S. Saito et al., Efficient dehydration of hydroxyenals and -enones: HfCl4 center dot(THF)(2) as an effective catalyst for di-, tri- and tetraene formation, SYNLETT, (11), 2001, pp. 1690-1692
Polyenes were easily obtained from hydroxy(tri, di)ene-containing carbonyl
compounds in good to excellent yields in the presence of catalytic HfCl4. (
THF)(2).