Transformations of functional groups, such as OCH2Ph, OCOPh, NO2 and I, in 1,3,5-triphenyl-6-oxoverdazyls 1a-1e were investigated in order to expand the range of synthetic tools for incorporation of the verdazyl system into more complex molecular architectures and to increase spin delocalization. Thus, Pd-catalyzed debenzylation of the OCH2Ph group or basic hydrolysis of the OCOPh group gave the phenol functionality, which was acylated, but could not be alkylated. Orthogonal deprotection of diphenol functionality was also demonstrated in radical 1c. Pt-catalyzed reduction of the NO2 group led to the aniline derivative, which was acylated. Attempted C-C coupling reactions to iodophenyl derivatives 1e and 5e were unsuccessful. Selected verdazyl radicals were characterized by EPR and electronic absorption spectroscopy, and results were analyzed with the aid of DFT computational methods.

A series of 19 structurally diverse C(3)substituted derivatives of benzo [e][1,2,4]triazine were synthesized from 3-chloro-(1c) and 3-iodobenzo[e][1,2,4]triazine (1d) obtained in three steps from 2-nitroaniline in 37−55% yields. Nucleophilic aromatic substitution and metal-catalyzed (Pd, Cu) reactions led to functional derivatives that include alkyl (C 5 H 11 ), (het)aryl (Ph, 2-thienyl, ferrocenyl), ArCC, amine (NHPh and morpholine), PO(OEt) 2 , sulfanyl (SBu-t), alkoxide (OEt, OMe), and CN. The synthesis of C(3)−CF 3 derivative 1g via the Ruppert reaction with 1d and its 1-oxide analogue 2d led to the substitution followed by formal addition of HCF 3 to the CN bond. Pd-catalyzed carbonylation reactions of 1d and 2d did not give the corresponding C(3)-carboxylic acids. Therefore, acid 1f was obtained through hydrolysis of the CN. The substituent effect on the electronic structure of the benzo[e][1,2,4]triazine ring was investigated by spectroscopic methods (UV−vis and NMR) augmented with density functional theory calculations. Results show significant effect of the C(3) substituent on the π−π*(1) transition energy and good correlation of the 1 H NMR chemical shift with the substituent constant σ p . Molecular and crystal structures of six derivatives were established with the single-crystal X-ray diffraction method, and the substituent impact on the molecular geometry was investigated.

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Stable and non-odorous alkyl ferrocenyl thioketones react with bis(4-methoxyphenyl)diazomethane according to the 'two-fold extrusion' reaction principles, and tetrasubstituted ethylenes obtained thereby can be demethylated to give (Fc,2OH)-ferrocifens in good yields. The method offers an alternative approach to this class of medically relevant compounds. A similar protocol with alkyl ferrocenyl thioketones and selected diaryldiazomethanes leads to ferrocenyl-substituted ethylenes including dibenzofulvenes. These products are of potential interest for electrochemical and photophysical studies.

The reaction of a series of stable alpha-chlorinated oligosulfanes 2 and 3 with [Pt(eta(2)-C(2)H(4))(Ph(3)P)2] 1 have been investigated. Starting with the alpha-chlorodisulfanes 2 a,b, the platinum dichloride complex 5 and the side-on bonded thioketone platinum complexes 6 a,b were formed. Complex 1 was treated with corresponding trisulfanes 3 a,b to give 5, 6 a,b and the dithiolatocomplexes 7 a,b. We assume that the {Pt(0)(Ph(3)P)2}-complex fragment inserted along the S--S bond to form the unstable intermediate G, which decomposed to form the products described above. We could prove that the sterically crowded 1,2,4-trithiolane 8 was not involved in the reaction pathway by treatment of 1 with 8 under the same conditions; after 24 h, 8 was found to be unreacted. X-ray structure analyses were performed on complexes 6 a, 7 a and 7 b.

The influence of the substitution pattern in ferrocenyl α-thienyl thioketone used as a proligand in complexation reactions with Fe3(CO)12 was investigated. As a result, two new sulfur–iron complexes, considered [FeFe]-hydrogenase mimics, were obtained and characterized by spectroscopic techniques (1H, 13C{1H} NMR, IR, MS), as well as by elemental analysis and X-ray single crystal diffraction methods. The electrochemical properties of both complexes were studied and compared using cyclic voltammetry in the absence and in presence of acetic acid as a proton source. The performed measurements demonstrated that both complexes can catalyze the reduction of protons to molecular hydrogen H2. Moreover, the obtained results showed that the presence of the ferrocene moiety at the backbone of the linker of both complexes improved the stability of the reduced species.

Condensation of diacetyl monooxime with formaldimines derived from alkoxyamines in glacial acetic acid at room temperature leads to corresponding 2-unsubstituted imidazole N-oxides bearing an alkoxy substituent at the N(1) atom of the imidazole ring. Subsequent O-benzylation afforded, depending on the type of alkylating agent, either symmetric or nonsymmetric alkoxyimidazolium salts considered as structural analogues of naturally occurring imidazole alkaloids, lepidilines A and C. Some of the obtained salts were tested as precursors of nucleophilic heterocyclic carbenes (NHCs), which in situ reacted with elemental sulfur to give the corresponding N-alkoxyimidazole-2-thiones. The cytotoxic activity of selected 4,5-dimethylimidazolium salts bearing either two benzyloxy or benzyloxy and 1-adamantyloxy groups at N(1) and N(3) atoms was evaluated against HL-60 and MCF-7 cell lines using the MTT (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) assay. Notably, in two cases of alkoxyimidazolium salts, no effect of the counterion exchange (Br− → PF6−) on the biological activity was observed.

A straightforward access to 2-unsubstituted imidazole N -oxides with subsequent deoxygenation by treatment with Raney-nickel followed by N -benzylation opens up a convenient route to lepidilines A and C. Both imidazolium salts were used to generate in situ the corresponding imidazol-2-ylidenes, which smoothly reacted with elemental sulfur, yielding imidazole-2-thiones. These reactions were performed either under classical conditions in pyridine solutions or mechanochemically using solid Cs 2 CO 3 as a base. The structure of lepidiline C was unambiguously confirmed by X-ray analysis of its hexafluorophosphate. An analogous protocol toward lepidilines B and D and their 4,5-diphenyl analogues is less efficient due to observed instability of the key precursors, i.e., the respective 2-methylimidazole N -oxides. Comparison of cytotoxic activity against HL-60 and MCF-7 cell lines of all lepidilines, as well as their selected structural analogues (e.g., 4,5-diphenyl derivatives and PF 6 salts), revealed slightly more potent activity of the 2-methylated series, irrespectively of the type of counterion present in the imidazolium salt. Remarkably, the well-known 1,3-diadamantylimidazolium bromide (the “Arduengo salt”), known as the precursor of the first, shelf-stable NHC representative, and its adamantyloxy analogue displayed the most significant cytotoxic activity in the studied series.