Synthesis and Cyclization of Photochromic Bisarylindenones

Significance

Diarylethenes are an important and well-established class of thermally irreversible photochromic compounds. The authors show that they can diversify the properties of a photochrome by annulating the central double bond to an easily modifiable functional group. Open photochromes 3 O and 4 O were synthesized in one step from the corresponding symmetrical diarylacetylenes through a Pd-catalyzed ring-closing reaction with 2-methoxycarbonylphenylboronic acid. A third photochrome, 5 O, was generated by acetalization of 3 O with 1,2-ethanediol.