A study of the rearrangement of N-chloro-derivatives of cyclic amides and related compounds

Abstract

Optimum conditions for the aluminium chloride-catalysed conversion of cinnamanilide to carbostyril have been established and a reaction pathway for this cycloelimination is proposed. Furthermore, the scope of the reaction as a synthesis of derivatives of carbostyril, and subsequently of derivatives of 2-chioroquinoline, has been examined with particular attention given to chloro- and methyl- derivatives. An improved synthesis of derivatives of 3,4-dihydrocarbostyril is reported and a limitation of an existing synthesis of derivatives of oxindole is noted. A qualitative determination of the products from the hydrogen chloride-catalysed rearrangement of both if- chi oro carbostyril and N,-6-di chloro carbostyril showed that 6-chlorocarbostyril and 3,6'dichlorocarbostyril were formed from the former N-chloroamidev and 3,6-dichIorocarbostyril from the latter. These results are shown to be fully consistent with the 'Orton' mechanism established for the rearrangement of other if-chloro amides. The kinetics and products of the photolytic rearrangement of N-chloro-carbostyril has been investigated. Some of the results could be satisfactorily explained by analogy with the mechanisms known to operate in the rearrangement of N-chloroacetanilide. However, anomalies were found to exist connected with the unexpected ease of formation of hydrogen chloride during the photolysis of N-chlorocarbostyril. Carbostyril itself was found to dimerise under the conditions used to rearrange its N-chloro-derivative. Comparative studies of the photolyses of N-chlorocinnamanilide, N-chloro-3-phenylpropionanilide, N-chloro-3,dihydrocarbostyril and N-chloro-if-phenyl-3,4-dibydrocarbostyril were also conducted together with preliminary studied of the photolyses of N,6-dichiorocarbostyril and N-chloro-oxindole. A new explanation is offered of the ability of1359213592N-chloro-3.4-dihydrocarbostyril and N-chloro-4-phenyl-3,dihydro carbostyril to undergo dehydrochlorination on photolysis. A brief preliminary study has also been made of the benzoyl peroxide induced rearrangement of N-chlorocarbostyril in benzene.