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
S-acetals, which evolves as a tandem radical-polar process, is described. The reaction, which is carried out in the presence of a Cu(I) complex catalyst (10 mol%) and an inorganic base (i.e., carbonate), can be exploited as the key step for a novel, short, and versatile synthesis of the 3,4-disubstituted maleic anhydride nucleus.