Background: The Hirao reaction discovered ca. 35 years ago is an important P–C
coupling protocol between dialkyl phosphites and aryl halides in the presence of Pd(PPh3)4 as the
catalyst and a base to provide aryl phosphonates. Then, the reaction was extended to other Preagents,
such as secondary phosphine oxides and H-phosphinates and to other aryl and hetaryl
derivatives to afford also phosphinic esters and tertiary phosphine oxides. Instead of the Pd(PPh3)4
catalyst, Pd(OAc)2 and Ni-salts were also applied as catalyst precursors together with a number of
mono- and bidentate P-ligands.
Objective: In our review, we undertook to summarize the target reaction with a special stress on the
developments attained in the last 6 years, hence this paper is an update of our earlier reviews in a similar topic.
Conclusions: “Greener” syntheses aimed at utilizing phase transfer catalytic and microwave-assisted
approaches, even under “P-ligand-free. or even solvent-free conditions are the up-to date versions of the
classical Hirao reaction. The mechanism of the reaction is also in the focus these days.