A modular and efficient method for the synthesis of α-substituted 1,2-dihydroquinolines is described. Under mild metal-free conditions, readily available N-carbamoyl 1,2-dihydroquinolines undergo oxidative C-H alkynylation, alkenylation, and allylation with a range of potassium trifluoroborates using TEMPO oxoammonium salt as an oxidant.