1,2-Dihydrocyclobuta(c)quinoline.

Using 1, 2-dihydrocyclobuta [c] quinolin-3(4H)-one (III) obtained through the photoaddition of 4-methoxy-2-quinolone (I) to ethylene and subsequent base treatment of the resulted cycloadduct (II) as a key intermediate, 1, 2-dihydrocyclobuta [c] quinoline (V), a new aza-analogue of naphthocyclobutene, was synthesized.