Room temperature iron-photopromoted arene C–H alkenylation without Grignard reagents

<p>Iron is inexpensive, non-toxic, and the most abundant transition metal in the earth's crust, rendering iron-catalysed C–H activations attractive yet particularly challenging. Despite major advances, iron-catalysed C–H activations have been linked to high reaction temperatures or the use of reactive Grignard reagents. Here, we present iron-catalysed ketimine C–H activations at ambient reaction temperature with the help of blue light in the absence of additives, utilising easily accessible <i>cis</i>-[Fe(H)2(dppe)2] (dppe = 1,2-bis(diphenylphosphino)ethane) as a single component precatalyst. Mild reaction conditions, high atom economy, and the lack of Grignard reagents are distinguishing features of the iron-catalysed C–H alkenylation manifold. Detailed mechanistic investigations by deuterium labelling, isolation of organometallic intermediates, and in operando LED-NMR spectroscopy revealed the role of the light and an oxidative addition to an iron(0) complex as the modus operandi for the C–H activation</p>