Benzonorbornadiene and oxabenzonorbornadiene were reacted with dimedone and acetylacetone in the presence of Mn(OAc)(3) and Cu(OAc)(2). The reaction of benzonorbornadiene with dimedone gave the dihydrofuran addition product, whereas the reaction with acetylacetone produced, in addition to the dihydrofuran derivative, a rearranged product. On the other hand, oxanorbornadiene gave unusual products such as the cyclopropanated compound and the product arising from the addition of two moles of dimedone. The mechanism of formation of the products is discussed. (c) 2005 Elsevier Ltd. All rights reserved.