Untersuchungen von Reaktionsmechanismen durch Isotopenmarkierung,IX Zum Ringverengungsmechanismus von 1,4-Benzthiazin-2,3-4H-dion

By¹⁴C-labeling it is shown that the ring contraction reaction of 1,4-benzothiazin-2,3-4H-dione (1), leading via benzthiazol-2-carbonic acid (2) finally to benzthiazole (3), proceeds via hydrolytic opening of the thiolactone-bond in1, irrespectively of H⁺ or OH^– catalysis.

     

Palladium-Catalyzed Synthesis of Arylamines from Diphenyliodonium Tetrafluoroborate and Secondary Amine

The hetero-cross coupling reaction of diphenyliodonium tetrafluoro-borate with secondary amine in the presence of LiNTMS₂ or NaOtBu as base, Pd₂(dba)_3°CHCl₃ as catalyst, and tri-o-tolylphosphine as ligand afforded arylamines at room temperature under mild conditions.     

Selective anion recognition by retarding the cooperative polarization effect of amide linkages

A novel benzthiazole-based fluorescent receptor was synthesized, and its anion recognition properties were compared with those of similarly designed benzimidazole-based receptors. The selectivity of this receptor for the recognition of dihydrogen phosphate is enhanced by employing hydrogen bonding, in which cooperative polarization effect to the carbonyl group of amide linkages is lacking.     

A benzthiazole-based simple receptor in fluorescence sensing of biotin ester and urea

A benzthiazole-based receptor 1 has been designed and synthesized for recognition of biotin ester and urea in CHCl₃ containing 1% CH₃CN. The receptor binds biotin methyl ester and urea with moderate binding constant values and shows significant increase in emission of benzthiazole motif. The emission characteristics of 1 upon complexation clearly distinguishes biotin methyl ester and urea from thiourea and N,N′-dimethylurea. Characterization and sensing properties of the receptor 1 were evaluated by ¹H NMR, UV-vis, and fluorescence spectroscopic methods.     

A benzthiazole-based tripodal chemosensor for Ba recognition under biological conditions

We synthesized a benzthiazole-based chemosensor with mixed S,N donor sites. The binding units are incorporated in a highly flexible tripodal framework which facilitates the complexation of the binding of larger-sized metals. The chemosensor resulted in the sensitive and selective recognition of Ba²⁺ through the enhancement of the fluorescence intensity when studied in a THF/H₂O (8:2, v/v) solvent mixture. The sensor offers an interesting opportunity to monitor Ba²⁺ in biological samples including the cytoplasm of microbes such as Saccharomyces cerevisiae.