Ketones TPAP catalyst

Typical examples are listed in Table 2.1. A few oxidations are effected by RuO but in general it is too powerful an oxidant for this purpose. The system RuCyaq. NaCl-CCy Pt anode oxidised benzyl alcohol to benzaldehyde and benzoic acid and p-anisaldehyde to p-anisic acid [24], and a wide range of primary alcohols and aldehydes were converted to carboxylic acids, secondary alcohols to ketones, l, -diols to lactones and keto acids from RuOj/aq. NaCl pH 4/Na(H3PO )/Pt electrodes (Tables 2.1-2.4). The system [RuO ] "/aq. K3(S303)/Adogen /CH3Cl3 oxidised benzyhc alcohols to aldehydes [30]. The oxidation catalyst TPAP (( Pr N)[RuO ]) (cf. 1.3.4) is extremely useful as an oxidant of primary alcohols to aldehydes and secondary alcohols to ketones without... 

Isomerization. TPAP is a catalyst that converts allylic alcohols to ketones (8 examples, 41-92%). 

Sparse attention has been paid to the mechanism of perruthenate-catalyzed alcohol oxidations [55]. Although TPAP can act as a three-electron oxidant (Ru " Ru ) the fact that it selectively oxidizes cyclobutanol to cyclobutanone and tert-butyl phenyl-methanol to the corresponding ketone, militates against free radical intermediates and is consistent with a heterolytic, two-electron oxidation [55, 56]. Presumably, the key step involved P-hydride elimination from a high-valent, e. g., alkoxyruthenium (VII) intermediate followed by reoxidation of the lower valent rathenium by dioxygen. However, as shown in Scheme 4.12, if this involved the Ru "/Ru couple the reoxidation would require the close proximity of two ruthenium centers, which would seem unlikely in a polymer-supported catalyst A plausible alternative, which can occur at an isolated mthenium center involves the oxidation of a second molecule of alcohol, resulting in the reduction of mthenium(V) to rathenium(III), followed by reoxidation of the latter to ruthenium (VII) by dioxygen (see Scheme 4.12). 

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