Development of new pathways for the oxidative transformation of alkynes into highly reactive carbonyl compounds. Uta Wille, School of Chemistry, The University of Melbourne, Australia. A major goal in synthetic chemistry is the development of oxidation procedures that use the most abundant (and cheapest) oxidant, molecular oxygen, under non-toxic conditions. We have discovered a novel mild and metal-free activation of molecular oxygen that enables transformation of alkynes into 1,2-diketones mediated by peroxyl radicals. Solution and in the gas phase experiments, in combination with computational studies revealed insight into the mechanism of these transformations. Solution phase a) In solution (presence of O2) experiments: Addition of OOXR'' O2 R''XOO R R' peroxyl radicals RʼʼXOO• (X = C X = C, S R R' or S) to alkynes gives vinyl O O radicals, which are trapped by OO OOXR'' oxygen R R' R' R R''XO Subsequent fragmentation of O-O bond with release of an b) In gas phase (absence of O2) alkoyl radical RʼʼXO• gives a Crigee-type intermediate, which decomposes to the 1,2-diketone With X = S: This oxidation is the first example for the synthetic application of thiylperoxyl radicals RʼʼSOO• reported in literature. Gas phase experiments: Identification of intermediates and products and kinetic data (for the first time).
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