Reaction between alkyl isocyanides and dibenzoylacetylene in the presence of strong NH-acids: synthesis of highly functionalized aminofurans

Protonation of the highly reactive 1:1 intermediates produced in the reaction between alkyl isocyanides and dibenzoylacetylene by saccharin, phthalimide, or 4-methyl-5-nitroimidazole, leads to vinylnitrilium cations, which undergo carbon-centered Michael type addition with the conjugate base of the NH-acid to produce highly functionalized aminofuran derivatives.