Alkynes were oxidized efficiently using the catalytic amount of PdCl2 and CuCl2 in PEG-400 in the presence of water, providing excellent yields of the corresponding 1,2-diketones. A variety of alkynes were well-suited substrates for the oxidation under the described conditions. Further, the optimized conditions were successfully utilized for the one-potsynthesis of 2,3-disubstituted quinoxaline derivatives
ABSTRACT The synthesis of N-heterocycles of quinoxalines has been developed by an efficient protocol of one-pot annulation of alkynes with o-phenylenediamines. A variety of quinoxalines were prepared in good to high yields in the presence of catalytic amount of iodine as a catalyst. GRAPHICAL ABSTRACT
PdI2 in DMSO promoted the oxidation of functionalized diarylalkynes into benzil derivatives in excellent yields. This new oxidation reaction was achieved with short reaction times and low loading of palladium catalyst. This efficient catalytic process has been applied successfully to the one-pot construction of a series of nitrogen-containing heterocycles of biological interest according to a tandem oxidation-nitrogen nucleophiles condensation-cyclization. (c) 2008 Elsevier Ltd. All rights reserved.