The synthesis and application of monodentate N-substituted heteroarylphosphines is described. In general, the ligands are conveniently prepared by selective metallation at the 2-position of the respective N-substituted heterocycle (pyrrole, indole) by using n-butyllithium/tetramethylethylenediamine (TMEDA) followed by quenching with dialkyl- or diarylchlorophosphines. Of the different ligands prepared, the new dialkyl-2-(N-arylindolyl)phosphines (cataCXium P) perform excellently in the palladium-catalyzed amination of aryl and heteroaryl chlorides. Coupling of both activated and deactivated chloroarenes proceeds under mild conditions (room temperature to 60 degrees C). By using optimized conditions remarkable catalyst productivity (total turnover number, TON, up to 8000) and activity (turnover frequency, TOF=14000 h(-1) at 75% conversion) are observed.

The telomerization reaction of 1,3-butadiene with alcohols to give alkyl octadienyl ethers in the presence of palladium-carbene catalysts has been studied in detail. Unprecedented catalyst efficiency with turnover numbers (TON) up to 1,500,000 and turnover frequencies (TOF) up to 100,000 h(-1) have been obtained after optimization for the reaction of methanol in the presence of an excess of in situ generated carbene ligands. High yields (75-97 %) and catalyst productivities (TON 15,000-100,000) are observed for other aliphatic alcohols and phenols. For comparison five carbene-palladium(0) complexes have been synthesized and characterized by X-ray crystallography. Both electronic and steric effects on the stability and reactivity of the catalysts have been discussed on the basis of density functional theory calculations.

N-Aryl-2-(dialkylphosphino)imidazoles and -benzimidazoles are conveniently prepared in one step from the corresponding heterocycles by selective deprotonation and quenching with chlorophosphines. The novel ligands are easily tunable and show good to excellent performance in palladium-catalyzed Suzuki reactions and Buchwald-Hartwig aminations of aryl and heteroaryl chlorides.

A selective dimerization reaction of 1,3-butadiene in the presence of 2-propanol to give 1,3,7-octatriene has been developed. By modification of palladium carbene catalysts an unexpected selectivity switch from the telomerization to the dimerization product occurred. In applying the 1,3-bis(2,6-diisopropylphenyl)-4,5-dimethyl-3H-imidazolidenylpalladium(0) complex 9, unprecedented catalyst efficiency (TON > 80 000 and TOF > 5000 h(-1)) has been obtained for this transformation. [reaction: see text]

No abstract