Benzonorbornadiene and 7-oxabenzonorbornadiene were reacted with Meldrum's acid and dimethyl malonate in the presence of Mn(OAc)(3) and Cu(OAc)(2) in acetic acid. The reaction of benzonorbornadiene with Meldrum's acid gave a naphthalene derivative whereas the reaction with dimethyl malonate formed rearranged products derived from a carbocation intermediate. However, the reaction of 7-oxabenzonorbornadiene with Meldrum's acid gave two nonrearranged products. On the other hand, the reaction with dimethyl malonate unexpectedly formed a dihydronapthalene derivative with an unusual structure. The mechanism for the formation of the products is discussed. (C) 2016 Elsevier Ltd. All rights reserved.