Pd-PEPPSI-IPent^Cl – Selective Coupling of Secondary Organozinc Nucleophiles

Key words

palladium - zinc - PEPPSI - organcozinc reagents

Significance

The authors report the new catalyst Pd‑PEPPSI‑IPent^Cl, which highly efficiently couples secondary alkylzinc reagents to (hetero)aryl bromides, chlorides and triflates. The corresponding alkylated aromatics are obtained in excellent yield and with high regioselectivity.

Comment

β-Hydride elimination (BHE) constitutes one of the main drawbacks for the cross-coupling of secondary alkyl reagents, especially if they react with electron-rich coupling partners. These problems are overcome by the new palladium-catalyst, which bears bulkier substituents and additionally, is characterized by a decreased electron density, thus favoring reductive elimination instead of BHE. Density functional theory (DFT) calculations support the theoretical selectivities.