Abstract
2-Methylenehexahydrocyclobuta[c]quinoline 2 obtained from cyclobuta[c]quinolinespiro-oxetanone 1 was isomerized to 2-methyltetrahydrocyclobuta[c]quinoline 5 by treatment with sodium ethoxide in dry toluene. The reaction of compound 5 with olefins, such as methyl acrylate, acrylonitrile, N-phenylmaleimide, and methyl methacrylate under reflux in dry xylene gave [4+2] cycloadducts, hexahydrophenanthridine derivatives 6-9. Ethoxycarbonylmethyl-cyclobuta[c]quinolines 4 generated by ethanolysis of 1 were treated with thionyl chloride in pyridine to give dehydrated products, (E)-2-(ethoxycarbonylmethylene)cyclobuta[c]quino-line (E)-13 and its isomer (Z)-13. Compounds (E)-13 and (Z)-13 isomerized to the same product, 2-(ethoxycarbonylmethyl)cyclobuta[c]quinoline 14 in the presence of sodium ethoxide in dry benzene at room temperature. Similarly, compound 14 reacted with olefins to give hexahydrophenanthridine derivatives 15-18 via a 2-oxoquinoline-3, 4-diquinomethane intermediate.
