TADDOL-based P,S-bidentate phosphoramidite ligands in palladium-catalyzed asymmetric allylic substitution

A series of easy-to-prepare and modular chiral P,S-bidentate phosphoramidites were synthesized. With respect to Pd(II), these ligands showed the ability to form stable P,S-chelate allylic complexes. The structures of the ligands and their complexes were confirmed by 2D NMR spectroscopy and single-crystal X-ray diffraction. These chiral inducers provided up to 99% ee in the Pd-catalyzed asymmetric allylic substitution of (E)-1,3-diphenylallyl acetate with C- and N-nucleophiles and up to 94% ee in the Pd-mediated allylic alkylation of cinnamyl esters with β-ketoesters and 2,5-dimethylpyrrole. Furthermore, up to 92% ee with quantitative conversion and chemo- and regioselectivity was achieved in the rare reaction between 2-(diethoxyphosphoryl)-1-phenylallyl acetate and aniline. The effects of the structural parameters, reaction conditions and ligand-to-metal ratio on the catalytic results are discussed. It was shown that the ligands surpass their analogues with different denticity.

Meso-Formyl, Vinyl, and Ethynyl Porphyrins-Multipotent Synthons for Obtaining a Diverse Array of Functional Derivatives

This review presents a strategy for obtaining various functional derivatives of tetrapyrrole compounds based on transformations of unsaturated carbon-oxygen and carbon-carbon bonds of the substituents at the meso position (meso-formyl, vinyl, and ethynyl porphyrins). First, synthetic approaches to the preparation of these precursors are described. Then diverse pathways for the transformations of the multipotent synthons are discussed, revealing a variety of products of such reactions. The structures, electronic, and optical properties of the compounds obtained by the methods under consideration are analyzed. In addition, there is an overview of the applications of the products obtained. Biomedical use of the compounds is among the most important. Finally, the advantages of using the reviewed synthetic strategy to obtain dyes with targeted properties are highlighted.

Diverse “roof shaped” chiral diamidophosphites: palladium coordination and catalytic applications

“Roof shaped” chiral diamidophosphites of various structures and denticities were obtained and tested in Pd-catalyzed asymmetric allylic substitution.

Carbene functionalization of porphyrinoids through tosylhydrazones

Here, we investigated methods for carbene functionalization of porphyrinoids through metal catalyst-free thermal decomposition of their tosylhydrazones. For the first time, tetrapyrrolyl substituted carbenes were obtained via thermolysis of tosylhydrazones of the corresponding tetrapyrrolyl aldehydes and ketones in the presence of a base. The carbenes formed reacted thermally with substrates without a metal catalyst or light irradiation. Carbenes at the β-pyrrolic position of porphyrinoids reacted with styrene leading to cyclopropane derivatives of tetrapyrroles. Carbenes also reacted with 1,4-dioxane with their insertion into the C-H bond yielding a tetrapyrrole 1,4-dioxane conjugate. Thermolysis of tosylhydrazones of meso-formyl-β-octaalkylporphyrinoids led exclusively to the corresponding cyclopentane fused porphyrinoids via intramolecular carbene C-H insertion. A plausible reaction mechanism was discussed based on DFT calculations of the intermediates. The tetrapyrrolyl carbenes were found to be considerably more stable than other carbenes. The products of the functionalization of porphyrinoids via hydrazone formation and subsequent carbene reactions exhibited modified optical spectra. The method for carbene functionalization of porphyrinoids through thermal decomposition of their tosylhydrazones created a new synthetic pathway for tailoring the perimeter of tetrapyrrolic macrocycles. Moreover, this method allows the obtainment of dyes with controllable spectral optical properties. In particular, new tetrapyrrole derivatives possessing phytoporphyrin carbon skeletons which have not been accessible were obtained using a convenient straightforward procedure.

Copper(i) halide and palladium(ii) chloride complexes of 4-thioxo[1,3,5]oxadiazocines: synthesis, structure and antibacterial activity

The first copper(i) and palladium(ii) complexes containing monastrol analogs, 4-thioxo[1,3,5]oxadiazocine derivatives, have been synthesized. The complexes demonstrated significant antibacterial activity in contrast to free heterocyclic thiones.

The selective hydrosilylation of norbornadiene-2,5 by monohydrosiloxanes

A simple one-step approach for the selective synthesis of exo-norbornenes with organosilicon substituents is suggested through the direct hydrosilylation of norbornadiene-2,5 with chlorine-free silanes. Using the example of norbornadiene-2,5 hydrosilylation with pentamethyldisiloxane and 1,1,1,3,5,5,5-heptamethyltrisiloxane, the possibility of obtaining exo-isomers of norbornenes with 100 exo-/endo-selectivity is shown. The investigation of Pt-, Rh-, and Pd-complexes in combination with various ligands as catalysts was performed. The hydrosilylation of norbornadiene-2,5 in the presence of Pt- or Rh-catalysts was not selective and led to a mixture consisting of three isomers (exo-/endo-norbornenes and substituted nortricyclane). In the case of the Pd-salt/ligand catalytic system, the formation of an endo-isomer was not observed at all and only two isomers were formed (exo-norbornene and nortricyclane). The selectivity of exo-norbornene/nortricyclane formation strongly depended on the nature of the ligand in the Pd-catalyst. The best selectivity was revealed when R-MOP was the ligand, while the highest catalytic activity was reached with a dioxalane-containing ligand.

A simple one-step approach for the selective synthesis of exo-norbornenes with organosilicon substituents is suggested through the direct hydrosilylation of norbornadiene-2,5 with chlorine-free silanes.

Correction: The selective hydrosilylation of norbornadiene-2,5 by monohydrosiloxanes

Correction for ‘The selective hydrosilylation of norbornadiene-2,5 by monohydrosiloxanes’ by Marina A. Guseva et al., RSC Adv., 2019, 9, 33029–33037.

Structural explanation of the spectral features of the nonsymmetrical complex {2,3,7,8,12,13,17,18-octaethyl-5-[(methylimino)methyl]porphyrinato-κ4N21,N22,N23,N24}palladium(II)

The features of porphyrins defining their functionality are related to their conformational flexibility. The degree of nonplanarity of metalloporphyrins depends directly on the number of substituents, their size and their location. The introduction of substituents in the meso positions of β-substituted porphyrins increases the steric interaction and leads to distortions of the porphyrin core. Increasing the distortion of the porphyrin core would augment the bathochromic (red) shift of the electronic absorption spectra. A new nonsymmetrical 2,3,7,8,12,13,17,18-octaethyl-5-[(methylimino)methyl]porphyrin complex of palladium(II), [Pd(C₃₈H₄₇N₅)], was synthesized and characterized by NMR, mass spectrometry and X-ray analysis. The features of the electronic absorption spectrum of the synthesized complex are explained by the planarity of the porphyrin core and the π-system of the imino group orthogonal to it.

Polymeric structure of a coproporphyrin I ruthenium(II) complex: a powder diffraction study

Porphyrin complexes of ruthenium are widely used as models for the heme protein system, for modelling naturally occurring iron-porphyrin systems and as catalysts in epoxidation reactions. The structural diversity of ruthenium complexes offers an opportunity to use them in the design of multifunctional supramolecular assemblies. Coproporphyrins and metallocoproporphyrins are used as sensors in bioassay and the potential use of derivatives as multiparametric sensors for oxygen and H⁺ is one of the main factors driving a growing interest in the synthesis of new porphyrin derivatives. In the coproporphyrin I Ru^II complex catena-poly[[carbonylruthenium(II)]-μ-2,7,12,17-tetrakis[2-(ethoxycarbonyl)ethyl]-3,8,13,18-tetramethylporphyrinato-κ⁵N,N',N'',N''':O], [Ru(C₄₄H₅₂N₄O₈)(CO)]_n, the Ru^II centre is coordinated by four N atoms in the basal plane, and by axial C (carbonyl ligand) and O (ethoxycarbonylethyl arm from a neighbouring complex) atoms. The complex adopts a distorted octahedral geometry. Self-assembly of the molecules during crystallization from a methylene chloride-ethanol (1:10 v/v) solution at room temperature gives one-dimensional polymeric chains.