oxocarboxylic
acids, or alcohol as a reactant for the acylation of aromatic
compounds based on transition metal-catalyzed C−H
activation.4,5 Recently, great attention has been paid to the
use of toluene and its derivatives as acylation reagents, due to
its stability, low toxicity, and ample availability compared to
those of aldehydes and α-oxocarboxylic acids. Patel,6 Kwong,7
Sun,8 and Zhang9 independently realized the regioselective
acylation of 2-phenylpyridine and acetanilide with toluene
derivatives to afford o-acyl-2-phenylpyridines and o-acylacetanilides.
Recently, the Lu10 group reported the acylation of
azobenzene with toluene to afford acylated products. Herein,
we present a highly efficient and regioselective acylation of
azobenzenes with toluene and its derivatives catalyzed by
palladium in the presence of TBHP, leading to a variety of
acylazobenzenes. Both mono- and diacylazobenzene were
obtained simultaneously. Further investigation revealed that
TBHP loading contributed to the distribution of mono- and
dibenzoylated products. To the best of our knowledge, this is
the first case to access dibenzoylated azobenzenes via transition
metal-catalyzed C−H bond activation.