“…The addition of water shifts the equilibrium of the condensation reaction in favor to free hydroxyacetone (i. e., a catalytic reaction carried out with 1 in neat n-hexane suppresses the hydrolysis of the acetal (Table 1)), which can further undergo a 1-catalyzed dehydrogenation reaction (Scheme 4, reaction b) giving pyruvaldehyde. The latter compound is known to be a reactive intermediate which undergoes either a base-mediated Cannizzaro reaction [39] to lactic acid (i. e. 1@C K -catalyzed aerobic 1,2-PD (0.274 M) oxidation reaction carried out in the presence of an equimolar amount of NaOH at 140°C for 18 h, gave lactic acid as main reaction product (lactic acid, 50.4 % vs acetic acid, 41.1 %), or reacts with water to give the corresponding pyruvacetal (Scheme 4, reaction c), which then dehydrogenate to give pyruvic acid (Scheme 4, reaction d). The three alcohol dehydrogenation reactions which converts 1,2-PD into PA (Scheme 4, reactions a, b and d) are catalyzed by surface Pd-OH species of 1@C K (XPS evidence), which are transformed into PdÀ H (i. e., Pd-OH reacts with the alcohol to give the corresponding Pd-alcoholate and water and the former undergoes then a Pd-β-hydride elimination reaction giving PdÀ H along with the release of the corresponding carbonyl or carboxyl species).…”