Preparation and reactions of 3,4-dihydro-1-ethyl-4-methylene-3,3,6,8-tetrachloro-2(1H)-quinolinone and derivatives

The preparation of hitherto inaccessible 3,3-dichloro-3,4-dihydro-1-ethyl-2(1H)-quinolinone derivatives and reaction intermediates is described. Differences between the multiplicities of the 1H-n.m.r. signal for the geminal methylene protons of the 1-ethyl group in the various derivatives are diagnostically useful in structure verification. The 4-methylene-substituted 3,3-dichloro-3,4-dihydro1-ethyl-2(1H)-quinolinone derivatives on heating, undergoes rearrangement to the corresponding 4-chloromethyl-3-chloroquinolinone. Another unusual reaction is the conversion of the 4-chloromethyl-4-chloro-derivative in sulphuric acid into a 4-formylquinolinone. Possible mechanistic pathways are discussed