Ascorbic acid and aldehydes: Reaction and Influencing Metals
You would need very strongly reducing compound to be able to reduce ascorbic acid. Aldehydes are not the case.
Ascorbic acid would not reduce aldehydes like ethanal either, as can be seen by comparison of their respective redox potentials below:




Redox system
$E^{\circ} [\pu{V}]$




Ascorbic/dehydroascorbic  acid
+0.35


Ethanal/ethanol
-0.197




Transition d-orbital  metals with multiple possible oxidation numbers very frequently act as redox catalysts. Both neighbour oxidation numbers may be common ( $\ce{Fe^{+III}/Fe^{+II}}$, $\ce{Mn^{+III}/Mn^{+II}}$,
$\ce{Mn^{+IV}/Mn^{+III}}$ ), or one may be uncommon ($\ce{Cu^{+III}/Cu^{+II }, Ag^{+II}/Ag^{+I}}$)
Catalytic effect is often related to the opposite charges of reagents and catalysts. The typical example is reaction of oxalate and permanganate anions, catalyzed by manganese cations.
A good metal catalyst has standard redox potential comparable with respective redox potentials of the oxidant a/o reductant.
E.g  $\ce{Ag+}$ may act as a catalyst during oxidation by peroxodisulphate, as $\ce{Ag^2+/Ag+}$ has the similar redox potential. Similarly, $\ce{Mn^2+}$ ions act as the catalyst during  oxidation of oxalic acid  by permanganate in acidic solutions, as $\ce{Mn^2+/Mn^3+}$ has similar redox potential as $\ce{MnO4-/Mn^2+}$.