A General Approach to Substituted Benzimidazoles and Benzoxazoles
<i>via</i>
Heterogeneous Palladium‐Catalyzed Hydrogen‐Transfer with Primary Amines
作者:Marianna Pizzetti、Elisa De Luca、Elena Petricci、Andrea Porcheddu、Maurizio Taddei
DOI:10.1002/adsc.201200253
日期:2012.9.17
employed. Primary amines are the most suitable reagents for the atom economy of the overall process that resulted to be general as several different substituted benzimidazoles were obtained in good yield. Benzoxazoles can be also prepared starting from primary amines and o‐aminophenol. The reaction is also highly selective as no (poly)‐alkylated phenylenediamines or cross‐contaminated benzimidazoles are
据报道,在钯/炭存在下,以邻苯二胺和胺为原料合成苯并咪唑。在微波电介质加热,可以使用叔胺,仲,和甚至伯胺作为底物为钯-介导的过程中得到的2-取代的或1,2-二取代的苯并咪唑,取决于性质ø -使用的苯二胺。对于整个过程的原子经济性而言,伯胺是最合适的试剂,由于获得了数种不同的取代苯并咪唑类,它们的收率很高,因此普遍使用。苯并恶唑也可以从伯胺和邻氨基苯甲酸开始制备氨基苯酚 由于没有从(N-单烷基苯二胺)获得(多)烷基化的苯二胺或交叉污染的苯并咪唑,该反应的选择性也很高。这种行为被解释为与N-烷基芳基胺的芳族NH键连接的亚甲基脱氢的稀缺性。实验进行了同意,以画出过程中发生的反应路径的几乎完整图景。催化剂可以循环使用几次,尽管远未达到最佳性能,但催化剂TON = 90对于进一步的大规模优化方案是令人鼓舞的。此外,上的木炭催化微波辅助反应在钯Ò苯二胺使叔胺脱烷基并转化为仲胺。