Photodimerization of prop-2-en-1-one in the Crystalline Solid State

(E)-3-(2,6-difluorophenyl)-1-(4-methoxyphenyl)prop-2-en-1-one (1) was synthesized and characterized by [sup.1] H and [sup.13] C NMR, mass spectrometry, and single-crystal X-ray diffraction. Photolysis (λ[sub.irr] = 300 nm) of chalcone 1 in the crystalline solid state resulted in the stereospecific formation of the syn-head-to-head photodimer (β-truxinic).