An imidazolidin-1-ol, nitrone and oxadiazinane ring-chain-ring tautomeric dynamic combinatorial library

A dynamic combinatorial library (DCL) based on benzylidene exchange reactions between imidazolidin-1-ol, nitrone and oxadiazinane (INO) ring-chain-ring tautomers at room temperature is created. The probable mechanism of the reaction is discussed based on Hammett type correlation analyses. The equilibria in the DCL are defined as interconversion of INOAr-X to INOAr-Y as a result of reactions with the corresponding aldehydes Y-ArCHO and X-ArCHO and are shown to depend on the σ constants of the substituents and are described by a simple equation log KXY = ρσdif + log KXY(X = Y). The prediction of KXY for any INOAr-X and INOAr-Y interconversion requires only the experimental values of ρ and the known Hammett σ constants of the substituents. The effect of Zn(II) and CF3SO3H on the DCL equilibria is also reported.