Interaction between (tert-butoxysilyl)methylmagnesium chlorides of the general formula Me3-n(t-BuO)(n)SiCH2MgCl, n = 1-3, with some organotin and organosilicon monochlorides has been studied. It has been found that the reaction of the Grignard reagents with trialkyltin chlorides readily proceeds via the methylene carbon with the formation of C-substituted products Me3-n(t-BuO)(n)SiCH2SnR3, R = Me, n-Bu in high yields. The path of this reaction with Me3SiCl and MePh2SiCl depends on the structure of Grignard compound and chlorosilane electrophilicity. Increasing the number of the tert-butoxy groups in the Grignard reagent has unexpectedly been found to result in the formation of Me3-n(t-BuO)(n)SiCH2OSiMeR2, R = Me, Ph and decrease of the organosilylmethyl silicon compounds content in the reaction products. The structure of the compounds synthesized has been confirmed by H-1, C-13, Si-29, Sn-117,Sn-119 NMR spectroscopy and mass spectrometry.

Derivatization of the natural flavonoid dihydroquercetin with p-aminobenzoic acid was carried out in an ethyl acetate/citric buffer biphasic system using laccase from the fungus Trametes hirsuta. The main reaction product yield was ~68 mol %. The product was characterized by 1H NMR, 13C NMR, and liquid chromatography-mass spectroscopy, and its structure was elucidated. The reaction product affected viability of cultured human rhabdomyosarcoma cells (RD cell line) in a dose-dependent manner and, therefore, can be of interest to pharmaceutical industry.

Multicopper oxidases such as bilirubin oxidase (BOD) from Myrothecium verrucaria and laccase (LC) from the basidial fungus Trametes hirsuta have been used as catalysts in dihydroquercetin (DHQ) oxidative polymerization. The conditions selected enabled good yields of DHQ oligomers, which were then analyzed using UV-vis, FTIR, 1Н and 13С NMR spectroscopy. DHQ oligomers synthesized using both enzymes showed higher thermostability as compared with the monomer. Depending on the oxidase, the products of DHQ polymerization differed in physicochemical properties, and as shown by NMR studies, had different structures.

Organosiloxyalumoxane and organoalumoxanesiloxane oligomers were synthesized 30 years 9 ago [1]. Their probable structure from conventional viewpoint looked like three-coordinated Al atom. 10 These compounds are amorphous, therefore it did not seem possible to prove their structure by 11 means of X-ray diffraction. But in the middle of 1980s papers dealing with nonclassical structure of 12 alumoxane and alumosiloxane compounds with four-coordinated Al atom and three-coordinated 13 oxygen atom were published [2–4]. The coordination number of Al atoms in bicyclic and oligomer 14 alumoxanes and alumosiloxanes was shown to be 4 and may increase to 5 (or even to 6) [2]. The 15 crystalline structure of alumosiloxane of C8H24Al3Br5O6Si4 composition was proved [5]. It was found 16 that the molecule of crystalline alumosiloxane consisted of four condensed nuclei: two planar four17 membered rings, built from two aluminum atoms and two oxygen atoms, and two "saddle-shaped" 18 six-membered rings composed of alternating silicon, oxygen, and aluminum atoms. The Al atom, 19 which belongs to all four rings, has a coordination number of 5. The remaining atoms of aluminum 20 and silicon have tetrahedral coordination. 21 Based on the data of [2–5], the results of [1] were analyzed. In addition, the reaction of Al(iBu)3 22 with Ph2Si(OH)2 in hexadeuterobenzene was studied. The results obtained suggested a probable 23 scheme for the interaction of Al(iBu)3 with Ph2Si(OH)2 and the possible structure of the oligomers 24 obtained [6]. However these results were not published. 25 Since the beginning of the 1990s, detailed studies of the synthesis, properties, and structure of 26 alkylalumoxanes have been carried out [7–14]. In 2013, works on this problem were summarized in 27 the review [15]. 28 The nearest aspect of our work was the investigation performed by Andrew R. Barron's group, 29 they studied the synthesis, properties and structure of organosiloxyalumoxanes precursors of 30 alumosilicate ceramics [16,17]. 31 A considerable number of molecular alumosiloxanes and alumosilicates have been obtained 32 using aluminum halogenides, chalcogenides, hydrides, and organometallic compounds as starting 33 materials, by reacting them with the appropriate RnSi(OH)4-n precursor [18].The reaction of Al2Cl6 34 with an excess of Ph2Si(OH)2 in THF in the presence of pyridine yielded new anionic and cyclic 35 aluminosiloxanes: the structure of the anionic complex comprises separated pyridinium cations and 36 alumosiloxane anions with a tetrahedral arrangement around the Al atom, which is similar to that in 37 natural aluminosilicates; the core of the cyclic aluminosiloxane is a twelve-membered Al2Si4O6 ring 38 in a chair conformation, which contains a Cl group on each of the two Al atoms [19]. Reaction of 39 Al(tBu)3 with neol-H2 (2,2-dimethylpropane-1,3-diol) yields [Al2(tBu)4(neol-H)2]. [Al2(tBu)4(neol-H)2] 40 may be considered as bifunctional (two OH groups), tetradentate (4O) ligands as highlighted by its 41 reactivity with Group 13 hydrides and alkyls. Reaction of [Al2(tBu)4(neol-H)2] with AlH3(NMe3), 42 AlH2Cl(NMe3) and AlMe3 yields the tri-aluminium compounds, [Al3(tBu)4(X)(neol)2] with X = H, Cl, 43 Me, respectively [20]. 44 The main research on the synthetic and structural chemistry of alumosiloxanes is described in 45 the review [21]. Michael Veith's works describe the synthesis, physicochemical properties, crystal 46 structure and interaction of polycyclic [Ph2SiO]8[AlO(OH)]4 with various chemical compounds [22– 47 25]. 48 Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 28 September 2017 doi:10.20944/preprints201709.0144.v1

Дигидрокверцетин (или таксифолин) - один из важнейших представителей флавоноидов, в большом количестве присутствует в лиственнице сибирской. Исследована окислительная полимеризация дигидрокверцетина (ДГК) с участием билирубиноксидазы (БОД) в качестве биокатализатора и изучены некоторые физико-химические свойства полученных продуктов. При оптимальных условиях синтеза в результате ферментативной реакции образуются олигомеры ДГК (олигоДГК) с мол. массой 2800 и индексом полидисперсности 8,6. ОлигоДГК растворимы в диметилсульфоксиде (ДМСО), диметилформамиде (ДМФА) и метаноле. УФ-видимые спектры олигоДГК в ДМСО указывают на наличие системы сопряженных связей. Синтезированные олигоДГК были охарактеризованы методами ЯМР и ИК-спектроскопии. Сравнение спектров ЯМР олигоДГК с мономером и родственными флавоноидами показало, что полимер имеет нерегулярную структуру, образующуюся в результате ферментативного окисления ДГК с последующей неселективной радикальной полимеризацией. По сравнению с мономером олигоДГК имеют более высокую термостабильность и обладают высокой антиоксидантной активностью.

Dihydroquercetin (or taxifolin) is one of the most famous flavonoids and is abundant in Siberian larch (Larix sibirica). The oxidative polymerization of dihydroquercetin (DHQ) using bilirubin oxidase as a biocatalyst was investigated and some physicochemical properties of the products were studied. DHQ oligomers (oligoDHQ) with molecular mass of 2800 and polydispersity of 8.6 were obtained by enzymatic reaction under optimal conditions. The oligomers appeared to be soluble in dimethylsulfoxide, dimethylformamide, and methanol. UV-visible spectra of oligoDHQ in dimethylsulfoxide indicated the presence of highly conjugated bonds. The synthesized oligoDHQ was also characterized by FTIR and (1)H and (13)C NMR spectroscopy. Comparison of NMR spectra of oligoDHQ with DHQ monomer and the parent flavonoids revealed irregular structure of a polymer formed via the enzymatic oxidation of DHQ followed by nonselective radical polymerization. As compared with the monomer, oligoDHQ demonstrated higher thermal stability and high antioxidant activity.

Benchmark calculations of geminal and vicinal 29Si–1H spin–spin coupling constants across double bond in three reference alkenylsilanes have been carried out at both DFT and SOPPA levels in comparison with experiment. At the former, four density functionals, B3LYP, B3PW91, PBE0 and KT3, were tested in combination with five representative basis sets. At the latter, three main SOPPA‐based methods, SOPPA, SOPPA(CC2) and SOPPA(CCSD), were examined in combination with the same series of basis sets. On the whole, the wavefunction methods showed much better results as compared to DFT, with the most efficient combination of SOPPA/cc‐pVTZ‐su2 characterized by a mean absolute error of only 0.4 Hz calculated for a set of nine coupling constants in three compounds with a sample span of around 40 Hz. Copyright © 2012 John Wiley & Sons, Ltd.

The calculations of geminal and vicinal 29Si–1H spin–spin coupling constants across double bond in 15 alkenylmethylsilanes and alkenylchlorosilanes were carried out at the second‐order polarization propagator approach level in a good agreement with experiment. Two structural trends, namely, (i) the geometry of the coupling pathway and (ii) the effect of the electrowithdrawing substituent, have been interpreted in terms of the natural J‐coupling analysis within the framework of the natural bond orbital approach. Thus, the marked difference between cisoidal and transoidal 29Si–1H spin–spin coupling constants across double bond was accounted for the delocalization contributions including bonding and antibonding Si–C and C–H orbitals, whereas the chlorine effect was explained in terms of the steric contributions including bonding Si–Cl orbitals. Copyright © 2012 John Wiley & Sons, Ltd.

A series of new boron-containing carboxylic acids was prepared by the ring-opening reaction of cyclic oxonium derivatives of the closo-decaborate anion [B10H10]2− with methyl esters of hydroxybenzoic acids or the cyanide anion followed by hydrolysis of the obtained nitrile and esters. Acid hydrolysis of the esters results in protonation of the oxygen atom connected to the boron cage, with the formation of the corresponding O-protonated acids, isolated in the solid state. The compounds synthesized can be used in radionuclide diagnostics and boron neutron capture therapy of cancer.

New linear and branched oligodialkylalkylhydrosiloxanes were prepared by hydrolytic cocondensation of various functional organosilanes with diethyl(dimethyl-)dichlorosilane, ethylhydro-(methylhydro-) dichlorosilane, and trimethylchlorosilane, followed by catalytic rearrangement in the presence of an electrophilic catalyst. The products are of interest as hydrophobizing agents and starting compounds for replacement of hydrogen atoms at silicon by other substituents.

The behavior of palladium diacetate cyclic trimer [Pd(OAc)(2)](3) (1) upon its dissolution in methanol and wet chloroform was studied by (1)H and (13)C NMR including 2D-HSQC and 2D-DOSY techniques. Upon dissolution, trimer 1 reacts with methanol and is completely transformed first into the methoxo complex Pd(3)(μ-OMe)(OAc)(5) (2), which already at -18 °C undergoes a slow exchange of second bridging acetate ligand between the same palladium atoms to form the symmetric dimethoxo complex Pd(3)(μ-OMe)(2)(OAc)(4), the maximum relative concentration of which reaches 20-30 mol % of initial loading trimer 1. Along with the dimethoxo complex, both soluble and insoluble polynuclear palladium clusters are gradually formed at -18 °C, and their total amount reaches up to 60% of the starting Pd(2+) loading. The increase of temperature to 27 °C results in the reduction of palladium(II) to Pd metal by methanol, which is oxidized and transformed into formaldehyde hemiacetal and methyl formate. Upon dissolution in wet chloroform, trimer 1 is reversibly hydrolyzed to the hydroxo complex Pd(3)(μ-OH)(OAc)(5) (10) in ratio 1/10 ≈ 3/1. The temperature decrease and addition of acetic acid shift the equilibrium in this system toward trimer 1, and addition of water shifts it in the opposite direction. Addition of methanol to the equilibrium mixture of 1 and 10 results in the fast exchange of bridging acetate in trimer 1 by the μ-OMe group. Substitution of the μ-OH ligand by μ-OMe in 10 occurs in parallel but more slowly. Complex 2 formed in both cases is more stable in chloroform than in methanol.

Unsymmetrical 1,2-bis(diorganylsilyl)ethanes were synthesized by two procedures. Hydrosilylation of chloro(vinyl)silanes were used to obtain compounds of the general formula ClMe2SiCH2CH2SiRMeCl with different substituents (R = Et, Vin, Ph) on the silicon atom. Chlorodealkylation of 1,2-bis(trialkylsilyl)ethanes gave compounds of the general formula ClAlk2SiCH2CH2SiAlk2Cl (Alk = Me, Et, Pr). It is established that the latter reaction provides high yields only with Me-and Et-substituted compounds, whereas Pr-substituted products are formed in poor yields. The mechamism of this reaction based on quantum-chemical calculations is offered.

Investigation of the reaction of some vinylsilanes of the general formula Cl3−n (CH3) n SiCH=CH2 (n = 0,1,2,3) and 1,2-bis(trimethylsilyl)ethylene with trimethylgermane and trichlorogermane etherate was carried out. It was established that hydrogermylation only at the use of HGeCl3·2Et2O was sensitive to the nature of the substituting silyl groups in vinylsilanes. Nucleophilic mechanism of the reaction of trichlorogermane etherate with vinylsilanes is suggested.

By electrochemical iodination of potassium 7-methyl-7,8-dicarba-nido-undecaborate and potassium 7,8-dimethyl-7,8-dicarba-nido-undecaborate, their monoiodine derivatives (extracted as tetramethylammonium salts) are synthesized. Their structure is confirmed by NMR and IR spectra and also by elemental analysis data.

Hydrosilylation of cyclohexene and allyl chloride in the presence of Pt(0) complexes with tetramethyldivinyldisiloxane (Karstedt catalyst) and hexavinyldisiloxane was studied. It was shown that these catalysts are much more active in the hydrosilylation of cyclohexene with trichloro-, dichloro(methyl)-, and chlorodimethylsilane than the Pt(II)-containing Speier catalyst. In the hydrosilylation of allyl chloride in the presence of Pt(0) complexes, the ratio of the fraction of addition products to the fraction of reduction products increases from 5.7 (Speier catalyst) to 10–16. Quantum-chemical calculations showed that Pt(0) complexes are more active than Pt(II) complexes on the stage of formation of platinum silicon hydride complexes.