Reversible Aminal Formation: Controlling the Evaporation of Bioactive Volatiles by Dynamic Combinatorial/Covalent Chemistry

Dynamic mixtures generated by reversible aminal formation efficiently prolong the duration of evaporation of bioactive volatile aldehydes. Secondary diamines used for the generation of dynamic mixtures are obtained by treatment of primary diamines with carbonyl compounds and reduction of the diimines with NaBH4. The reversibilities of the reactions were demonstrated by NMR measurements in buffered aqueous solutions. Kinetic rate constants and equilibrium constants for the formation and hydrolysis of aminals were determined. The performance of dynamic mixtures as delivery systems for perfumery ingredients was tested after deposition onto cotton, and the long-lastingness of fragrance evaporation was investigated by dynamic headspace analysis against a reference sample. The simplicity of the concept together with its excellent performance makes this delivery system highly interesting for applied perfumery. Reversible aminal formation might also be successfully applicable to dynamic combinatorial/covalent chemistry for screening of pharmaceutically or catalytically active ligands and receptors.