Isomer Dependence on the Reactivity of Diazenes with Pentaphenylborole

4 years ago

Isomer Dependence on the Reactivity of Diazenes with Pentaphenylborole

Venkata A. K. Adiraju, Caleb D. Martin

Reactions of the anti-aromatic pentaphenylborole with diazenes indicate that both the substitution and the isomer influence the reaction outcome. With respect to trans isomers, azobenzene underwent coordination and C−H addition across the diene of the borole, and 2′,6′-dimethylazobenzene furnished a fused tricyclic system. Under photolytic conditions, both of the aforementioned diazenes generate the first 1,3,2-diazaborepin heterocycles, rationalized through reactivity with the cis isomers. This notion is corroborated by the reaction of pentaphenylborole with benzo[c]cinnoline, the tethered variant of azobenzene, that only exists as the cis conformer as the corresponding 1,3,2-diazaborepin was produced regardless if the reaction is conducted in the dark or light. The more aromatic pyridazine proved to be less reactive, forming a resilient adduct. To B or not to B? Reactions of the anti-aromatic pentaphenylborole with diazenes furnished a range of unique boracycles with the outcome influenced by whether the trans or cis diazene isomer is reacted.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/chem.201702539