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Studies on the use of easily accessible heteroatom-substituted secondary phosphine oxides as preligands for cross-coupling reactions are described. These air-stable sterically hindered phosphine oxides allow for efficient palladium-catalyzed Suzuki- and nickel-catalyzed Kumada-coupling reactions using electronically deactivated aryl chlorides. In addition, they enable nickel-catalyzed coupling reactions of magnesium organyls with aryl fluorides at ambient temperature, and ruthenium-catalyzed coupling reactions of aryl chlorides via C-H bond activation. Finally, the application of modular diamino phosphine chlorides as preligands for a variety of transition-metal-catalyzed C-C and C-N bond formation reactions employing electron-rich aryl chlorides is presented.

[reaction: see text] Air-stable and easily accessible PinP(O)H enables highly efficient palladium-catalyzed Kumada cross-coupling reactions of aryl tosylates. The in situ generated catalyst proved applicable not only to electron-rich and electron-poor carbocyclic tosylates but also to heterocyclic tosylates, such as pyridine and quinoline derivatives. The results described herein constitute the first use of air-stable secondary phosphine oxides as preligands for transition-metal-catalyzed coupling reactions between organometallic species and tosylates.

Two selectively successive I/Cu exchange reactions performed with (Nphyl)CuLi allow the functionalization of indoles in positions 2 and 3. The 2,3-diketones prepared by this method can readily be converted to tricyclic heterocycles by standard methods.