A C-H functionalization strategy for the expedient access to photoreactive chemical probes of commonly found heterocyclic fragments or drug molecules of pharmaceutical relevance is described. A series of aryl glyoxylic acid reagents featuring pendant alkyne or azide clickable handles have been developed for application in the radical-mediated appendage of benzoyl fragments onto simple heteroaromatic fragments, as well as more complex drug-like compounds. This unprecedented strategy of chemical probe synthesis allows for direct access to photoreactive chemical probes without any requirement of fragment pre-functionalization or significant synthetic re-evaluation.