Preparation and plant growth-regulatory activity of N′-chloro-substituted phenyl- and benzyl-N-furfuryloxamides

N'-Chlorophenyl- and N'-chlorobenzyl-N-furfuryloxamides (6b-e and 7b-d) were synthesized through the reaction of chloro-substituted anilines (12b-e) or chloro-substituted benzylamines (13b-d) with N-furfuryloxamic acid sodium salt (10), which was prepared via condensation of methyl oxalate (8) with furfurylamine, followed by hydrolysis of the resulting amide-ester with sodium hydroxide, The activity of the prepared compounds (6 and 7) as plant growth regulators was examined by a germination assay using rape and leek seeds. N'-(3-Chlorophenyl)-N-furfuryloxamide (6c) showed a little effectiveness as an inhibitor, whereas the parent compound, N'-phenyl-N-furfuryloxamide (6a) inhibited the root growth of rape seedlings, The 2-chlorophenyl derivative (6b) inhibited the root growth of rape seedlings as potently as 6a, but sufficiently promoted the root growth of leek seedlings. Further, the 4-chlorophenyl derivative (6d) promoted the root growth of both species. On the other hand, in the series of chlorinated benzyl derivatives (7b-d), N'-(3-chlorobenzyl)-N-furfuryloxamide (7c) showed a markedly superior inhibitory effect in both species, but 2- and 4-chlorobenzyl derivatives (7b and 7d) inhibited the root growth of only rape seedlings.