Acceleration of palladium catalyzed C-H activation by various Lewis Acids was demonstrated on the directed ortho-alkenylation and acylation of acetanilide and urea derivatives. The universality of this effect was investigated by the study of different palladium catalysts, directing groups in the aromatic substrates and versatile Lewis acids. Experiments were carried out to monitor the reactions and to compare the behavior and activity of different types of Lewis acids. Kinetic investigation revealed a rate determining C-H activation step, and DFT studies were performed for the explanation of Lewis acid effect on C-H activation. (C) 2016 Elsevier B.V. All rights reserved.