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. R
R'
OO R
R''XOO
OOXR'' O2
X = C, S R
R'
OOXR'' R'
O
O
R
R'
a transition state could not be located
6 -11
R''XO
Experimental and computational studies revealed insight into the mechanism addition of a peroxyl radical RʼʼXOO• (where X = C or S) to the alkyne gives a vinyl radical, which is trapped by oxygen subsequent fragmentation of the peroxyl O-O bond with release of an alkoyl radical RʼʼXO• gives a Crigee-type intermediate, which decomposes to the 1,2-diketone this oxidation is the first example for the synthetic application of thiylperoxyl radicals RʼʼSOO• reported in literature.
3
29
-152
-157
22
3
-13 BHandHLYP/6-311G** energies in kJ mol-1 not drawn to scale
-57 -201
