Moifying the 5-position of thieno[2,3-d][1,2,3]thiadiazole-6-carboxylate derivatives

Thieno[2,3-d][1,2,3]thiadiazole-6-carboxylates 3 belong to a new group of p lant protecting agents as highly potent inducers of systemic acquired resis tance (SAR). In order to obtain an enhanced basis set for structure activit y relationship studies several modifications of the heteroaromatic core wer e performed by introduction of various substituents. One approach utilizing metallation techniques led to several 5-substituted derivatives 4a-h of th e title compound. Using the chloro-compound 5 obtained via this route the a bility to undergo nucleophilic substitution reactions was investigated, rep resenting a complementary strategy towards derivatives 6a-c.