Cover Picture: (Adv. Synth. Catal. 2-3/2010)

The cover picture, provided by David W. C. MacMillan, shows a dual-catalytic aldehyde alkylation via photoredox organocatalysis in which electrophilic radicals (derived from the photoredox cycle; above) combine with facially biased enamine intermediates (derived from the organocatalytic cycle; below). The photoredox catalyst, Ru(bpy)₃²⁺ readily accepts a photon from a visible light source to populate the *Ru(bpy)₃²⁺ metal-to-ligand charge transfer (MLCT) excited state, eventually enabling single-electron transfer (SET) with an alkyl halide to furnish the electron-deficient alkyl radical. Simultaneously, the organocatalytic cycle is initiated upon condensation of the imidazolidinone catalyst (inset) exclusively with a non-substituted aldehyde to form a stereochemically-defined enamine. The two activation pathways merge in the key alkylation step via rapid addition of the electrophilic radical to the π-rich olefin followed by a series of concerted steps which return the organocatalyst and photocatalyst to their respective cycles and render the optically enriched α-alkyl aldehyde.