Acetonaphthones I (R = H, R1 = CN; R = MeO, R1 = H; R = H, R1 = MeO) and 2-morpholinoacrylonitrile undergo [2+2]- or [4+2]-photocycloaddn. depending on the substituents. Thus, I (R = MeO, R1 = H) gave only the [4+2] cycloadduct, but [2+2] cycloadducts were obsd. with I (R = H, R1 = CN; R = H, R1 = MeO). I (R = H, R1 = Br) underwent photosubstitution. The endo or exo orientation of the morpholino group in the cycloadducts was detd. by x-ray crystal structure anal. and NOE expts.