Base-promoted cycloaddition reactions of 1-aryl-or 1-aryl-7-substituted-4-oxahepta-1, 6- diyne systems in DMSO have proven to involve an anionic intramolecular Diels-Alder process taking place even at room temperature in spite of the reaction suffering from temporary disruption of aromaticity. Although initially formed α-arylallenide anion can be protonated by DMSO, it can be back to the allenide anion probably because of a small ...
