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 ClPR2 (R = iPr, 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 Na2PdCl4, 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.