A facile and highly efficient method for the regioselective synthesis of 1,4-disubstituted 1,2,3-triazoles (β-keto 1,2,3-triazoles) in good to excellent yields from in-situ generated β-ketoazides and terminal alkynes through Cu(I) catalyzed 1,3 dipolar cycloaddition is described. This reaction proceeds smoothly either in water or in a 1:1 mixture of water and acetone at room temperature without use of any additive. The synthesized compounds were screened for their cytotoxicity in A549 (Lung Cancer), HT-29 (Colon Cancer), He La (Cervical Cancer) using MTT assay that exhibited significant cytotoxicity at modest doses.