Catalytic oxidations using ruthenium porphyrins - Advances in Catalytic Activation of Dioxygen by Metal Complexes - page 38

1,5-cyclooctadiene gave only bis-epoxide (76%), and cis -1-phenyl-3-penten-
1-yne only gave cis -epoxide (91%). The 3,4,6-tri- O -acetyl- D -glucal was

epoxidized to only (56%), while the

system gave a 3 : 1 mixture of and (see Fig. 15). Of note,

-(amino)epoxides in 87-89%
yields. The system was consecutively reused
four times without detectable leaching of activity, giving for example
epoxide yields of 96, 93, 90, 92 and 91% from styrene. Lowering the Ru
concentration to 0.17 wt.% decreased the yields (e.g. 68% for styrene
oxidation), but the turnover numbers remained high ( for styrene).
The remarkable activity of was attributed to the
ability of MPR to solvate and swell in some organic solvents 152 .
That Ru(II)-porphyrins do not effect deoxygenation of epoxides has
been ascribed to the relatively low oxophilicity of the incipiently formed
Ru(IV)-monooxo species 105 ; thus such species are able to transfer the oxo
ligand to olefins, and data on the amine-oxides donor systems described
above and for related Ru non-porphyrin systems 41,42,155 support such an
inference.
Ruthenium porphyrins in the presence of O-donors complexes are also
capable of cleaving C=C double bonds. Thus a Ru(TDFPP)/TBHP system
can cleave the C=C bond in

were selectively oxidized to threo

to give acetophenone 156 , while

cleavage of trans , trans -1,4-diphenyl-1,3-butadiene by Ru(TDCPP)/TBHP

yields benzaldehyde and cinnamaldehyde 157 . Epoxidation is proposed as the
first step, followed by a TBHP/Ru-porphyrin-mediated fragmentation of the
epoxide. Another example is reaction of a Ru supramolecular system (( ),

essentially Ru(TPP) with two units linked to two trans-phenyl
rings through metheneoxo linkages, Fig. 17) with

16

In a