1-Indenyldialkylphosphines and Cyclopentadienyldialkylphosphines as Ligands for High-Activity Palladium-Catalyzed Cross-Coupling Reactions with Aryl Chlorides

The reactions of three deprotonated indenes (1,2,3-trimethyl, 1,2,3,4,7-pentamethyl, and 1,2,3-trimethyl-4,7-dimethoxy) and the lithium salt of pentamethylcyclopentadiene (Cp*) with ClPR 2 (R = i Pr, Cy) resulted in the formation of six indenylphosphines and two cyclopentadienylphosphines, isolated as the respective phosphonium salts. The Pd−phosphine complexes, formed in the presence of Na 2 PdCl 4, base, and coupling partners, were shown to be highly active Pd complexes for various aryl chloride cross-coupling reactions. Quantitative yields in the Suzuki coupling are possible with 0.05−0.1 mol % of catalyst. Aryl chlorides can be coupled in quantitative yields in the Sonogashira reaction using 1 mol % of catalyst complex, while the Buchwald−Hartwig reaction typically requires 0.5 mol % of catalyst. In addition to the standard substrates, ferrocenylamine was subjected to Buchwald−Hartwig aminations, resulting in ferrocenylarylamines in near-quantitative yield.