Palladium(II) Acetate Catalyzed Reductive Heck Reaction of Enones; A Practical Approach

A surprisingly practical Pd(OAc)(2) or Pd(TFA)(2)-catalyzed reductive Heck reaction between aryl iodides and alpha,beta-unsaturated ketones is described using N,N-diisopropylethylamine (DIPEA, Hunigs base) as the reductant. In general, 1 mol% of Pd(OAc)(2) is sufficient to afford good yields using electron-rich or halogen-substituted aryl iodides. Electron-deficient aryl iodides preferentially give homocoupling. Enones containing aryl or bulky substituents on the beta-carbon react smoothly, producing mainly reductive Heck product, whereas enones with alkyl substituents on the beta-carbon afford a mixture of reductive Heck and Heck product. Deuterium labeling experiments show that the reaction is a bona fide reductive Heck reaction and exclude a Heck reaction-conjugate reduction cascade.