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In the present study, we demonstrated that the introduction of a 1,4-diethyl-1,2,3,4-tetrahydroquinoxalin moiety into the arylidene part of GFP chromophore-derived compounds results in the formation of environment-sensitive fluorogens. The rationally designed and synthesized compounds exhibit remarkable solvent- and pH-dependence in fluorescence intensity. The solvent-dependent variation in fluorescence quantum yield makes it possible to use some of the proposed compounds as polarity sensors suitable for selective endoplasmic reticulum fluorescent labeling in living cells. Moreover, the pH-dependent emission intensity variation of other fluorogens makes them selective fluorescent labels for the lysosomes in living cells. [ABSTRACT FROM AUTHOR]

ortho-Dialkylaminoarylidene malonates undergo hydrogen transfer mediated cyclization in the absence of a catalyst under LED irradiation. This activation mode is found to be relatively general and could be applied to a number of other acceptor motifs in the arylidene substrates tested. Variation of the light source wavelength opens an extra option for fine tuning of the reaction conditions, making the described method almost universal. [ABSTRACT FROM AUTHOR]

In this work, we have shown that the introduction of a trifluoromethyl group into the me-ta-position of arylidene imidazolones (GFP chromophore core) leads to a dramatic increase in their fluorescence in nonpolar and aprotic media. The presence of a pronounced solvent-dependent gradation of fluorescence intensity makes it possible to use these substances as fluorescent polarity sensors. In particular, we showed that one of the created compounds could be used for selective labeling of the endoplasmic reticulum of living cells. [ABSTRACT FROM AUTHOR]

In this work, we showed that the well-known NanoLuc luciferase can act as a fluorogen activating protein for various arylidene-imidazolones structurally similar to the Kaede protein chromophore. We showed that such compounds can be used as fluorescent sensors for this protein and can also be used in pairs with it in fluorescent microscopy as a genetically encoded tag. [ABSTRACT FROM AUTHOR]

A new general approach for the synthesis of azolo[4,5‐b]quinolines via dealkylative TiCl4‐mediated cyclization of 2‐dialkylamino‐arylidene‐azol‐ones upon heating in dichloroethane is found. The reaction scope and limitations are established, showing that at least two different heterocyclic cores could be obtained. Dozen products were obtained in moderate to good yields (22–64 %). [ABSTRACT FROM AUTHOR]

2‐(2‐(Benzylthio)benzylidene)malonates can undergo the 1,5‐hydride shift triggered cyclization resulting in thiachromanes in 45–84 % yield. Boron trifluoride as a reaction promotor is the key to success. DFT calculations revealed that the reaction proceeds via a chelate BF2 complex, which was confirmed by NMR‐analysis. Experimental and theoretical comparison of nitrogen, sulfur and carbon analogues revealed that sulfur derivatives have the highest activation barrier for the hydride transfer due to the unfavorable transition state geometry, which explains the lack of previous reports on 1,5‐hydride shifts in (alkylthio)styrenes. [ABSTRACT FROM AUTHOR]

(1-Alkyltetrahydroquinolin-8-yl)methylidene-1H-imidazol-5(4H)-ones undergo spirocyclization by the action of SnCl4 via 1,5-hydride shift to form spirocyclic julolidine derivatives in 68–97% yields. [ABSTRACT FROM AUTHOR]