Improved synthesis of pyridyl–biaryl ring systems via benzidine rearrangements

The acid-catalyzed benzidine rearrangement of diazo compounds is known to involve several rearrangements with the major pathway being a [5,5] sigmatropic rearrangement to provide 4,4′-diaminobiaryls. A limitation of this rearrangement has been poor conversions with pyridyl systems. Herein, we address this long standing issue to furnish hetero-biaryls via a pyridinium salt in the presence of trimethylsilyl iodide.