Covalent hydration catalysis

In NaOD-D20 (or with added DMSO) 1,2,4-triazine and its 5- or 6-methyl and 5-phenyl derivatives exchange H-3 for deuterium with an opposite reactivity order to that observed under acid catalysis (vide supra) (73T2495). The observation that the 5-phenyl derivative reacts 15 times faster than the unsubstituted parent (Table 10.4 comparison was made in D,0-DMS0 because of solubility problems) clearly indicates that the carbanion mechanism operates in basic media rather than a process involving covalent hydration. 

Oxygen nucleophiles The enantioselective addition of water to enones in an aqueous environment, catalysed by a copper complex with an achiral ligand, non-covalently bound to DNA has been reported to produce the corresponding )8-hydroxy ketones with <82% ee. Deuterium labelling demonstrated that the reaction is diastereospecific, with only the S yn-hydration product formed, for which outcome, there is no equivalent in conventional homogeneous catalysis ... 

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