The ligand-free Pd-mediated reaction between styrene and a 6-bromo-2,2-diaryl-2H-benzopyran proceeded anomalously to give a 2-(diarylmethyl)-5-styrylbenzofuran via a tandem Heck coupling - ring-contraction process; none of the styryl substituted 2,2-diaryl-2H- benzopyran was observed. A 2,2-diaryl-6-styryl-2H-benzopyran resulted from the condensation between 4-hydroxystilbene and a 1,1-diarylpropynol and which exhibited photochromism through the reversible electrocyclisation of the pyran unit; no isomerisation - electrocyclisation of the stilbene moiety was detected.
|Number of pages||6|
|Journal||Dyes and Pigments|
|Publication status||Published - 1 Feb 2012|