5-H-1,2-Oxaphosphole 2-oxides, key building blocks for diversity oriented chemical libraries

CsF-Promoted Iodocyclization of Allenylphosphonates: A Convenient Approach to Highly Functionalized Oxaphospholenes

A convenient CsF-promoted iodocyclization reaction of trisubstituted allenylphosphonates with iodine to construct highly functionalized oxaphospholene derivatives has been developed. A series of readily available starting materials including ferrocenylallenes, aromatic and alkyl substituted allenes can undergo the process successfully.

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

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.