PHOTOCHEMICAL 2+2 CYCLOADDITION OF 2-CHLORO-1,4-NAPHTHOQUINONE TO ALKENES. A NOVEL SYNTHESIS OF 1,2-DIHYDROCYCLOBUTA[b]NAPHTHALENE-3,8-DIONES

2-Chloro-1,4-naphthoquinone undergoes photochemical 2+2 addition at its 2- and 3-positions to alkenes. An elimination of hydrogen chloride from the adducts provides a facile and general synthetic method of 1,2-dihydrocyclobuta[b]naphthalene-3,8-diones.