Novel push–pull butadienes derived from 1,1-diaryl-2-propyn-1-ols and 1,1,1,5,5,5-hexafluoro-2,4-pentanedione: Synthesis, absorption spectra and solvatochromic behaviour

Butadiene dyes were synthesized by the catalytic C–C coupling of 1,1-diaryl-2-propyn-1-ols with 1,1,1,5,5,5-hexafluoro-2,4-pentanedione. The reaction, which was promoted by the 16e− (η3-allyl)-ruthenium(II) complex [Ru(η3-2-C3H4Me)(CO)(dppf)][SbF6], involved the Meyer–Schuster rearrangement of the aromatic alkynol and subsequent aldol-type condensation of the resulting enal with the fluorinated β-dicarbonyl compound. The absorption spectra of the dyes, as well as their solvatochromic behaviour, were studied; the structure of (4-C6H4OMe)2CCH–CHC(COCF3)2 was unambiguously confirmed by means of single-crystal X-ray diffraction.