CuCl-catalyzed radical cyclisation of N-α-perchloroacyl-ketene-N,S-acetals: a new way to prepare disubstituted maleic anhydrides
作者:Andrea Cornia、Fulvia Felluga、Vincenzo Frenna、Franco Ghelfi、Andrew F. Parsons、Mariella Pattarozzi、Fabrizio Roncaglia、Domenico Spinelli
DOI:10.1016/j.tet.2012.04.117
日期:2012.7
The copper-catalyzed radical cyclization (RC) of N-α-perchloroacyl cyclic ketene-N,X(X=O, NR, S)-acetals was studied. While the RC of N-acyl ketene-N,O-acetals was unsuccessful, the 5-endo cyclization of the other ketene acetals provided much better results, with the following order of cyclization efficiency: hexa-atomic cyclic ketene-N,NR-acetals
研究了N -α-全氯酰基环状烯酮-N,X(X = O,N R,S)-乙缩醛的铜催化自由基环化(RC)。同时的RC Ñ酰基二硫缩烯酮Ñ,ö -acetals不成功,5-内提供更好的结果的其它烯酮缩醛的环化,以环化效率顺序如下:六原子环二硫缩烯酮Ñ,Ñ ř -乙缩醛<五原子环烯酮-N,S-乙缩醛<六原子环烯酮-N,S-缩醛。催化循环总是从氨基甲酰基甲基自由基的形成开始。这导致反应级联,包括自由基极性交叉步骤,该步骤以马来酰亚胺核或其前体的形成结束。来自六原子环状烯酮-N,S-乙缩醛的RC的产物被有效地转化为二取代的马来酸酐。