Synthesis and Evaluation of Antioxidant Properties of Novel 2‐[2‐(4‐chlorophenyl) benzimidazole‐1‐yl]‐N‐(2‐arylmethylene amino) acetamides and 2‐[2‐(4‐chlorophenyl) benzimidazole‐1‐yl]‐N‐(4‐oxo‐2‐aryl‐thiazolidine‐3‐yl) acetamides‐I