New Developments on the Hirao Reactions, Especially from “Green” Point of View

Author(s): Réka Henyecz, György Keglevich*.

Journal Name: Current Organic Synthesis

Volume 16 , Issue 4 , 2019

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Abstract:

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.

Keywords: Hirao reaction, P-C coupling, Pd-catalyst, phosphonates, phosphinates, phosphine oxides, green synthesis.

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Article Details

VOLUME: 16
ISSUE: 4
Year: 2019
Page: [523 - 545]
Pages: 23
DOI: 10.2174/1570179416666190415110834

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