A variety of nonactivated hindered aromatic rings are acyloxylated (22 examples, up to 83% yield) in the presence of PPh3AuCl as the catalyst and di(acetoxy)iodobenzene as the oxidant. The reaction proceeds at 110 degrees C in an acid media and allows the formation of both hindered acetoxy and acyloxy derivatives. This methodology nicely complements the Pd-catalyzed arene acyloxylation reaction, which is not operating on hindered substrates and allows the Au-catalyzed unprecedented acyloxylation reaction of arenes, implying various carboxylic acids.
Bulky diarylammonium arenesulfonates as mild and extremely active dehydrative ester condensation catalysts
作者:Akira Sakakura、Shoko Nakagawa、Kazuaki Ishihara
DOI:10.1016/j.tet.2005.09.059
日期:2006.1
especially large-scale, fundamental reactions like estercondensations, are highly desirable for many reactions. Bulky diarylammonium pentafluorobenzenesulfonates and tosylates serve as extremely active dehydration catalysts for the estercondensation reaction of carboxylicacids with equimolaramounts of sterically demanding alcohols and acid-sensitive alcohols. Typically, the esterification reaction is performed