H/D exchange of β-carbonyl esters inhibited by cucurbit[7]uril

Hydrogen/deuterium (H/D) exchange at the α-H of β-carbonyl esters has been used as a useful probe to demonstrate the kinetic aspects of cucurbit[7]uril-catalyzed processes. The rate constants for H/D exchange of ethyl acetoacetate (1), methyl acetoacetate (2) and dimethyl malonate (3) have been determined in the absence and presence of cucurbit[7] uril by ¹H NMR spectroscopy. H/D exchange at the α-H of β-carbonyl esters is inhibited by cucurbit[7]uril in D₂O, where the inhibitory factor order methyl acetoacetate > ethyl acetoacetate > dimethyl malonate, is in good agreement with the order of their binding constants. In the previous research, the models are oftentimes restricted to positively charged substrate. We now extend this research to neutral substrates, hence demonstrating further the versatile applications of cucurbiturils in the field of supramolecular catalysis.