A modular synthesis of a new family of core-fluorinated BODIPYs was elaborated. β-Fluoro-β-nitrostyrenes were used as starting materials to prepare a set of mono-fluorinated pyrrole-2-amides using the Barton-Zard reaction with 2-isocyanoacetamides. The prepared monofluorinated building blocks were successively transformed into the corresponding dipyrromethanes and 1,7-difluoro-BODIPY-3,5-diamides. As a result, a new family of luminophores with a combination of fluorescence and photosensitizing properties was obtained. The photophysical properties of novel BODIPYs were studied by UV-vis and fluorescence spectroscopy, cyclic voltammetry and DFT calculations. In addition, their ability to generate singlet oxygen was assessed. The properties of 1,7-difluoro-BODIPY-3,5-diamides were compared with their analogues to reveal the substituent effect at the 3,5-positions. The fluorescent properties of the obtained dyes were significantly improved in comparison to their 3,5-diester analogous.
A catalyst-free synthesis of N2,C3-substituted 2 H -indazoles from readily available N -anilinoindoles has been elaborated using a C-to-N transmutation molecular editing strategy.
Reactivity of non-aromatic 2,5-dichloro-2H-pyrroles toward S-nucleophiles was investigated. It was found that these non-aromatic derivatives exhibit both oxidative and electrophilic properties. Their reaction with thiols and xanthates proceeds as redox process to form disulfides and 5-chlorinated pyrroles as a result of 2,5-dichloro-2H-pyrroles reduction. However, the reaction with ammonium thiocyanate afforded the corresponding 5-thiocyanated 1H-pyrroles. Based on these findings, a novel one-pot method for the thiocyanation of 2,3,4-trisubstituted pyrroles was developed. The protocol involves the in situ generation of highly reactive 2,5-dichloro-2H-pyrroles via dearomative chlorination of the corresponding pyrroles using trichloroisocyanuric acid (TCCA). Subsequent addition of ammonium thiocyanate leads to regioselective incorporation of a thiocyanate group at the C5 position and rearomatization of the pyrrole core. A broad scope of pyrrole-5-thiocyanates was obtained in yields up to 82%. Furthermore, these derivatives were efficiently transformed into 5-trifluoromethylthiolated pyrroles using Ruppert’s reagent in up to 94% yield. This reaction sequence provides a cost-effective way to obtain 5-trifluoromethylthiolated pyrroles, avoiding the need for high-cost electrophilic reagents. The synthetic utility of these novel sulfur-containing pyrrole derivatives was also demonstrated.