Among the approaches to medium sized rings, cycloadditions stand out for their ability to generate these structures in a single step from simple fragments. 1, 2 For example,[4+ 3]- cycloadditions employing oxyallyl units and 1, 3-dienes offer an attractive route to cycloheptane adducts containing several useful handles for further functionalization. 1 We3 and others4 have noted that [4+ 3]-cycloadditions of cyclic oxyallyls provide access to ...
