Oxidative C–H/C–H Cross-Coupling of (Hetero)arenes Enabled by Intrinsic Aldehydes as Directing Groups: Discovery of Multicolor Lipid Droplet Bioprobes

oxidative C-H/C-H cross-coupling of (hetero)arenes has been unlocked, representing a conceptually distinct alternative to transient directing group-based approaches. This transformation features broad substrate scope and functional-group tolerance, affording diverse 3-formyl bi(hetero)aryls. The directing role of aldehyde is confirmed by X-ray diffraction of a cyclometalated Cp*Ir(III) intermediate. Moreover, synthetic utility is demonstrated by selective multicolor imaging of lipid droplets in cells and turbid tissues, underscoring potential for fatty liver disease diagnosis.