[15003-43-7] · C14H10Br2N2Pd · Bis(benzonitrile)dibromopalladium(II) · (MW 472.47)
Physical Data: dark brown crystals.
Solubility: sol benzene, methanol.
Form Supplied in: not commercially available.
Preparative Method: prepared in 90% yield by reacting PdBr2 in PhCN with prolonged heating at 100 °C. The reaction mixture is filtered while hot and the filtrate cooled to give a brown precipitate. Additional product is obtained by precipitation with cyclohexane.
Purification: recrystallize from low-boiling petroleum ether.
Handling, Storage, and Precautions: usually prepared just prior to use.
The title reagent (1) catalyzes the codimerization of alkynes and allyl halides under mild conditions to yield substituted 1,4-pentadienes in one step. This provides a very convenient synthetic method for the preparation of halogen substituted mono- and/or dialkenes (eqs 1 and 2).1-3
Metalated (Z)-1-bromo-1-trimethylsilyl-1,4-pentadiene, a 4-pentenoyl anion equivalent, has been prepared by this method. This compound shows great utility in the transformation of alkynylsilanes into carbonyl compounds.
Butyrolactones are prepared conveniently by intramolecular cyclizations mediated by bis(benzonitrile)dibromopalladium(II), as shown in eq 3.4-6
Isomerization of alkenes by the title reagent is specific for double-bond migration with no detectable skeletal rearrangement (eq 4).
Bis(benzonitrile)dibromopalladium(II) promotes amination of terminal alkenes to give, after reduction, high yields of amines (eq 5).8 Internal alkenes may also be aminated, but the yields are moderate to low. The yield of the amination is strongly temperature dependent and, as the temperature increases, there is a steady decrease in the yield.
Bis(benzonitrile)dichloropalladium(II) is similar to reagent (1). They are interchangeable in almost all reactions. The former is more reactive.9
Helen T. Lee
Parke-Davis Pharmaceutical Research, Ann Arbor, MI, USA