Exploring the Potential of Diarylacetylenediols as Hydrogen Bonding Catalysts

In the course of a search for new
classes of hydrogen bonding catalysts,
we have examined diarylacetylenediols as potential catalysts for the
Diels–Alder reaction. General and efficient methods have been
developed for the preparation of these diols. Their structures were
systematically modified, and increased activity was observed for those
possessing an electron-withdrawing group on the aryl groups. The electron-deficient
diarylacetylenediol catalysts, while more active, undergo spontaneous
cyclization to the corresponding benzo­[b]­furans.
A mechanism is postulated to explain this facile transformation. Computational
studies performed on 2-ethynylphenol help to explain the effect of
the alkyne on the conformation and hydrogen bond donating ability
of the adjacent OH group. Finally, the crystal structure of one of
the diols is reported, and it displays an intricate network of intermolecular
hydrogen bonds.