5-Hydroxy-2H-pyrrol-2-ones and not 2-aminofurans are the cycloaddition products between alkyl isocyanides and benzyliden-1,3-diketones

New insights into the cycloaddition reaction between alkyl isocyanides and benzyliden-1,3-diketones are reported. 5-Hydroxy-N-substituted-2H-pyrrol-2-ones and not substituted furans, as previously reported, are formed. The proof of the structure relies on a thorough analytical investigation and X-ray crystallography.