Pd-PEPPSI-IHept super(Cl): A General-Purpose, Highly Reactive Catalyst for the Selective Coupling of Secondary Alkyl Organozincs

• Published in: Chemistry : a European journal 2016-10, Vol.22 (41), p.14531-14534
• Main Authors: Atwater, Bruce, Chandrasoma, Nalin, Mitchell, David, Rodriguez, Michael J, Organ, Michael G
• Format: Article
• Language: English
• Subjects: Carbenes; Catalysts; Couples; Coupling; Cross coupling; Direct reduction; Insertion; Reagents
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201603603

Dichloro[1,3-bis(2,6-di-4-heptylphenyl)imidazol-2-ylidene](3-chlor opyr idyl)palladium(II) (Pd-PEPPSI-IHept super(Cl)), 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-IHept super(Cl) 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).