Zhao Xiaodan, Glover Garrett S, Oberg Kevin M, Dalton Derek M, Rovis Tomislav
Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA.
Synlett. 2013 Jun 17;24(10). doi: 10.1055/s-0033-1338842.
Pentafluorophenyl triazolium carbenes, widely used in NHC-catalysis, can decompose by several mechanisms. Under high concentration conditions, the azolium may undergo a pentafluorophenyl exchange by a proposed SAr mechanism to give an inactive salt. In the presence of appropriate substrates, cyclization on the -position of the arene can occur, also by SAr. These adducts provide a potential pathway for catalyst decomposition and serve as a caveat to the development of new reactions and catalysts.
广泛应用于氮杂环卡宾催化的五氟苯基三唑鎓卡宾可通过多种机制分解。在高浓度条件下，唑鎓可能通过一种假定的亲核芳香取代（SAr）机制发生五氟苯基交换，生成一种无活性的盐。在合适的底物存在下，也可通过亲核芳香取代在芳烃的α位发生环化反应。这些加合物为催化剂分解提供了一条潜在途径，也为新反应和催化剂的开发敲响了警钟。
