Protonation and cyclization of 1,3-diarylpropynones in superacids

1,3-Diarylpropynones ArCCCOAr in superacids with H ₀ ranging from –20 to – 14 undergo protonation at the carbonyl oxygen atoms to give stable ArCCC(O⁺H)Ar ions or at the acetylenic C² atom with formation of reactive ArC⁺=CHCOAr species. The effects of the Ar and Ar substituents and reaction conditions on the intramolecular cyclization of ArC⁺=CHCOAr to 3-arylinden-1-ones are discussed.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 12, 2004, pp. 1819–1828.Original Russian Text Copyright © 2004 by Vasilev, Walspurger, Pale, Sommer, Haouas, Rudenko.