Pd-PEPPSI-IHeptCl: A General-Purpose, Highly Reactive Catalyst for the Selective Coupling of Secondary Alkyl Organozincs

Dichloro[1,3‐bis(2,6‐di‐4‐heptylphenyl)imidazol‐2‐ylidene](3‐chloropyridyl)palladium(II) (Pd‐PEPPSI‐IHeptCl), a new, very bulky yet flexible Pd–N‐heterocyclic carbene (NHC) complex has been evaluated in the cross‐coupling of secondary alkylzinc reactants with a wide variety of oxidative addition partners in high yields and excellent selectivity. The desired, direct reductive elimination branched products were obtained with no sign of migratory insertion across electron‐rich and electron‐poor aromatics and all forms of heteroaromatics (five and six membered). Impressively, there is no impact of substituents at the site of reductive elimination (i.e., ortho or even di‐ortho), which has not yet been demonstrated by another catalyst system to date. One catalyst fits all! Pd‐PEPPSI‐IHeptCl has emerged as a “one‐catalyst‐fits‐all” candidate for the selective coupling of secondary alkylzinc reagents with a wide selection of aromatic and five‐ and six‐membered ring heteroaromatic oxidative addition partners. Impressively, hindered 2,6‐disubstituted oxidative addition partners couple with no migratory insertion, verifying the high rate of reductive elimination with this catalyst (see scheme).