Methyltrioxorhenium Catalyzed Synthesis of Dinitrones from Primary Diamines and Non-Enolizable Aldehydes

Green Chemistry is the design of chemicals and processes that reduce or eliminate the use and generation of hazardous substances, and consequently reduce the risk to human health and the environment. Nitrones have various applications, such as building blocks in the synthesis of natural and biologically active compounds and molecular weight regulators in radical polymerization. In this work, dinitrones were successfully synthesized in a one-pot process from primary diamines and proper aromatic aldehydes employing methyltrioxorhenium (MTO) as catalyst and urea-hydrogen peroxide adduct (UHP) as oxidizing agent. Diamines, such as 1,6-diaminohexane and 1,12-diaminododecane were reacted with benzaldehydes bearing various substituent, such as 4-chloro, 4-nitro, 4-methoxybenzaldehyde, and also furfural. The resulting N,N'-bis (benzylidene)-1,6-hexanediamine N,N'-dioxides or N, N'-bis (benzylidene)-1,12-dodecanediamine N,N'-dioxides (or substituted benzylidenes) were separated with 45-60 % yields. The main advantage of the one-pot process is the elimination of need for several separation and purification steps and reduction in consumption of chemicals and waste production. The products selectively were characterized by H-1-NMR, C-13-NMR, FT-IR spectroscopies, and elemental analysis (CHNS).