Catalysis of the addition of benzenethiol to 2-cyclohexen-1-ones by uranyl-salophen complexes: A catalytic metallocleft with high substrate specificity

The base induced addition of benzenethiol to 2-cyclohexen-1-one and its 4,4 -, 5,5- and 6,6-dimethyl derivatives is catalysed by a salophen-uranyl base d metallocleft 2 in chloroform solution with high turnover efficiency and l ow product inhibition. Analysis of rate data coupled with equilibrium measu rements for complexation of the catalyst with the enone reactants and addit ion products shows that the catalytic mechanism involves the three main ste ps typical of single-substrate enzymatic processes, namely substrate bindin g and recognition, transformation of the bound substrate, and release of th e reaction product. Unlike the reference salophen- uranyl 1, catalyst 2 is endowed with a structured binding site responsible for a high degree of sub strate specificity among the investigated enones, due to recognition of the ir shape and size.