photochemical route to naphthalenes is presented. The [4+2] cycloaddition takes place between 3-arylynones and arylacetylenes, in which these moieties may be located intwo molecules (intermolecular PDDA, 1) or in the same molecule (intramolecular PDDA, 5 and 9). Especially the latter approach is attractive from a preparative point of view and permits a straightforward access to highly functionalized naphthalenes