Chemoselectivity Switching through Coupled Equilibria

Complex mixtures are found in biological and petrochemical feedstocks, and in the primordial soup implicated in the origins of life. Reacting individual compounds within these mixtures is challenging because of the difficulty in controlling the chemoselectivity of such reactions. We show that the selectivity of imine oxidation can be controlled within doubly dynamic combinatorial libraries, wherein two coupled equilibria determine whether the most oxidizable aldehyde precursor is made available to the oxidant or sequestered away from it. Under the slow oxidation conditions, the most electron-rich precursor can traverse the shallow energy landscape and its oxidation product dominates the final mixture. Faster oxidation captures the imine mixture composition, favoring the products derived from electron poorer push-pull imines.