Synthesis of Primary Arylamines Using Bulky Palladium N-heterocyclic Carbene Precatalysts

The reaction between aryl halides and ammonia was investigated using N-heterocyclic carbene (NHC) ligated palladium pre-catalysts. The use of NHCs is well documented for coupling of alkyl and arylamines, but there is little precedent for the coupling of ammonia. A new, rationally designed, pre-catalyst (DiMeIHeptCl)Pd(allyl)Cl featuring highly-branched alkyl chains has been shown to be effective in selective aminations across a range of challenging substrates, including nitrogen-containing heterocycles and those featuring base-sensitive functionality. The less bulky Pd-PEPPSI-IPentCl pre-catalyst performs well for ortho substituted aryl halides giving monoarylated products in high yield with good selectivity.