Diels-Alder (DA) reactions result in the formation of two carbon-carbon bonds of six-membered ring structures with high atom economy. The use of unsaturated organoboranes, which are widely available and exhibit low toxicity, enables the modulation of reactivity and selectivity in these reactions and also allow a variety of subsequent transformations the carbon-boron bond. These characteristics align these reactions with the principles of green chemistry.
Recently, boron-substituted furans have been employed as dienes in DA reactions with activated dienophiles, demonstrating high reactivity. These reactions are particularly appealing as their precursors are derived from biomass. Specifically, the reaction of potassium 3-furanyltrifluoroborate with N-phenylmaleimide in acetonitrile led to a mixture of endo/exo cycloadducts after one hour at room temperature, which could be easily purified through solvent washes. In contrast, the tetrabutylammonium analog yielded the exo product exclusively. The use of bismaleimides as dienophiles resulted in double cycloaddition after one day at room temperature, with variable endo/exo ratios.
In recent years, self-healing polymeric materials (SHPMs) have attracted much attention. These sustainable polymers can restore their mechanical properties through dynamic covalent bonds. Due to their thermal reversibility, the DA reactions between furan and different bismaleimides have been widely used in the design of SHPMs. Based on our previous results, we have proposed that boron-substituted furans could be employed in the design of novel SHPMs with multiple dynamic covalent bonds.