4为碱比K 2 CO 3可获得更好的结果。随后用H 2和Pd / C作为催化剂进行脱氧,得到了接近定量收率的不对称取代的2,2':6',2''-吡啶。与已知的交叉偶联方法相比,该反应序列显着减少了所需的步骤数,因此可以方便且可扩展地使用取代的吡啶。