In this study, the radical cyclization reactions of cyclic 1,3-dicarbonyl compounds (1a-c) and a, b-unsaturated alcohols (2a-d) through Mn(OAc) 3 were performed. A series of biologically interesting dihydropyrans (3-5) and dihydrofurans (6-18) were synthesized as a result of these reactions. Spiro compounds (19-20) were obtained from the reactions of 1,3-dicarbonyl compounds and (E)-2,4-diphenyl-but-3-en2-ol (2e). The unique structure of compound 19 was also confirmed by X-ray crystallography. In addition, the antibacterial activities of synthesized compounds were screened against some bacteria. Their zone diameters showed better results than some known antibiotics.