Lyudmila V. Parfenova

Synthesis and conversions of metallocycles. 22. NMR studies of the mechanism of Cp2ZrCl2-catalyzed cycloalumination of olefins with triethylaluminum to form aluminacyclopentanes

The mechanism of cycloalumination of olefins under the action of AlEt3 in the presence of Cp2ZrCl2 giving rise to aluminacyclopentanes was investigated by dynamic 1H and 13C NMR spectroscopy. The bimetallic complex Cp2ZrEtCl–AlEt3 is formed initially and is converted into the bridged complex Cp2Zr(Cl)CH2CH2AlEt2 as a result of beta-hydride shift and elimination of the ethane molecule. The resulting complex adds a molecule of the initial olefin yielding aluminacyclopentanes. Under the action of Et2AlCl in the presence of an excess of AlEt3, zirconacyclopentanes give rise to intermediate bimetallic complexes stable at -70 °C. Under the reaction conditions, the latter compounds are converted into aluminacyclopentanes.

Synthesis and transformations of metallacycles: 27.* Quantum-chemical study of the mechanism of styrene catalytic cyclometallation with triethylaluminum in the presence of Cp2ZrCl2

Cyclometallation of olefins with AlEt3 in the presence of Cp2ZrCl2 affording five-membered monosubstituted cyclic organoaluminum compounds, was studied by the semiempirical quantum-chemical PM3 method. The proposed model of catalytic cycloalumination of styrene catalyzed by Cp2ZrCl2 is in a good accordance with experimental data obtained by dynamic NMR spectroscopy.

Synthesis and modifications of alkyne derivatives of dihydroquinopimaric, maleopimaric, and fumaropimaric acids

Reactions of maleopimaric and dihydroquinopimaric acid chlorides with propargyl alcohol and propargylamine afforded new terminal diterpene alkynes, and Sonogashira cross-coupling of the latter with 4-iodonitrobenzene led to the formation of arylalkynyl derivatives of Diels–Alder adducts of levopimaric acid.

Synthesis and antimicrobial activity of quinopimaric and maleopimaric acids

A number of nitrogen-, bromine-, and sulfur-containing derivatives of diene adducts of levopimaric acid have been synthesized. The testing of the compounds on Staphylococcus aureus and Klebsiella pneumoniae bacteria has shown that the compounds possess a weak antimicrobial activity.

Cycloalumination of allylbenzenes with triethylaluminum in the presence of Cp2ZrCl2. One-pot synthesis of 2-benzylbutane-1,4-diols as precursors of dibenzylbutane lignans

One-pot synthesis of 2-[(hydroxy- and methoxyphenyl)methyl]butane-1,4-diols in an overall yield of 60–65% by cycloalumination of allylbenzenes (4-allyl-1-methoxybenzene, 4-allyl-1,2-dimethoxybenzene, 5-allyl-2-methoxyphenol, and 5-allyl-1,2,3-trimethoxybenzene) with triethylaluminum in the presence of Cp2ZrCl2 is reported for the first time. The developed procedure opens a new synthetic route to practically important β-substituted butane-1,4-diols that are precursors to dibenzylbutane lignans.

Alkene and Olefin Functionalization by Organoaluminum Compounds, Catalyzed with Zirconocenes: Mechanisms and Prospects

Alkene and olefin functionalization via addition of electro‐ or nucleophilic reagents is one of the convenient synthetic methods for the insertion of heteroatoms into organic molecules. The use of organometallic reagents in these reactions in combination with the specific catalysts provides high substrate conversion and process selectivity. The intro‐ duction of this approach into the chemistry of organoaluminum compounds leads to the development of chemo‐, regio‐ and stereoselective catalytic methods of alkene and ole‐ fin functionalization. The chapter focuses on the modern concepts of the alkene hydro‐, carbo‐ and cycloalumination mechanisms, that is, the experimental and theoretical data on the intermediate structures involved in the product formation, the effects of the cata‐ lyst and organoaluminum compound structure, reaction conditions on the activity and selectivity of the bimetallic systems. The prospects of the development of enantioselec‐ tive methods using these catalytic systems for the alkene and olefin transformations are considered.

Convenient one-pot synthesis of resin acid Mannich bases as novel anticancer and antifungal agents

AbstractThe one-pot three-component CuCl-catalyzed aminomethylation of the abietane diterpenoid propargyl esters by formaldehyde and secondary amines was studied for the first time. The novel diethylamino, pyrrolidine, and morpholine-substituted butynyl derivatives of abietic, dehydroabietic, levopimaric, maleopimaric and dihydroquinopimaric acids were obtained. It was shown that synthesis of the abietic acid propargyl ester by the reaction of the abietane diterpenoid with oxalyl chloride and dimethylformamide is accompanied by the formylation of the ring B at the C-7 position and the dehydrogenation of the ring C to form the dehydroabietic acid ester. The cytotoxic, antibacterial and fungicidal activities of the synthesized compounds were studied in vitro. The experimental results showed that the most promising compound was 7-formyl abietic derivative Mannich base with a pyrrolidine substituent, with an MIC of 16 μg/ml against methicillin-resistant S. aureus ATCC 43300, and 8 μg/ml against C. albicans ATCC 90028 and 4 μg/ml against C. neoformans H99; ATCC 208821. The dihydroquinopimaric acid derivative with the diethylamine fragment showed the greatest antiproliferative activity towards twelve tumor cell lines.

One-pot synthesis of 1,2,3-triazole derivatives of maleopimaric and dihydroquinopimaric acids

Effective one-pot synthesis of 1,2,3-triazole derivatives of maleopimaric and dihydroquinopimaric acids consists in the reaction of diterpene propargyl esters with organic azides generated in situ in the presence of СuI catalyst.

Triboluminescence of zirconium η5-complexes

This work describes a comparative study of tribo- and photoluminescence of metallocenes (Cp2HfCl2, Cp2TiCl2, Cp2ZrCl2, (CpMe)2ZrCl2, rac-Me2C(3-But-Cp)2ZrCl2, Ind*2ZrCl2). Occurring under mechanodestruction of polycrystals, triboluminescence of zirconium bis-cyclopentadienyl complexes, Cp2ZrCl2, (CpMe)2ZrCl2, and rac-Me2C(3-But-Cp)2ZrCl2 has been revealed for the first time. The triboluminescence spectrum in air is similar to the photoluminescence spectrum of zirconocene polycrystals. The triboluminescence spectrum does not show *N2 luminescence. Ne and Ar lines are observed in the triboluminescence spectrum in the atmosphere of these gases. An increase in the number of substituents in zirconocene ligands leads to a bathochromic shift of the emission band maximum in triboluminescence spectra of the complexes. Possible mechanisms of zirconocene triboluminescence excitation are discussed.