Palladium−Tetraphosphine as Catalyst Precursor for High-Turnover-Number Negishi Cross-Coupling of Alkyl- or Phenylzinc Derivatives with Aryl Bromides

The system combining the tetraphosphine cis,cis,cis -1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane (Tedicyp) and [Pd(C 3 H 5 )Cl] 2 has been found to be a very active catalyst for the cross-coupling of aryl bromides with alkyl- or arylzinc derivatives (Negishi reaction). A variety of aryl bromides react in good yields and high turnover numbers (TONs) (up to 800 000) with diethylzinc, n -butylzinc bromide, or n -hexylzinc bromide in the presence of 0.1−0.0001 mol % catalyst in most cases.