The palladium-catalyzed annulation reaction of terminal alkynes with a silirene offers a general approach to siloles. The use of 2,3-Dithienylsilacyclopropene indeed allows the synthesis of photochromic siloles with a dithienylethene (DTE) backbone in high yields and tolerance to a variety of functional groups.
The reaction was studied using a variety of alkynes bearing a phosphinyl substituent, providing an efficient method for accessing photochromic phosphinosiloles. The influence of the connectivity between the phosphinyl group and the silole backbone was studied in depth, in particular the stereoelectronic effects on the basicity of the phosphorus atom, upon light irradiation, between the closed and open isomers.
In the case of (phosphinoaryl)siloles that incorporate a phenyl linker, conjugation has less influence than sterics, as the open isomer is more basic the closed one.
When directly connected to the silole backbone, a reverse situation is observed due to the substantial conjugation between the phosphine lone pair and the extended p-system of the photochrom in its closed form.
- Akshitha Selvaraj, Marie Cordier, Marc Devillard,* Gilles Alcaraz*
Chem. Eur. J., 2023, http://dx.doi.org/10.1002/chem.202302374
- Marc Devillard, Univ. Rennes, CNRS, ISCR - UMR 6226, F-35000 Rennes, France
marc [dot] devillarduniv-rennes [dot] fr
- Gilles Alcaraz, Univ. Rennes, CNRS, ISCR - UMR 6226, F-35000 Rennes, France
gilles [dot] alcarazuniv-rennes [dot] fr
Published September 1, 2023