Homoconjugated and Spiro Push–Pull Systems: Cycloadditions of Naphtho- and Anthradiquinones with Electron-Rich Alkynes

We report the synthesis and characterization of three new classes of push–pull chromophores using [2+2]-cycloaddition reactions of electron-rich alkynes and electron-poor alkenes. Previous investigations have focused on the reactions of cyano-substituted electron acceptors. This study demonstrates that cyano-free electron acceptors, naphtho- and anthradiquinones, can also be used to access extended push–pull systems. The effects of the structural changes on the spectroscopic and electronic properties were investigated by UV/vis spectroscopy. Structures were confirmed by X-ray and NMR analysis in solution. Keywords: homoconjugation - cycloaddition - push–pull - quinones - spirocyclesSwiss National Science Foundation (Early Postdoc Mobility Fellowship)United States. Air Force. Office of Scientific Research (FA9550-14-1-0226

Iron Catalyzed α-C-H Cyanation of Simple and Complex Tertiary Amines

This manuscript details the development of a general and mild protocol for the α-C-H cyanation of tertiary amines as well as its application in late stage functionalization. Suitable substrates include tertiary aliphatic, benzylic, and aniline-type substrates as well as complex substrates. Functional groups tolerated under the reaction conditions include various heterocycles, as well as ketones, amides, olefins, and alkynes. This broad substrate scope is remarkable, as comparable reaction protocols for α-C-H cyanation frequently occur via free radical mechanisms, and are thus fundamentally limited in their functional group tolerance. In contrast, the presented catalyst system tolerates functional groups that typically react with free radicals, suggesting an alternative reaction pathway. All components of the described system are readily available, allowing implementation of the presented methodology without the need for lengthy catalyst synthesis

Attaching azoles to Hantzsch 1,4-dihydropyridines: Synthesis, theoretical investigation of nonlinear optical properties, antimicrobial evaluation and molecular docking studies

In the present study, we designed three novel compounds via the combination of two precious nitrogencontaining scaffolds; 1,4-dihydropyridine (DHP) and azole, in the same molecule. To synthesize the title compounds, initially, azolyl benzaldehydes were obtained through the nucleophilic aromatic substitution reaction of 4-fluorobenzaldehyde with pyrazole, imidazole or 1,2,4-triazole. Subsequently, an unsymmetrical Hantzsch reaction was applied to achieve DHP scaffold, thus the target molecules. After structural characterization, the effects of various azole rings on optical and non-linear optical (NLO) properties were investigated by computational methods. Band gaps, chemical hardness/softness, dipole moments, average polarizability, first hyperpolarizability values were computed for the target compounds at the CAM-B3LYP/6-31++G(d,p) level of theory. The comparable results confirmed the potential of DHP-azole hybrids to be utilized in NLO devices. The title molecules were further tested for their antibacterial and antifungal activities following the evaluation of their drug likeness properties. The compounds containing imidazole or triazole rings represented better antifungal properties than antibacterial activities. Molecular docking studies were performed in the catalytic site of lanosterol 14 alpha-demethylase, CYP51, from Candida albicans to explain the obtained biological results and suggest molecular modifications to endow this class of molecules with improved antifungal effects

Naphthazarin-Polycyclic Conjugated Hydrocarbons and Iptycenes

The synthesis of a set of naphthazarin-containing polycyclic conjugated hydrocarbons is described herein. Sequential Diels–Alder reactions on a tautomerized naphthazarin core were employed to access the final conjugated systems. Complete conjugation across the backbone can be achieved through complexation with BF₂, as observed by ¹H NMR analysis and UV/vis spectroscopy. Precise synthetic control over the degree of oxidation of naphthazarin quinone Diels–Alder adduct <b>10</b> is additionally demonstrated and enables us to direct its subsequent reactivity. Finally, this work serves to demonstrate the potential for naphthazarin as a building block in the synthesis of novel organic electronic materials

Naphthazarin-Polycyclic Conjugated Hydrocarbons and Iptycenes

The synthesis of a set of naphthazarin-containing polycyclic conjugated hydrocarbons is described herein. Sequential Diels–Alder reactions on a tautomerized naphthazarin core were employed to access the final conjugated systems. Complete conjugation across the backbone can be achieved through complexation with BF₂, as observed by ¹H NMR analysis and UV/vis spectroscopy. Precise synthetic control over the degree of oxidation of naphthazarin quinone Diels–Alder adduct <b>10</b> is additionally demonstrated and enables us to direct its subsequent reactivity. Finally, this work serves to demonstrate the potential for naphthazarin as a building block in the synthesis of novel organic electronic materials

Naphthazarin-Polycyclic Conjugated Hydrocarbons and Iptycenes

The synthesis of a set of naphthazarin-containing polycyclic conjugated hydrocarbons is described herein. Sequential Diels–Alder reactions on a tautomerized naphthazarin core were employed to access the final conjugated systems. Complete conjugation across the backbone can be achieved through complexation with BF₂, as observed by ¹H NMR analysis and UV/vis spectroscopy. Precise synthetic control over the degree of oxidation of naphthazarin quinone Diels–Alder adduct <b>10</b> is additionally demonstrated and enables us to direct its subsequent reactivity. Finally, this work serves to demonstrate the potential for naphthazarin as a building block in the synthesis of novel organic electronic materials

Naphthazarin-Polycyclic Conjugated Hydrocarbons and Iptycenes

The synthesis of a set of naphthazarin-containing polycyclic conjugated hydrocarbons is described herein. Sequential Diels–Alder reactions on a tautomerized naphthazarin core were employed to access the final conjugated systems. Complete conjugation across the backbone can be achieved through complexation with BF₂, as observed by ¹H NMR analysis and UV/vis spectroscopy. Precise synthetic control over the degree of oxidation of naphthazarin quinone Diels–Alder adduct <b>10</b> is additionally demonstrated and enables us to direct its subsequent reactivity. Finally, this work serves to demonstrate the potential for naphthazarin as a building block in the synthesis of novel organic electronic materials

Isoniazid Linked to Sulfonate Esters via Hydrazone Functionality: Design, Synthesis, and Evaluation of Antitubercular Activity

International audienceIsoniazid (INH) is one of the key molecules employed in the treatment of tuberculosis (TB), the most deadly infectious disease worldwide. However, the efficacy of this cornerstone drug has seriously decreased due to emerging INH-resistant strains of Mycobacterium tuberculosis (Mtb). In the present study, we aimed to chemically tailor INH to overcome this resistance. We obtained thirteen novel compounds by linking INH to in-house synthesized sulfonate esters via a hydrazone bridge (SIH1–SIH13). Following structural characterization by FTIR, 1H NMR, 13C NMR, and HRMS, all compounds were screened for their antitubercular activity against Mtb H37Rv strain and INH-resistant clinical isolates carrying katG and inhA mutations. Additionally, the cytotoxic effects of SIH1–SIH13 were assessed on three different healthy host cell lines; HEK293, IMR-90, and BEAS-2B. Based on the obtained data, the synthesized compounds appeared as attractive antimycobacterial drug candidates with low cytotoxicity. Moreover, the stability of the hydrazone moiety in the chemical structure of the final compounds was confirmed by using UV/Vis spectroscopy in both aqueous medium and DMSO. Subsequently, the compounds were tested for their inhibitory activities against enoyl acyl carrier protein reductase (InhA), the primary target enzyme of INH. Although most of the synthesized compounds are hosted by the InhA binding pocket, SIH1–SIH13 do not primarily show their antitubercular activities by direct InhA inhibition. Finally, in silico determination of important physicochemical parameters of the molecules showed that SIH1–SIH13 adhered to Lipinski’s rule of five. Overall, our study revealed a new strategy for modifying INH to cope with the emerging drug-resistant strains of Mt

Synthesis and Optoelectronic Properties of <i>Janus</i>-Dendrimer-Type Multivalent Donor–Acceptor Systems

A convergent, multistep protocol was employed for the synthesis of a <i>Janus</i>-type multivalent donor–acceptor system. The synthetic approach is based on a Sonogashira cross-coupling of two differently ferrocene-(Fc) substituted dendrons and a final sixfold [2 + 2] cycloaddition−retroelectrocyclization (CA−RE) reaction with tetracyanoethene, which occurs regioselectively at only one of the rigidly linked dendrons. The structural and optoelectronic properties of the compounds were investigated by X-ray analysis, UV/vis spectroscopy, and electrochemistry. The target <i>Janus</i>-system displays redox-amphoteric behavior. The nonalkynylated Fc end groups in one dendron are readily and reversibly oxidized. The second dendron, in which the terminal Fc-activated alkynes underwent the CA−RE reaction to give tetracyanobuta-1,3-dienes in the final step of the synthesis, undergoes four reversible 3-e^– reductions in the very narrow potential range of 1 V. A spontaneous intramolecular charge transfer from the donor into the acceptor hemisphere was not observed. Furthermore, the oxidation potential of the Fc donors in one hemisphere is hardly perturbed by the push–pull acceptors in the other, which suggests that electronic communication along the π-system, with several <i>meta</i>-connectivities, is not efficient. Therefore, the charge-transfer bands seen in the <i>Janus</i>-type system originate from the interaction of the Fc donors with the directly connected tetracyanobuta-1,3-diene acceptors in the same hemisphere