Ttrans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxalane has been used as new, effective, solid, inexpensive and nontoxic oxidant for in situ generation of Br+ from HBr. This system has been applied as catalyst for synthesis of 2-aryl-1H-benzothiazoles and 2-aryl-1-arylmethyl-1H-benzimidazoles at room temperature in excellent yields and high purity.