Synthesis of 2a-Substituted Dichlorocyclobuta[<i>c</i>]quinolin-3-one and 3-(Trichloroethenyl)-2-quinolone through the Cross Photocycloadduct of 2-Quinolone and Tetrachloroethylene
2a-Substituted dichlorocyclobuta[c]quinolin-3-one was obtained from the crossphotocycloadduct of 2-quinolone and tetrachloroethylene by the reaction with bases or nucleophiles via cyclobutene formation and intermolecular SN2′ displacement along with trichloroethenyl-2-quinolone via [2+2] cycloreversion of the cyclobutene intermediate.