C–H addition reactivity of 2-phenylpyridine and 2,2′-bipyridine with pentaphenylborole

Abstract

The reactions of pentaphenylborole with pyridines with a pendent aryl group in the 2-position, specifically 2-phenylpyridine and 2,2′-bipyridine, readily afforded adducts. Upon thermolysis, the adducts converted to ortho C–H addition products with the two substituents introduced onto the diene on the boracyclic carbon atoms adjacent to boron in a syn fashion. Photolysis of the syn 2-phenypyridine product led to isomerization to the anti conformer which did not readily occur for the 2,2′-bipyridine complex. Such C–H bond reactivity is uncommon for main group elements and provides insight into methodologies to access boron frameworks.