A Rh-III-catalyzed C-H allylation of electron-deficient arenes, heteroarenes, and alkenes at room temperature was developed with allyl bromide. The reaction was carried out in diethyl ether without dehydration, and C-H activation was assisted by the directing anionic nitrogen of the aniline-derived amide. Following the allylation, a domino cycling synthesis of 3,4-dihydroisoquinolin-1(2H)-ones with N-bromosuccinimide (NBS) through intramolecular aminobromination of the introduced double bond was achieved.