Exploring the Reaction Mechanism of C-H Oxidation by Copper-Salen Complexes.

The mechanism of C-H oxidation of propylene (C 3 H 6 ) and 1-phenyl-1-pentyne (C 3 H 7 -C≡C-Ph) by HOOR (R═Me, t Bu) and 3 O 2 by a copper-salen complex was explored by computations. The most noteworthy step is the complexation of two Cu salens to the peroxide to form either the LCuOH/LCuOR pair or an OH-bridged complex LCu(μ-OH)CuL plus OR. The latter pathway involves an avoided crossing of two triplet electronic states. The LCuOH complex can abstract a hydrogen atom from C 3 H 6 and the C 3 H 5 radical plus 3 O 2 forms the complex LCuOOC 3 H 5 . Migration of a hydrogen to the proximal oxygen atom reforms LCuOH and acrolein HC(O)CH═CH 2 .