Reported herein is the first example of a direct arylation of heteroarenes by a transient-ligand-directed strategy without the need to construct and deconstruct the directing group. A wide range of heteroarenes undergoes the coupling with diverse aryl iodides to assemble a large library of highly selective and functionalized 3-arylthiophene-2-carbaldehydes. This route provides an opportunity to rapidly access new mechanofluorochromic materials. Moreover, a novel strategy for mechanochromic luminogens with chromism trends of red- and blue-shifts has been disclosed for the first time by facile functional-group modifications to a common structural core.

Transition metal-catalyzed direct C-H bond functionalization enabled by transient ligands has become an attractive topic. Here we report a palladium-catalyzed site-selective arylation of β-C(sp)-H bonds in aliphatic ketones with β-alanine as the transient ligand.