N-1- and N-2-Anthryl Succinimide Derivatives: C–N Bond Rotational Behaviors and Fluorescence Energy Transfer

Cascade [4 + 1] Annulation through Activation of the C(sp2)-H Bond Enabling Benzothiadiazinoisoindolcarboxylate, Benzothiadiazinoisoindole, and Benzothiadiazinoisoindolepyrrolidinedione as Hybrid Spiro-Heterocyclic Frameworks†

Two structurally distinct and biologically privileged succinimide and isoindole heteroarenes bearing benzothiadiazinedioxide motif-centered hybrid conjugates are proficiently achieved through Rh(III)-catalyzed sequential C(sp2)-H bond activation, ortho-alkenylation and finally cascade intramolecular cyclization. The significant feature of this developed protocol is that the resulting diversely decorated heterocycles contain a quaternary carbon center and this has been coursed through atypical [4 + 1] annulation ignoring the prevalent [4 + 2]-cyclization pathway and interestingly the applied coupling partners (e.g., maleimide, maleate, and styrene) to materialize the protocol functioned only as C1 synthon. Furthermore, the selective reduction strategy enables to modify the hybrid conjugate of succinimide and benzothiazine dioxide to benzothiazine dioxide-based spirocyclic isoindolopyrrolidinedione skeleton following preferential reduction of one carbonyl group of imide functionality. Overall this methodology emerges to be easily handled, versatile, time-efficient, and manifests relatively unfamiliar spiro-cyclization and good functional group tolerance so easy to grab a library of the entirely new variant of decorated hybrid spiro-heterocyclic scaffolds.

Fluorescent sensor based on triphenylamine for Zn2+ with high selectivity and imaging in living cells

It is of great importance to design a fluorescent sensor with high selectivity, sensitivity and large Stokes shift to zinc detection for environmental water sample and in vivo. Herein, A novel Zn²⁺ fluorescent sensor with larger Stokes shift (110 nm) 1-((5-(4-(diphenylamino)phenyl)pyridine-2-imino)methyl)naphthalene-2-ol (abbr. TPA-PN) was designed and synthesized. In DMF-H₂O (V: V = 1: 1, pH = 7.0) solution, it could achieve high selectivity and sensitivity to Zn²⁺, there was a linear responsive range of 0-20 μM of concentration of Zn²⁺ ions for the sensor, the detection limit was as low as 19.134 nM and the binding constant was calculated to be 3.24 × 10⁴ M^-1. The species of TPA-PN and zinc were clarified at different pH. Besides, the interaction properties and fluorescence mechanism were demonstrated by the species theory, density functional theory (DFT) calculation, ¹H NMR titration, FT-IR and MS. Most importantly, it provided a new real-time, on-site method and showed excellent potential in-vivo imaging ability.

Translational isomers of N-sulfonylated [3]catenane: synthesis and isomerization

N-Sulfonylated [3]catenanes, which exist as two translational isomers, were synthesized. The X-ray crystal structure of the distal isomer of [3]catenane, which has higher symmetry, revealed hydrogen bonds involving the carboxylic acid moieties on the terminal rings. The thermodynamic parameters of the isomerization revealed that this hydrogen bonding influenced the isomerization process.

Unusual regio- and stereo-selectivity in Diels-Alder reactions between bulky N-phenylmaleimides and anthracene derivatives

Unusual regio- and stereo-selectivity in Diels-Alder (D-A) reactions were achieved between bulky N-phenylmaleimides and anthracene derivatives. Using multiple substituents with steric hindrance on both diene and dienophile, a noticeable shift toward 1,4-addition was successfully obtained. The substrate scope in this reaction was broad and the highest yield of anti-1,4-adducts was over 90%. Novel structures of anti-1,4-adducts were confirmed by single crystal X-ray diffraction analysis. This study not only provides the first reported method of synthesizing anti-1,4-adducts and achieving otherwise unattainable regio- and stereo-selectivity, but also elucidates the importance of combining the steric effects of two reactants to shift products toward 1,4-adducts. Moreover, the resulting 1,4-adducts could be further functionalized through their halogen groups via carbon-carbon coupling reactions.

Enantioselective copper-catalyzed azide-alkyne click cycloaddition to desymmetrization of maleimide-based bis(alkynes)

A copper catalyst system derived from TaoPhos and CuF2 was used successfully for catalytic asymmetric Huisgen [3+2] cycloaddition of azides and alkynes to give optically pure products containing succinimide- and triazole-substituted quaternary carbon stereogenic centers. The desired products were obtained in good yields (60-80 %) and 85:15 to >99:1 enantiomeric ratio (e.r.) in this click cycloaddition reaction.