In the present study, a novel synthetic strategy to directly produce versatile 3-acylindoles through Rh(III)-catalyzed C-H activation and annulation cascade of N-phenylamidines with α-Cl ketones was developed, in which α-Cl ketones serve as unusual one-carbon (sp3) synthons. This strategy features high regioselectivity, efficiency, wide substrate tolerance, and mild reaction conditions, which further underscore its synthetic utility in drug molecule synthesis.