Selective Synthesis of Unsymmetric Dibenzo[a,e]pentalenes by Rhodium-Catalysed Stitching Reaction

K. Takahashi, S. Ito*, R. Shintani*, K. Nozaki*
Chem. Sci. 2017, 8, 101–107.  DOI: 10.1039/C6SC04560J

Abstract: A rhodium-catalysed stitching reaction between 2-(silylethynyl)arylboronates and 2-(silylethynyl)aryl bromides has been developed for the synthesis of unsymmetric dibenzo[a,e]pentalenes. The introduction of appropriately sized silyl groups on the starting substrates led to a high crossover selectivity without using an excess amount of either substrate. The present stitching reaction could produce a variety of unsymmetric dibenzo[a,e]pentalene derivatives, including those with electronically different substituents on the fused benzene rings as well as heteroarene fused compounds. Desilylative halogenation was also demonstrated to synthesise the corresponding halogenated dibenzo[a,e]pentalenes, which can be used as building blocks for further chemical transformations.

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