Nucleophilic Centers Research Articles

Origin of the α‐Effect in SN2 Reactions

AbstractThe α‐effect is a term used to explain the dramatically enhanced reactivity of α‐nucleophiles (R−Y−X:−) compared to their parent normal nucleophile (R−X:−) by deviating from the classical Brønsted‐type reactivity‐basicity relationship. The exact origin of this effect is, however, still heavily under debate. In this work, we have quantum chemically analyzed the α‐effect of a set of anionic nucleophiles, including O‐, N‐ and S‐based normal and α‐nucleophiles, participating in an SN2 reaction with ethyl chloride using relativistic density functional theory at ZORA‐OLYP/QZ4P. Our activation strain and Kohn–Sham molecular orbital analyses identified two criteria an α‐nucleophile needs to fulfill in order to show α‐effect: (i) a small HOMO lobe on the nucleophilic center, pointing towards the substrate, to reduce the repulsive occupied–occupied orbital overlap and hence (steric) Pauli repulsion with the substrate; and (ii) a sufficiently high energy HOMO to overcome the loss of favorable HOMO–LUMO orbital overlap with the substrate, as a consequence of the first criterion, by reducing the HOMO–LUMO orbital energy gap. If one of these two criteria is not fulfilled, one can expect no α‐effect or inverse α‐effect.

Origin of the α-Effect in SN 2 Reactions.

The α‐effect is a term used to explain the dramatically enhanced reactivity of α‐nucleophiles (R−Y−X:−) compared to their parent normal nucleophile (R−X:−) by deviating from the classical Brønsted‐type reactivity‐basicity relationship. The exact origin of this effect is, however, still heavily under debate. In this work, we have quantum chemically analyzed the α‐effect of a set of anionic nucleophiles, including O‐, N‐ and S‐based normal and α‐nucleophiles, participating in an SN2 reaction with ethyl chloride using relativistic density functional theory at ZORA‐OLYP/QZ4P. Our activation strain and Kohn–Sham molecular orbital analyses identified two criteria an α‐nucleophile needs to fulfill in order to show α‐effect: (i) a small HOMO lobe on the nucleophilic center, pointing towards the substrate, to reduce the repulsive occupied–occupied orbital overlap and hence (steric) Pauli repulsion with the substrate; and (ii) a sufficiently high energy HOMO to overcome the loss of favorable HOMO–LUMO orbital overlap with the substrate, as a consequence of the first criterion, by reducing the HOMO–LUMO orbital energy gap. If one of these two criteria is not fulfilled, one can expect no α‐effect or inverse α‐effect.

Inside Back Cover: Origin of the α‐Effect in SN2 Reactions (Angew. Chem. Int. Ed. 38/2021)

The α-effect is a “reactivity booster” that affords the less basic peroxide (HOO−) the edge over hydroxide (HO−) in the Grand Prix of SN2 Reactivity. In their Research Article on page 20840, Trevor A. Hamlin and co-workers equip researchers with two criteria that α-nucleophiles need to fulfill to exhibit an α-effect: (i) a small HOMO lobe on the nucleophilic center, to reduce the destabilizing Pauli repulsion with the substrate; and (ii) a high-energy HOMO to overcome the loss of favorable orbital overlap with the substrate.

STUDY OF THE INTERACTION BETWEEN OXICAM DERIVATIVES AND COX1 USING FINGERPRINT DESCRIPTORS AND MOLECULAR DOCKING

Oxicam derivatives play an important role in the treatment of pain and inflammation. The mechanism of action of these compounds consists in the inhibition of cyclooxygenase (COX) and the blockade of isoform 1 of this enzyme (COX-1) is considered to generate adverse effects. The aim of this paper is to establish which of the atoms in the oxicams molecules are responsible for their inhibitory activities, using electronegativity as fingerprint descriptor. Using this descriptor and molecular docking programs, the atoms in the molecule that have a greater contribution to COX-1 inhibition have been identified. In the case of the studied molecules, the oxygen atoms and the nitrogen atoms are highlighted. The oxygen atoms participate in the interaction as electron acceptors through U-MO molecular levels (74.1%) and the nitrogen atoms participate in the interaction both as a nucleophilic center through the molecular state of HOMO (13.7%) and as an electrophilic center through the molecular state of LUMO (13.2%). In the case of three out of four of the studied compounds, the 4-hydroxyl group of the thiazine ring participates in the interaction with COX-1. The results are also supported by the 2D and 3Ddiagrams of the applied docking method.

ARYLTELLUROCHLORINATION OF N-ALLYLTHIOAMIDE OF TRIFLUOROACETIC ACID

Telluroganic compounds have a pronounced biological activity, namely, show antitumor, antioxidant, antiparasitic activity. The introduction of a trifluoromethyl group to such compounds can significantly increase the activity. Therefore, the aim of this study is the synthesis of tellurium-containing compounds by the electrophilic action of aryltellurium trichloride on N-allylthioamide of trifluoroacetic acid.
 As the object of the study of the aryltellurohalogenation process of N-allyl thioamide of trifluoroacetic acid was chosen. The selection is dictated by the presence of several nucleophilic centers suitable for the attack by electrophiles and can form both addition and cyclization products. The synthesis of the amide was performed through the interaction of ethyl ester of trifluoroacetic acid with allylamine in tetrahydrofuran followed by the treatment of the formed N-allylamide with phosphorus (V) sulfide in the presence of hexamethyldisiloxane in toluene.
 Propargyl trifluoroacetic acid amide was investigated in the halogenation reaction, which resulted in the addition product. It was important to establish the effect of the nature of the unsaturated alkenyl/alkynyl substituent, the additional nucleophilic center and the electrophilic reagent on the reaction pathway. The reaction of N-allyltrifluorothioacetamide with p-methoxyphenyltellurium trichloride was performed in chloroform or tetrahydrofuran at room temperature in equimolar amounts of reagents. The addition product N-(2-chloro-3- (dichloro (4-methoxyphenyl) -)-l4-4-tellanyl)propyl] -2,2,2-trifluoroethanethioamide was obtained. Similar addition products were formed in the reaction of N-allyl thioureas with aryltellurium trihalides.

SYNTHESIS AND BROMINATION OF 2-METALLYLTHIO-3-HYDROXYIMINOMETHYLQUINOLINE

Quinoline and its condensed analogues are an important class of heterocycles with a wide range of biological activity. Many quinoline derivatives are used as substrates in organic synthesis and molecular design of pharmacologically active substances with different effects. Its reported a number of natural compounds containing a quinoline fragment are used as drugs. The annulation of azole and azine heterocycles to the quinoline backbone expands the search for biologically active compounds in this series. The most convenient and most effective method of annulation of additional cycles to quinoline is the reaction of electrophilic intramolecular cyclization of its unsaturated derivatives with various electrophilic reagents. Therefore, the synthesis of previously unknown polycyclic quinoline derivatives is an urgent problem.
 The purpose of this work is to study of the regio-selectivity of the process of electrophilic intramolecular cyclization of 2-methallylthio-3-(hydroxyiminomethyl)quinoline.
 The model oxime was obtained by the condensation reaction of 3-formyl-2-methalylthioquinoline with hydroxylamine hydrochloride in an alcohol-alkaline medium. 2-Methallylthio-3-(hydroxyiminomethyl)quinoline has several nucleophilic centers for studying of the regioselectivity of electrophilic heterocyclization - a multiple bond of a methallyl fragment, an endocyclic nitrogen atom of quinolone cycle, an exocyclic nitrogen atom of an imino group and an exocyclic atom oxygen of ОН- group. During the bromination of such an oxime, the formations of both a linear and angular tricyclic system are possible. It was found that when brominated with a double excess of bromine in chloroform medium, the thiazole cycle is annealed to the quinoline backbone to form 1-bromomethyl-4-((hydroxyimino)methyl)-1-methyl-1,2-dihydrothiazolo[3,2-a]-quinolin-10-ium tribromide.
 Thus, as a result of the performed research, the 2-methallylthio-3-(hydroxyiminomethyl) quinoline was obtained and its bromination was carried out. It is proved that the bromocyclization of the model oxime occurs regio-selectively with the formation of angular tribromide of 1-bromomethyl-4 -((hydroxyimino)methyl) -1-methyl-1,2-dihydrothiazolo [3,2-a] quinolin-10-ium. This tricyclic salt has the potential to have high biological activity.

Coumarin‐Pyronin Hybrid Dyes: Synthesis, Fluorescence Properties and Theoretical Calculations**

AbstractA novel class of rosamine dyes bearing a 7‐substituted 4‐hydroxycoumarin unit as meso‐heteroaryl ring is presented. The latent C‐nucleophilic character of 4‐hydroxycoumarin derivatives (i. e., their C‐3 position as a nucleophilic center) has been drawn on in the design of two unprecedented synthetic routes towards these atypical xanthene dyes. The syntheses are based on an effective formal Knoevenagel condensation with either pyronin derivatives or a mixed bis‐aryl ether bearing both an aldehyde and a masked phenylogous amine, possibly applicable to a wide range of latent cyclic C‐nucleophiles. We also report experimental and theoretical photophysical investigations of these unique coumarin‐pyronin hybrid structures and particularly they form low‐lying quenching states, some dark and demonstrating a twisted intramolecular charge transfer (TICT) nature, depending on the medium (CHCl3 and water). Furthermore, two fluorophore compounds have been applied for imaging in paraformaldehyde‐fixed A549 cells to gain insights into their permeation and localization.

Exploration of interaction behavior between spiro[indene-2,2'-[1,3,5]oxathiazine]-1,3-diones and DNA with the help of DFT, molecular docking, and MD simulations

A detailed computational study covering density functional theory (DFT), molecular docking, and molecular dynamics (MD) simulations of some spirocyclic compounds interacting with a B-DNA has been performed. DFT calculations were performed using the B3LYP functional with 6-311++G(d,p) basis set and were used to identify the electrophilic and nucleophilic centers in electrostatic forces. NMR results were in agreement with previous experimental data and approved the reliability of the used method and basis set. The in silico screening results showed that spirocyclic compounds fulfill the Lipinski's rule of five and can be developed as potential oral bioavailable drug candidates. Based on molecular docking results, the binding affinities follow the 4c < 4d < 4a = 4b < 4e < 4g < 4f order and ranged from −8.6 to −9.7 kcal/mol indicating a reasonably favorable interaction between DNA and investigated compounds. The adducts were stabilized by hydrophobic and hydrogen bonding interactions. The MD simulations performed for 100 ns and the results are reported in terms of variables such as root-mean-square deviation (RMSD), root-mean-square fluctuation (RMSF), center of mass (COM) separation distance between DNA and ligands, intermolecular hydrogen bonds, and radial distribution functions (RDF). The MD simulations demonstrated that compounds 4a and 4d bind into the minor groove of 1BNA and may act as potential biological probes for B-DNA. Communicated by Ramaswamy H. Sarma

Selective Bromocyclization of 5-Amino-4-Alkenyl-1,2,4-Triazole-3-Thione

Here, we present a study on the regioselectivity cyclization of 5-amino-4-alkenyl-1,2,4-triazole-3-thiones. The presence of various nucleophilic centers causes the possibility of cyclization of an alkenyl fragment on different heteroatoms and the formation of a few alternative structures. Elemental bromine was utilized as an electrophilic agent, and two 6-(bromomethyl)-6-R-5,6-dihydro[1,3]thiazolo[2,3-c][1,2,4]triazol-3-amine hydrobromide salts were obtained as the only products when taking reaction in chloroform, acetic acid, or acetonitrile. The 1H and 13C APT NMR spectra analysis proved the formation of the 1,3-thiazolinium ring upon cyclization reaction. DFT calculations at the ωB97X-D3/6-311G(d,p) level of theory were utilized to analyze molecular electrostatic potential, electron localization function, and Hirshfeld atomic partial charges the intermediate bromonium cation. These theoretical calculations explain the experimentally observed regioselectivity.

Trifunctional Metal-Organic Framework Catalyst for CO2 Conversion into Cyclic Carbonates.

Herein, we reported a facile strategy for the preparation of trifunctional ionic metal-organic frameworks (MOFs) incorporating imidazolium cation functionalities. This strategy exploits the Debus-Radziszewski reaction to create the cationic imidazole ring by postsynthetic modification, meanwhile introducing exchangeable counteranions. On the basis of this strategy, MIL-101-IMOH-Br- has been synthesized, which combines Lewis acidic sites, Brønsted acidic sites, and nucleophilic centers to achieve catalysis for the carbon dioxide-epoxide cycloaddition into cyclocarbonate without any cocatalyst and solvent.

Corrosion Inhibitive Potentials of some 2H-1-benzopyran-2-one Derivatives- DFT Calculations

There is an increased demand for metals and alloys because of their use in household appliances and industrial machines. However, they react with the environment and are consequently prone to loss of strength and durability owing to corrosion. In a bid to eradicate or control this, the use of corrosion inhibitors has been employed. Quantum chemical calculations have been used to predict the corrosion inhibitive potentials of novel molecules and probe into their metals' surface mode of action. Density functional theory was employed here with a polar basis set, 6-31G(d), to investigate the corrosion inhibitive potentials of some 2H-1- benzopyran-2-ones derivatives via their electronic properties, global reactivity descriptors, electrostatic potential maps, and Fukui indices. The energy gaps follow the order: c &gt; e &gt; a &gt; d &gt; b &gt; g &gt; f &gt; h, indicative that compounds f and h would effectively protect metals’ surface against corrosion with the HOMO map essentially delocalized over the benzopyran-2-one moiety and the attached substituents while the LUMO plot shows a delocalization of the lowest vacant molecular orbitals over the entire benzopyran-2-one moiety. The asymmetric charge distribution on the inhibitors from the electrostatic potential maps indicates that each compound possesses reactive adsorption sites for bonding and back-bonding with the metal surface. The Mulliken charge distribution and the Fukui indices reveal that the adsorption of an inhibitor on a metal surface is not only via the heteroatoms like O, Cl, Br, and N. The contribution of carbon atoms as nucleophilic and electrophilic centers ensures effective interaction between a metal surface and the inhibitor and isolates the material from corroding environment.

Ultrasound-based synthesis, SC-XRD, NMR, DFT, HSA of new Schiff bases derived from 2-aminopyridine: Experimental and theoretical studies

The present work is related to the rapid and efficient preparation of Schiff bases (1 and 2) by reaction of 2-aminopyridine derivatives with 3-ethoxysalicylaldehyde under ultrasonic irradiation. The advantages, of using ultrasonic irradiation, are short reaction time, high yield and the ability to carry out large scale reactions. After characterization by NMR spectroscopic technique and elemental analyses, the crystal structures of compounds were confirmed by single crystal X-ray analysis (SC-XRD). For further elaboration of non-covalent interactions in the stabilization of packing of molecules, Hirshfeld surface (HS) inspection was accomplished by using crystal explorer software. B3LYP/Def2-TZVP level of theory was used to calculate electronic and structural parameters of synthesized compounds. Optimized structures and calculated data showed good correlation with experimental ones. In addition, two models of keto and phenol tautomerism were studied by calculating thermodynamic parameters and molecular electrostatic potential. Results showed that there are both nucleophilic and electrophilic centers in keto form, while only nucleophilic center is present in phenol form.

Degradation of Organophosphates Promoted by 1,2,4-Triazole Anion: Exploring Scaffolds for Efficient Catalytic Systems.

Organophosphate (OP) pesticides are responsible for numerous human deaths every year. Nucleophilic substitution is an important method to mitigate the toxicity of obsolete stocks of OPs. Herein, the degradation of O,O-diethyl-2,4-dinitrophenyl phosphate (DEDNPP) and pesticide diethyl-4-nitrophenyl phosphate (Paraoxon) promoted by 1,2,4-triazole (TAZ) was investigated by means of kinetic studies, nuclear magnetic resonance (NMR) analyses, and theoretical calculations. Results showed fast degradation of OPs is promoted by the anionic form of the nucleophile (TAZ(-)) in pH > 8.5 (optimal at pH = 11). Rate enhancements of 106 and 105-fold in relation to neutral hydrolysis of DEDNPP and Paraoxon were observed, respectively, consistent with alpha-nucleophiles reactivity. TAZ(-) regioselectively promotes the degradation of DEDNPP via P-O bond break, forming a quickly hydrolyzable phosphorylated intermediate, regenerating the nucleophile. Calculations using M06-2X/6-311++G(d,p) level of theory revealed that the equivalent nitrogen atoms of TAZ(-) are the main nucleophilic center of the molecule. This study expands the knowledge on the reactivity of iminic compounds as detoxificant agents of OPs, indicating the efficiency and selectivity of TAZ(-) in aqueous medium, encouraging the design of novel TAZ-based catalysts.

MOF@POP core–shell architecture as synergetic catalyst for high-efficient CO2 fixation without cocatalyst under mild conditions

A bifunctional MOF@POP core-shell catalyst (NH2-UiO-66(Hf)@CoTPy-CAP) constructed by amino functionalized NH2-UiO-66(Hf) and ionic porphyrin-based CoTPy-CAP was first reported to be applied in the cycloaddition of CO2. Because NH2-UiO-66(Hf)@CoTPy-CAP both possess abundant Lewis acidic sites and nucleophilic centers in one system, the catalyst can efficiently catalyze CO2 fixation with epoxides without homogeneous cocalyst under mild conditions, achieving propylene oxide (PO) conversion of 98 % at 80 °C and 0.5 MPa. Furthermore, the bifunctional synergetic catalyst was easy to be recovered and recycled for five runs, and the reduction of activity was not obvious. This present work provides a viable direction for the fabrication of bifunctional synergetic catalysts for high-efficient CO2 fixation without cocatalyst under mild conditions.

First Principle Analysis on Pyridine Amide Derivatives’ Adsorption Behavior on the Pt (111) Surface

The reactivity and adsorption behavior of three pyridine amide additives (Nicotinamide, Pyridine-2-formamide and Pyridine-4-formamide) on the Pt (111) surface was studied by First principle methods. The quantum chemical calculations of molecular reactivity show that the frontier orbitals of the three additives are distributed around the pyridine ring, oxygen atom of carbonyl and nitrogen atom of amino, and the nucleophilic and electrophilic active centers are located on the nitrogen atoms of pyridine ring, oxygen atom of carbonyl and nitrogen atom of amino. All three molecules were adsorbed with the chemical adsorption on the Pt (111) surface, and the order of adsorption was Nicotinamide &gt; Pyridine-2-formamide &gt; Pyridine-4-formamide. The C and N atoms of three derivatives forms C-Pt and N-Pt bonds with the Pt atoms of the Pt (111) surface, which makes derivatives stably adsorb on the Pt surface and form a protective film. The protective film inhibits the diffusion of atoms to the surface of the growth center, so as to inhibit the formation of dendrite and obtain a smooth aluminum deposition layer.

Conformational Stability, FMO, NMR, MEP and NBO Analysis of 2,5-Di-methyl-2,5-bis(methylthio)-1,4-dithiane and Dimethoxy compounds by DFT Approach

Abstract: Conformational behaviors of 2,5-dimethoxy-2,5-dimethyl-1,4-dithiane (compound 1) and 2,5-dimethyl-2,5-bis (methylthio)-1,4-dithiane (compound 2) investigated by computational methods including B3LYP/6-311+G** and M06-2X/6-311+G** levels of theory and NBO analysis. The stereoelectronic effect of axial, axial (ax, ax) and equatorial, equa-torial (eq, eq) conformations were studied using NBO analysis. Using NBO analysis, the values of the stereoelectronic effects were calculated through the energy of stability associated with the electron transfers of compounds 1 and 2. The results showed that the eq, eq conformations of the studied compounds were more stable than their corresponding ax, ax conformations, and LP2X→σS1-C2 and LP2S→σ*C2-X electron transfers play important roles in the conformational be-havior of the studied compounds. The main purpose of the present work was to study the effects of stereoelectronic inter-actions and steric on the conformational superiority of the di-methoxy (compound 1) and di-thiomethyl compounds (com-pound 2). Thus, the values of resonance stability energy, non-diagonal elements, and orbital populations were investigated. Also, active electrophilic and nucleophilic centers were identified using fronting orbitals analysis obtained by DFT methods. The electrostatic potential maps of the title compounds were investigated at the B3LYP/6-311+G* level of theory. All of the NMR parameters and geometrical properties of both compounds were determined in this study.

Understanding the different reactivity of (Z)- and (E)-β-nitrostyrenes in [3+2] cycloaddition reactions. An MEDT study.

The experimental reactivity of isomeric (Z)- and (E)-β-nitrostyrenes participating in [3+2] cycloaddition (32CA) reactions has been analysed on the basis of molecular electron density theory (MEDT) at the HF/6-311G(d,p), B3LYP/6-311G(d,p) and ωB97X-D/6-311G(d,p) computational levels. It was found that the polar zw-type 32CA reactions with 5,5-dimethylpyrroline-N-oxide proceed via a one-step mechanism, characterised by the attack of the nucleophilic oxygen centre of the nitrone on the electrophilically activated β-position of these nitrostyrenes. This behaviour is completely understood by means of the analysis of the conceptual DFT reactivity indices. These 32CA reactions present low activation enthalpies of 4.4 (Z) and 5.0 (E) kcal mol−1, and are exo (Z) and endo (E) stereoselective (B3LYP), as well as completely meta regioselective (ωB97X-D, B3LYP). The less stable (Z)-β-nitrostyrene is more reactive than the (E)-one (HF). ELF and AIM topological analyses of the reagents and TSs show the great similitude between their electronic structures. Finally, NCI allows explaining the exo stereoselectivity found in the reaction of (Z)-β-nitrostyrene. The present MEDT study explains the different reactivity, selectivity and competitiveness in the title reactions.

SYNTHESIS AND BROMINATION OF PROPARGYLIC TRIFLUOROUTIC ACID AMIDE

Carboxylic acid amides are convenient reagents for organic synthesis, and are promising building blocks for obtaining a large number of acyclic and heterocyclic compounds.Among the various aliphatic, aromatic and heterocyclic amides, fluorine-containing derivatives are the least studied. The presence of a carbonyl group, a fluoroalkyl substituent and an alkyl-substituted amino functional groups determines the variety of transformations for this class of compounds. The introduction of an unsaturated alkyl substituent to the amide nitrogen atom and the presence of an additional nucleophilic center of the oxygen or nitrogen atom makes such amides promising for the study of their reactions with electrophilic reagents.The aim of this work is the synthesis of propargyl trifluoroacetic acid amide and the study of its interaction with bromine.Trifluoroacetic acid propargylamide was prepared from trifluoroacetic acid ethyl ester and propargylamine in tetrahydrofuran medium, its structure was confirmed by NMR1H and NMR19F spectra.It is known from the literature sources that the presence of a multiple bond and an additional intramolecular nucleophilic center in propargyl amines and amides creates the pre-conditions for the cyclization reaction under the action of halogen-containing electrophilic reagents. Such structural features are also characteristic for N-propargyltrifluoroacetamide, namely the multiple bond of the propargyl moiety and additional intramolecular nucleophilic centers of nitrogen and oxygen atoms. Under the action of bromine as an electrophilic reagent on N-propargyltrifluoroacetamide, the formation of both the coupling product and the cyclization with the formation of azetidine, oxazoline or oxazine heterocycles is possible.The bromination reaction of N-propargyltrifluoroacetamide was performed in dichloromethane with an equimolar amount of reagents in the presence of potash. According to the spectral data, the coupling product N- (2,3-dibromoprop-2-en-1-yl) trifluoroacetamide is formed, which is confirmed by the NMR1H and NMR19F spectra. The absence of the cyclization process can be explained via the lower nucleophilicity of the oxygen atom compared to sulfur.

REGIOSELECTIVITY OF ALKYLATION REACTION OF 2-OXO-(THIO)-3-PHENYL-THIENO[2,3-d]PYRIMIDINONES

The elaboration of easy and affordable highly selective methods for the synthesis of thieno[2,3-d]pyrimidine derivatives, which operate on none toxic reagents and energy-saving techniques, is an urgent task of organic chemistry. Among the large number of functional derivatives of the title heterocycle, the most interesting objects for our research group are 2-oxo-(thio)-3-phenyl-thieno[2,3-d]pyrimidinones, which contain several reactive nucleophilic centers (nitrogen, oxygen and sulfur atoms), which determines their ambidenties in reactions with electrophilic reagents. Many approaches to the introduction of substituents and functional groups into the thieno[2,3-d]pyrimidine system have been developed, among which the alkylation reactions are the most common. In our previous study, we theoretically predicted the regioselectivity of the alkylation of 2-oxo(thioxo)-3-phenyl-thieno[2,3-d]pyrimidin-4-ones and investigated possible influencing factors.In continuation of this study, in order to reliably validate the results of previous computer simulations, we alkylated the title heterocyclic system with a number of alkylating reagents under the same synthetic conditions, which involve the alkylation of the most thermodynamically advantageous anionic form. 2-Oxo-(thio-)-3-phenyl-5,6,7,8-tetrahydro[1]benzothieno[2,3-d]pyrimidinones were used as starting compounds. To provide alkylation conditions for the most thermodynamically advantageous anion, the starting compounds were heated with excess of potassium hydroxide in ethanol until completely dissolving. The resulting solution of the corresponding potassium salts was cooled and kept at room temperature, after which an excess of alkylating reagent was added and kept at room temperature an additional time.As a result of research, a preparative method of alkylation of 2-oxo-(thio-)-3-phenyl-5,6,7,8-tetrahydro[1]benzothieno [2,3-d] pyrimidinones was developed, which corresponds to the principles of green chemistry (operates with none toxic solvents, easy to perform and does not require long-term heating). The sixteen new previously undescribed thieno[2,3-d]pyrimidine derivatives were obtained.

Reactivity of bulky aminophosphanes towards small molecules: Activation of dihydrogen and carbon dioxide by aminophosphane/borane frustrated Lewis pairs

A series of mono- and bisaminophosphanes with formulas R2NPR’R’’ and (R2N)2PR’ (R = iPr, Cy; R’ = Ph, Cy; R’’ = iPr) were characterized by X-ray analysis, NMR spectroscopy and computational methods. The common structural futures of these species are short and polarized PN bonds, a pyramidal geometry at the P atom and an almost planar geometry at the N atoms. According to DFT calculations, these compounds are highly nucleophilic, with nucleophilic centers located on the N and P atoms. Except for species containing a PPh2 moiety, the obtained aminophosphanes are air-stable and do not react with water. They form stable frustrated Lewis pairs with BPh3 or B(C6F5)3. Mono- and bisaminophosphanes in the presence of B(C6F5)3 activate dihydrogen and carbon dioxide at room temperature.