N0 -(2-Chloroquinolin-3-yl)methylidene-4-hydroxy-2H-1,2-benzothiazine-3-carbohydrazides 1,1-dioxide (4a–4j) were prepared starting from corresponding methyl 4-hydroxy-2H-1,2-benzothiazine-3-carboxylate (1a and 1b) by condensation with hydrazine hydrate, followed by treatment with substituted 2-chloro-3-formyl quinolines (3a–3e) under ultrasonic irradiation. On the other hand, substituted 2-chloro-3-formyl quinolines were prepared in a facile way from respective acetanilides under microwave irradiation in very short duration of time (1.5–3.0 min) obtaining excellent yields. The compounds (4a–4j) were tested for their superoxide scavenging and antimicrobial activities. Almost all the compounds showed moderate superoxide scavenging activity and compounds 4a, 4d, 4g, and 4j were found active against gram-positive bacterial strains. In addition, 4a, 4e, and 4i were active against fungi (Aspergillus flavus, Aspergillus niger, Fusarium oxysporum).