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 introduction of this approach into the chemistry of organoaluminum compounds leads to the development of chemo‐, regio‐ and stereoselective catalytic methods of alkene and olefin 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 catalyst and organoaluminum compound structure, reaction conditions on the activity and selectivity of the bimetallic systems. The prospects of the development of enantioselective methods using these catalytic systems for the alkene and olefin transformations are considered

Phytotoxic Potential of Onopordum acanthium L. (Asteraceae)

Onopordum acanthium L. (Asteraceae) is a plant native to southern Europe and southwestern Asia, but it is invasive in disturbed areas and agricultural fields around the world, causing many agronomic problems by interfering with crops or preventing animals from grazing on pastures. Allelopathy could be one of the reasons that this plant has spread over different continents. The aim of the present study was to bioprospect O. acanthium leaf extracts through the isolation and purification of allelopathic secondary metabolites with phytotoxicity to explain their invasive behavior. Phytotoxic activity was tested using etiolated wheat coleoptiles. The most active extract was selected to perform a bioassay-guided isolation of two flavonoids, pectolarigenin (1) and scutellarein 4’-methyl ether (2), and two sesquiterpene lactones, elemanolide 11(13)-dehydromelitensin b-hydroxyisobutyrate (3) and acanthiolide (4). All compounds were isolated for the first time from O. acanthium, and acanthiolide (4) is described for the first time. Compound 3 strongly inhibited the growth of wheat coleoptiles and 1 showed an intermediate effect. The results indicate that these compounds could contribute to the invasion of O. acanthium in ecological systems and agricultural fields

Operation Allelopathy: An Experiment Investigating an Alternative to Synthetic Agrochemicals

Synthetic herbicides represent a serious problem in modern agriculture because they are not biodegradable and can accumulate in the soil and in the groundwater, a situation that allows them to enter the trophic chain and ultimately leads to human exposure. Allelopathic chemicals offer an effective alternative to the synthetic compounds. The aim of this experiment is to highlight the differences between chemical and biological control of diseases in crops and to demonstrate the use of natural fungicides and herbicides as alternatives to synthetic chemicals. The experiment involves an evaluation by students of the potential of plant extracts as an alternative to synthetic agrochemicals to identify new ecological farming techniques that could be applied in agriculture. In an effort to encourage 1800 students in high school (14 to 16 years old) to have an interest in science, technology, and innovation, the third edition of the Summer Science Campus was organized by the Spanish Foundation for Science and Technology and the Ministry of Education, Culture, and Sports with support from the foundation Obra Social “la Caixa”

Current Trends in the Synthesis of Practically Important Five-Membered Boracarbocycles by Transmetalation of Aluminacarbocycles with Boron Halides

The data obtained by the authors in the field of chemistry of substituted borolanes and 2,3-dihydro-1H-boroles are summarized. The authors developed a selective method for the synthesis of five-membered boracarbocycles via transmetalation of aluminacarbocycles, obtained by the catalytic cycloalumination of unsaturated compounds (terminal olefins or acetylenes) with AlEt3 in the presence of Cp2ZrCl2 as a catalyst by boron halides (BF3·Et2O, BCl3, and BBr3). Some examples of the use of this approach to modify steroid compounds (in particular, to introduce a borolan fragment into them) are described in this review

Approach to the Synthesis of Five-Membered Organophosphorus Compounds via Alumoles and Alumolanes

This work summarizes the results of a new approach to the synthesis of previously undescribed, hard-to-obtain five-membered cyclic organophosphorus compounds: 3-alkyl(aryl)-substituted phospholanes, α,ω-bisphospholanes, polycyclic phospholanes, 4,5-dialkyl(diaryl)-disubstituted 2,3-dihydrophospholes, as well as their oxides and sulfides. Alumoles and alumolanes synthesized by the reaction of cycloalumination of available unsaturated compounds (terminal alkenes, α,ω-alkadienes, norbornene derivatives, symmetrical internal alkynes) with Et3Al in the presence of a Cp2ZrCl2 catalyst were used as precursors. The substitution of aluminum atoms in cyclic organoaluminum compounds for phosphorus atoms takes place using alkyl(aryl)phosphorus (III) dichlorides. The developed one-pot method gives high yields of products under mild conditions

Ti-Catalyzed Reaction of β-Pinene with BF₃·THF

The reaction between β-pinene and BF3·THF in the presence of the catalytic system Cp2TiCl2/Mg was carried out for the first time to obtain a 1-fluoro-substituted boraspirane, undescribed previously. The reaction proceeds stereoselectively, but is complicated by the rearrangement of the β-pinene under the Ti-catalyzed reaction conditions

Ti-Catalyzed Reaction of β-Pinene with BF3·THF

The reaction between β-pinene and BF3·THF in the presence of the catalytic system Cp2TiCl2/Mg was carried out for the first time to obtain a 1-fluoro-substituted boraspirane, undescribed previously. The reaction proceeds stereoselectively, but is complicated by the rearrangement of the β-pinene under the Ti-catalyzed reaction conditions

Cyclic 1H-Phospolane Oxides as a Potential Candidate for Cancer Therapy

Organophosphorus compounds have been investigated for agricultural and medicinal applications for decades, and a considerable number of phosphorus-containing drugs have achieved commercial success. A recent review by P. Finkbeiner et al. has shown that phosphine oxides and related phosphorus-containing functional groups are valuable polar structural elements and that they deserve to be considered as a routine part of every medicinal chemist’s toolbox. A new approach to the synthesis of previously hard-to-obtain 3-alkyl-1H-phospholanes oxides was developed by us. In order to assess the potential of five-membered cyclic organophosphorus compounds in cancer therapy, we carried out docking 3-buthyl-1H-phospholanes oxide and 2,3-dihydrophosphole in the binding site of 24 human proteins involved in oncogenesis processes. Proteins were selected using the PharmMapper in-house pharmacophore model database. The results are presented in the article

Cyclic 1H-Phospolane Oxides as a Potential Candidate for Cancer Therapy

Organophosphorus compounds have been investigated for agricultural and medicinal applications for decades, and a considerable number of phosphorus-containing drugs have achieved commercial success. A recent review by P. Finkbeiner et al. has shown that phosphine oxides and related phosphorus-containing functional groups are valuable polar structural elements and that they deserve to be considered as a routine part of every medicinal chemist’s toolbox. A new approach to the synthesis of previously hard-to-obtain 3-alkyl-1H-phospholanes oxides was developed by us. In order to assess the potential of five-membered cyclic organophosphorus compounds in cancer therapy, we carried out docking 3-buthyl-1H-phospholanes oxide and 2,3-dihydrophosphole in the binding site of 24 human proteins involved in oncogenesis processes. Proteins were selected using the PharmMapper in-house pharmacophore model database. The results are presented in the article

Phosphorylation of Hyaluronic Acid

Chemical phosphorylation of hyaluronic acid (HA) remains an unresolved problem for the chemistry of this unique polysaccharide, since convenient phosphorylating reagents are not reactive enough to obtain HA phosphates (HA-P) with a satisfactory degree of esterification of hydroxyl groups. The synthesis of phosphates of low-molecular-weight (43 kDa) and high-molecular-weight (0.5–0.7 MDa) HA was undertaken using such reagents as sodium trimetaphosphate Na3P3O9, H3PO4, NaH2PO4/Na2HPO4, and anhydride P2O5. Solid-phase HA esterification with P2O5 was found to be the most convenient and efficient method. The HA-P samples were characterized by XRF and NMR spectroscopy (31P and 1H-31P) and contained, depending on the HA/P2O5 ratio, 0.30–6.25% P wt., in the form of disubstituted mono-, di-, and polyphosphates