Alakananda Hajra, Ye Wei, and Naohiko Yoshikai
Substituted anilines are common core structures for a wide range of molecules. They are usually synthesised by SNAr chemistry, transition metal-catalysed C-N bond forming couplings or the reduction of nitroarene precursors. The common feature of these methodologies is that the aryl ring is already present in the starting material.
A recent report outlines a more indirect way of preparing such molecules employing a Pd-catalysed dehydrogenative aromatisation of cycloheximines. Rather than sourcing the aryl ring from the starting material, this methodology forms the substituted arene by a dual dehydrogenative catalytic cycle that leads to aromatisation of the cycloheximine substrate.
The use of expensive or wasteful stoichiometric by-products is avoided by using an oxygen atmosphere to achieve successive oxidations. The authors demonstrate the applicability of their method by preparing a variety of substituted anilines.
This method provides an expedient preparation of anilines that complements traditional methods by bypassing possible problems embodied in aromatic substitutions.