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.
Reaction of 1,1,2,2-Tetrachloro-2,2aα,4α,8bα-tetrahydrocydobuta[<i>c</i>]quinolin-3(1<i>H</i>)-one with Nucleophiles; Reaction, Product Structure, and Mechanism
2a-Substituted dichlorodihydrocyclobuta[c]quinolin-3(4H)-one (3) and trichlorovinyl-2-quinolone (4) were obtained from the cross photocycloadduct of 2-quinolone and tetrachloroethylene. The position of the substituent on 3 was determined from the NOE volumes in the NOESY spectrum in comparison with the AM1 geometries. The reaction of the photoadduct (1) with a base or nucleophile, yielding 3 and/or 4, was interpreted to proceed via a cyclobutene intermediate formation followed by an SN2′ displacement or [2+2] cycloreversion.