| Abstract
| - Base-promoted cycloaddition reactions of 1-aryl- or 1-aryl-7-substituted-4-oxahepta-1,6-diynesystems in DMSO have proven to involve an anionic intramolecular Diels−Alder process taking place evenat room temperature in spite of the reaction suffering from temporary disruption of aromaticity. Althoughinitially formed α-arylallenide anion can be protonated by DMSO, it can be back to the allenide anion probablybecause of a small acidity difference between α-arylallene and DMSO. The α-arylallenide anion incombination with the α-aryl substituent can constitute an anionic diene structure that undergoes theintramolecular Diels−Alder reaction involving the C(6)-yne part, a very fast process probably because ofthe increased HOMO−1 level of the anionic diene, as shown by DFT calculations. Diversified substitutednaphthalenes, benzofurans, phenanthrenes, and quinolines, including biaryl architectures, are availablefrom 4-oxahepta-1,6-diynes in a highly expeditious way.
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