Efficient regioselective synthesis of novel fully substituted pyrazoles has been achieved through Huisgen cycloaddition reaction of δ-acetoxy allenoates with hydrazonoyl chlorides by the addition of Ag2O. The present approach offers the advantages of simpleness, high efficiency, mild conditions, wide substrate scope, and good-to-excellent regioselectivities. The strategy could be performed on a large-scale pattern to allow access to structurally versatile pyrazoles, of which a key intermediate of lonazolac (303), a nonsteroidal anti-inflammatory drug, could be synthesized efficiently. Moreover, several pyrazoles show obvious growth-inhibitory activity of Huh-7 cells, expected as potential anticancer agents.