Fluorescent aggregates of a cyano-substituted phenylenevinylene derivative (R-1) have been used as a bimodal probe for the easy and fast detection of CO2.
Development of small‐molecule‐based multi‐luminescent fluorophores utilizing simple synthetic methodologies, as well as easily available starting materials, has gained much attention in recent years. Herein, we disclose an efficient protocol for the synthesis of N‐protected 1H‐indazole derivatives with diverse substituents at their 3‐ and 5‐positions via palladium‐catalyzed reactions of hydrazones and p‐benzoquinones. The obtained 1H‐indazole derivatives can be easily modified into donor‐acceptor (D−A)‐type chromophores (Indazo‐Fluors) with tunable emission properties in both solid and solution state. Owing to the extent of intramolecular charge transfer, Indazo‐Fluors exhibit positive solvatochromic emission spanning from blue‐green to orange‐red. Theoretical studies were undertaken to rationalize the observed trends in the optical properties of Indazo‐Fluors. Finally, a triethylene glycol (TEG) appended Indazo‐Fluor exhibiting a large Stokes shift and low cytotoxicity allowed us to use it for cell imaging.
An efficient, metal‐free synthesis of pyrazoles and chromenopyrazoles from aldehyde hydrazones and acetylenic esters has been developed. A library of molecules with diverse functional groups has been synthesized using substituted hydrazones and alkynes, both symmetrical and unsymmetrical ones. The derivatives were isolated in moderate to good yields.
Indazole is an important heterocyclic scaffold exhibiting a wide range of biological and pharmacological properties and plays a crucial role in drug design. In recent years, indazoles have gained attention in materials chemistry owing to their promising photophysical properties. The biomedical importance and natural rarity inspire the development of new practical syntheses of the indazole core. In this review, we are presenting a comprehensive overview of recent developments in the transition metal-catalyzed synthesis of indazole during the last decade.
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