Designed Iron Catalysts for Allylic C−H Functionalization of Propylene and Simple Olefins

Propylene gas is produced worldwide by steam cracking on million‐metric‐ton scale per year. It serves as a valuable starting material for π‐bond functionalization but is rarely applied in transition metal‐catalyzed allylic C−H functionalization for fine chemical synthesis. Herein, we report that a newly‐developed cationic cyclopentadienyliron dicarbonyl complex allows for the conversion of propylene to its allylic C−C bond coupling products under catalytic conditions. This approach was also found applicable to the allylic functionalization of simple α‐olefins with distinctive branched selectivity. Experimental and computational mechanistic studies supported the allylic deprotonation of the metal‐coordinated alkene as the turnover‐limiting step and led to insights into the multifaceted roles of the newly designed ligand in promoting allylic C−H functionalization with enhanced reactivity and stereoselectivity. A new cyclopentadienyliron dicarbonyl complex was discovered to enable the coupling of the allylic carbon of propylene and carbonyl electrophiles. This approach was also successfully applied to allylic C−H functionalization of simple olefins. Experimental and computational studies provided insights into the mechanism and origins of ligand effects on reactivity and diastereoselectivity.