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Structure of six-membered cyclic aminoiminocarbenes (pyrimidine ylidenes) and their group 13–15 homologues was studied by quantum chemical calculations. Isodesmic and dimerization reaction energies, NICS values, frontier molecular orbitals, as well as NBO, Bader’s “atoms in molecules” and Laplacian bond order (LBO) analyses were employed for estimating relative stability of the studied carbenes (carbene homologues). They show a low degree of aromatic delocalization and considerable variation of electronic structure depending on the nature of divalent element. The predicted stability for the series of interest is lower than that for the corresponding five-membered Arduengo carbenic structures, but comparable with Alder’s bis(dimethylamino)carbene.

All three possible inherently chiral (cS)-propyloxy-octyloxy-calix[4]arene acetic acids were synthesized and their absolute configuration was proved. Complexation of the calix[4]arene acetic acids with a number of chiral compounds have been studied by molecular modeling and 1H NMR spectroscopy and enantioselectivity of binding of R- and S-forms of 2-aminobutanol was found.

Structure of 1,3,2-diazaphosphinine heterocyclic system was studied using quantum chemical calculations and X-ray diffraction method for one derivative. It was found that two P–N single bonds were different in their nature: one of them turned out to be significantly shorter and stronger, whereas the other one is longer and more diffused. The found effect is strengthened by π-donor substituents. The effect was interpreted by equilibrium of Lewis structures and analyzing the charge distribution by the NBO approach. The observed effect can be considered as the special form of π-conjugation in the heterocycles with the phosphorus (V) atom included.

We developed enhanced method for low temperature and good yield preparation of aryl and heteryl sulfur pentafluorides from chlorotetrafluorides using mercury oxide - hydrogen fluoride and mercury oxide - pyridinium poly(hydrogen fluoride) media as the fluorinating reagents.

All six possible stereoisomers of calix[4]arenes with four different substituents on the lower rim of the macrocycle have been synthesized by stepwise alkylation of the hydroxyl groups of tert-butylcalix[4]arene using (R)- or (S)-1-phenylethylamide groups as chiral auxiliaries. They form three enantiomeric pairs, as confirmed by the values of their specific rotation.

An approach to the synthesis of the novel cyclic sulfonimidoyl fluorides was elaborated based on the electrophilic fluorination of 1-oxo-2H-1,2,4-benzothiadizines with Selectfluor®. Crystal structure of 1-oxo-1-fluoro-3-phenyl-1,2,4-benzothiadiazine was determined.

Calixarenes substituted at the upper rim by electron-deficient pentafluorophenyl groups have been synthesized by reaction of hexafluorobenzene with organolithium derivatives of calixarenes. The single crystal structures indicate stacking interactions between the two perfluorinated aromatic rings. The thermodynamic characteristics of the flattened cone-flattened cone inversion process have been studied using dynamic NMR and quantum chemical methods. The calculated activation free energy for tetra(pentafluorophenyl)-substituted species is higher than that derived for tetraphenyl calixarene. The calixarenes substituted at the upper rim by electron-deficient pentafluorophenyl groups are potential hosts for anion recognition.

This article summarizes some of our investigations of compounds featuring the structural fragment P‒C‒P. Phosphorus atoms in different oxidation states and coordination numbers display different chemical behaviors. This may lead to unique chemical properties when they are bridged by a methylene group in a P‒CH2‒P system. For example, the PIII‒CH2‒PVunit is able to add different unsaturated compounds to give zwitterionic products with oppositely charged phosphorus atoms. In addition, the two hydrogen atoms in P‒CH2‒P may also take part in different transformations, resulting in the formation of carbodiphosphoranes or in the formation of a direct P-P bond to give three-membered ring diphosphiranes.

The reactions of 1,3-diphosphaphenalene 3 with sulfur, borane-tetrahydrofuran, and transition metal carbonyls are reported.

The salt (η5-pentamethylcyclopentadienyl)silicon(II) tetrakis(pentafluorophenyl)borate (5) reacts at −78 °C with lithium bis(trimethylsilyl)amide in dimethoxyethane (DME) as solvent to give quantitatively the compound [bis(trimethylsilyl)amino][pentamethylcyclopentadienyl]silicon(II) 6A in the form of a colorless viscous oil. The reaction performed at −40 °C leads to the silicon(IV) compound 7, the formal oxidative addition product of 6A with DME. Cycloaddition is observed in the reaction of 6A with 2,3-dimethylbutadiene to give the silicon(IV) compound 8. Upon attempts to crystallize 6A from organic solvents such as hexane, THF, or toluene, the deep yellow compound trans-1,2-bis[bis(trimethylsilyl)amino]-1,2-bis(pentamethylcyclopentadienyl)disilene (6B), the formal dimer of 6A, crystallizes from the colorless solution, but only after several days or even weeks. Upon attempts to dissolve the disilene 6B in the described organic solvents, a colorless solution is obtained after prolonged vigorous shaking or...

Isotropic C-13 nuclear magnetic shielding values (sigma(iso)) and corresponding chemical shift magnitudes (delta(C)) have been calculated for the large series of the thiocarbonyl compounds using DFT (RI-BP86 and B3LYP) and ab initio (RHF and MP2, with or without resolution of the identity approximation) levels of theory and different basis sets. As expected, the Hartree-Fock method and hybrid B3LYP approach essentially overestimate deshielding of the C=S carbon nuclei. The RI-BP86 level of approximation provides a noticeably better agreement with the experiment and can be used for calculations of the theoretical C-13 NMR spectra for the most classes of the thiocarbonyl compounds. Geometry optimizations and the nuclear magnetic shielding calculations using the MP2 level of theory provide the most reliable results. The resolution of the identity algorithm implemented into the TURBOMOLE program set does not affect the calculated sigma(iso) and delta C values compared to the strict MP2 nuclear magnetic shielding calculations (using the GAUSSIAN-03 program packet). A poor agreement with the experiment found in the case of the thiourea and thiosemicarbazide derivatives is referred to the different conformations of these species in the gas phase, solid state, and solution.

The reaction of potassium fluoride with the corresponding acid chlorides results in the formation of dialkylamido sulfoxylic acid fluorides Alk 2 N-S-F. Stereo- and regioselectivity of dimethylamido and diisopropylamido sulfoxylic acid fluorides addition reactions to the C,C double bond in cyclohexene, 3,4-dihydro-2H-pyrane, and vinyl ethyl ether has been investigated. This reaction is a convenient approach to the β -fluoroalkyl sulfenic acid derivatives.

The 1.4-diphospha-2-azol-5-ylidene is a homologue to the Ender's type carbene. It is a possible candidate for a ligand in the metathesis reaction of olefins. Based on density functional calculations the differences between the electronic structures of both systems are evaluated. The NHC (N-heterocyclic carbene) possesses a larger singlet-triplet energy separation than the PHC (P-heterocyclic carbene) analogue. Thus the latter exerts a larger Lewis acidity than the former. In comparison with, the donor-ability (a-basicity) in both systems is similar. As a consequence for the PHC carbene a Ru-fragment as a ligand for catalysis is stronger bound. This causes in the olefin metathesis a lower dissociation energy (compared to the NHC analogue) with respect to the formation of the catalyst active 14el species. As a consequence, the olefin will be weaker bound as well. This can be overcome by attaching sterically demanding substituents such as mesityl or super-mesityl to the phosphorus atoms. They induce mutual steric hindrance with concomitant increase of the S-T separation of the free carbene. Thus the Lewis acidity of the carbene is reduced. On this basis for the PHC's with larger S-T energy separations the dissociation energy of the phosphine fragment is raised and the adding olefin fragment will be stronger bound to the transition metal. While these effects describe the electronic situation in the reactive species, steric effects at the ligand carbene mediate the stabilities of the individual intermediates in the metathesis reaction by exertion of inter- and intra-ligand repulsion. (c) 2005 Elsevier B.V. All rights reserved.

A variety of conformations for three model calix[4]arenes with 8 or 12 OH groups have been investigated by calculations at density functional (RI-BP86) and RI-MP2 level of approximation. The calixarenes form stable complexes with the alkali metal cations of lithium up to caesium. For the investigations all-valence electron basis sets as well as various effective core potentials were probed. The stabilities of complexes were analysed in comparison with the corresponding benzene complexes, M(+)center dot C6H6. The formation of the calixarene metal complexes is considered in two steps, (a) in a distortion from the equilibrium conformation of the free calixarenes and (b) subsequent complexation. The distortion energies are small for the 'crown' and larger for the 'boat' conformations. On the other hand the latter are more stabilized by significant interaction energy of the cation with two adjacent pi-systems of the aromatic rings. As a result, these two conformations are of similar stabilities for K+ to Cs+ complexes with resorc[4]arenes, with a slight advantage for the 'boat' structure. The most stable conformation for the coordination products of these cations with the calix[4]arene with 12 OH groups is a slightly flattened 'crown' that is derived by maximum hydrogen bonding of the OH-groups and the most effective cation-pi interactions. Special cases are complexes of Li+ and Na+ which in most instances prefer the coordination on the oxygen atoms of the upper rim of the calixarene cavities and thus form 'boat'-like structures. (c) 2005 Published by Elsevier B.V.

Donor-acceptor interactions of Lewis bases, such as amine, phosphine, cyanic acid and phosphaalkine with various phosphinidene complexes carrying a W(CO)(5) fragment are studied by means of density functional calculations. Accordingly, the donor interactions can be divided into two categories. In terms of energy an amine binds stronger than a phosphine to a phosphinidene. the resulting Do-P bond is longer (N-P) or equal (P-P) with respect to a corresponding single bond, This tendency is also revealed in the corresponding transition metal complexes. In all cases the singlet-triplet energy separation values of the resulting donor-adducts are fairly small. A donor with a pi-system, such as HCN yields a shorter N-P bond, but the resulting donor-adduct is even less stable with respect to decomposition into a singlet PH complex and cyanic acid. Similar considerations with HCP reveal only a weak donor addition of this fragment to the parent PH complex but a facile rearrangement of the adduct to the diphosphirene transition metal complex. The diaminophosphino-PH possesses a singlet ground state, its corresponding transition metal complex reveals a fairly small singlet-triplet energy separation. It can be considered as a nucleophilic PH complex in contrast to the other homologues which reveal an electrophilic behaviour. (C) 2002 Published by Elsevier Science B.V.

An unusual P,P-disubstituted diphosphiranes was prepared and characterized by treatment of 1,8-bis[bis(di-alkylamino)phosphino]naphthalenes HCl followed by Me4NF.

The 2,3-diphospha- and 2-aza-3-phosphabuta- 1,3-dienes (H3Si)(2)C=P-X=CYY' (1 X= P, Y, Y' = NH2; 2 X = P, Y, Y' = H; 7 X = N, Y, Y' = NH2; 8 X = N, Y, Y' = H; 9 X = N, Y = NH2 (E-), Y' = H (Z-); 10 X = N, Y = H (E-), Y' = NH2 (Z-)) as well as the isostructural butadienes (H3Si)(2)C=CH-CH=CY2 (5 Y = NH2; 6 Y = H), the symmetrical diphosphabutadienes (H3Si)(2)C=P-P=C(SiH3), (3) and (H2N)(2)C=P-P=C(NH2)(2) (4), were explored with ab initio calculations. The analysis of the geometrical parameters, natural atomic charges and Wiberg bond indices, rotational energy surfaces and energies of the isodesmic reactions shows an essential contribution of pi-electron delocalization for the model butadienes 1, 5, 7, 9, and 10. On the contrary, in 2, 3 and 4 the stabilization due to the conjugation effects is negligible or in general absent. The NMR chemical shielding values, calculated for 1-10 with the GIAO procedure at the RHF/6-311 + G(d,p) level, as well as those published for the electron-rich butadienes (Me3Si)(2)C=P-X=C(NMe2)(2) (X = N, P), agree qualitatively with the global conception of Variation of the structural parameters and charge distribution due to the pi-electron delocalization in the molecules. (C) 2000 Elsevier Science B.V. All rights reserved.

Treatment of gem -dichlorocyclopropanecarboxylic acids with SF 4 yields many rearranged products, i.e. 1,1-difluoro-substituted olefins. The mechanism of the rearrangement is discussed.

The compounds C 6 H 5 XCF 3 and C 6 HXCH 3 (X=S, SO, SO 2 ) have been investigated by multinuclear 1 H, 13 C, 17 O, 19 F and 33 S NMR spectroscopy and quantum chemical methods (MNDO in the PM3 parametrization). Compounds with XCF 3 , SOCH 3 and SO 2 CH 3 groups have been characterized with effective non-planar conformations. A nearly planar effective conformation has been found for C 6 H 5 SCH 3 . As the two lone pairs (LP) of sulphur in the sulphides are essentially non-equivalent with their orbital energies differing considerably, only one LP (with a higher energy level) can participate in the p-π conjugation. In compounds with XCF 3 , SOCH 3 and SO 2 CH 3 groups, the electron-withdrawing π-inductive effect is the main factor determining the π-charge distribution in the benzene ring. The p-π conjugation is essentially distorted in C 6 H 5 SCF 3 due to its various conformations. Electron-donating p-π conjugation only contributes considerably to the π-charge distribution in the benzene ring in C 6 H 5 SCH 3 . An interpretation of the NMR spectra of the considered compounds is given on the basis of the quantum chemical calculations.

A synthesis of 3H-1,3-benzazaphospholes starting from C-phosphorylated P(III) arylformamidines has been developed. Electron-donating substituents were found to enhance markedly the rate of the cyclization, with substituents at the meta position having the greatest effect. A plausible mechanism of the cyclization was proposed based on DFT calculations. (C) 2011 Elsevier Ltd. All rights reserved.

A series of chiral S- or O-alkyl thionoesters have been synthesized by treatment of trifluorothioacetyl- or 2,2,3,3-tetrafluorothiopropionyl chloride with corresponding thiols or alcohols. The thia-Diels-Alder reaction of the thionoesters with symmetrical 1,3-dienes proceeds with diastereoselectivity up to 60%. Structures of cycloaddition products and corresponding transition states have been studied at the DFT level of approximation. The experimentally observed diastereomeric excess has been referred to differences in activation energies of transition states, preceding formation of the diastereomeric cycloaducts. (C) 2009 Elsevier B.V. All rights reserved.

A simple and useful method has been proposed for preparing of 1-chloro-2,2,2-trifluoroethan sulfonylchloride. By aminolysis of 1-chloro-2,2,2-trifluoroethansulfonylchloride the chlorine migration proceeds forming the corresponding salts of 1,1-dichloro-2,2,2-trifluoroethansulfinic acid. This process as well as the alternative reaction, elimination of hydrogen halogenide, has been studied using quantum chemistry (DFT and MP2) methods. As the calculation data indicate, an intermediately formed anion undergo intramolecular chlorine migration via a three-membered cyclic transition state. The latter is characterized by the low activation energy (Delta E = 27.0 kcal/mol). The barrier of activation in the case of 1,2,2,2-tetrafluoroethansulfonylfluoride is considerably higher (Delta E = 41.6 kcal/mol). The structures of the 1,1-dichloro-2,2,2-trifluoroethan sulfinic acid and 1,1,2,2,2-pentafluoroethansulfinic acid anions can be considered as donor-acceptor complexes of perhalogenoalkyl anions with SO2. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.

Alkyl perfluoroalkanedithiocarboxylates have been synthesized from 1,1-dichloroperfluoroalkyl propyl sulfides by reaction with zinc sulfide or cadmium sulfide.

We synthesized the new supramolecular host molecules 7 and 13 based on functionalized resorcarenes bearing Kemp's triacid. Conformations in solution have been investigated and the influence of intra-and intermolecular hydrogen bonds from the triacid was shown by low temperature and DOSY NMR experiments. The results of host 7 are supported by DFT calculations. The binding behaviour of 7 towards different 2-amino pyridincs in chloroform has been investigated by NMR titrations. The association constants reach from K 207 M-1 for 2-amino-5-cyano pyridine to K=1551 M-1 for 2-amino-4-methyl pyridine. The association constants of the formed complexes of 7 with 2-amino pyridines were compared with those of the simple host systems 14 and 15 in order to evaluate the influence of the attached resorcarene host. (c) 2008 Elsevier Ltd. All rights reserved.

The synthesis of calix[4]arenes bearing two quinazolin-4-ones group at the upper rim is decribed. H-1 NMR spectra and quantum chemical calculations make it possible to suggest that calix[4]arenequinazolinones form three rotamers in solutions at room temperature, due to the restricted rotation of the quinazolinone fragments. The X-ray structure investigation indicates that quinazolin-4-onecalix[4]arene exists in the crystal state as the methanol 1: 1 inclusion complex. (C) 2007 Elsevier Ltd. All rights reserved.

Treatment of 4-fluoro-5-(1,1,2,2-tetrafluoroethyl)-3H-1,2-dithiole-3-thione with 2 equivalents of sodium sulfide gives after acidification 3,4-difluoro-2-mercapto-1,6,6a gimel(4)-trithiapentalene, which can be further reduced by sodium sulfide to 3,5-difluoro-4-mercapto-thiopyran-2-thione. (c) 2006 Elsevier B.V. All rights reserved.

Recently a new type of calix[4]arenes has been synthesized via condensation of 2,6-dihydroxypyridine and a number of aldehydes. This type of pyridine[4]arenes forms capsules consisting of two single pyridine[4]arenes. These capsules can incorporate different guest molecules, like carboxylic acids and amides in this case. We proved that the guest acids really are incorporated inside the cavity of the capsules by electrospray mass spectrometry, NMR spectroscopy, and theoretical calculations.

A broad range of (phosphino)(aryl)carbenes, 1b-d, 10a,b, and 14a,b, were prepared by photolysis of their diazo precursors. The influence of the steric and electronic properties of the aryl ring on the structure and stability of these carbenes was studied both experimentally and theoretically. Among the different stabilization modes investigated, those featuring an acceptor as well as a spectator aryl substituent result in stable or at least persistent carbenes that could be completely characterized by classical spectroscopic methods. In marked contrast, the new substitution pattern featuring a donor aryl ring results in a very fleeting carbene.

The formation of coordination compounds of phosphanyl carbenes with a transition metal in a high oxidation state (Schrock type) is evaluated by density functional theory. In the Schrock type carbene complexes the transition metal-carbon bond possesses a multiple bond character. If one of the ligands at the carbene center possesses a leaving ability, e.g. as the diaminophosphenium unit, a facile distortion to a new type of an anionic metallaalkylidene donor-acceptor complex with a diaminophosphenium cation is predicted. (C) 2001 Elsevier Science B.V. All rights reserved.

The formation of a Fischer-type transition metal complex with a W(CO)(5) fragment is evaluated for the phosphanylcarbenes, Arduengo-type carbenes, and Bertrand-type carbenes by means of quantum chemical investigations at a density functional level with effective core potential methods. Accordingly, the stabilities of the complexes depend strongly on the substitution pattern of the carbenic unit. Amino-substituted carbenes as well as the Arduengo-type carbene form stable transition metal complexes. The stabilities of the complexes decrease for the phosphanylcarbenes and are at a minimum for the hitherto unknown transition metal complexes of the push-pull-type carbene of Bertrand. The matter is analyzed in terms of distortion energies required to bring the carbene units into the geometrical standard state for complexation with the transition metal fragment. The arguments evaluated for the phosphanylcarbenes should hold equally well for other carbenes substituted with electropositive ligands. For the mono-phosphanylcarbenes, eta (1) as well as eta (2) structures are investigated. For the diphosphanylcarbenes, a new structural type of metal complexes is predicted in which the transition metal fragment is strongly bound to a cyclic structural valence isomer of the carbene.

1,1-Dichloropolyfluoropentylsulfenyl chlorides react with lithium hexamethyldisilylamide with the formation of N,N -bis(trimethylsilyl)- 1-chloro-polyfluoropentyl-1-en-sulfenamide.

A wide series of low-coordinated phosphorus (III) compounds including iminophosphines 1, two- 2 or mono-coordinated 3 phosphorus-containing cations, and anion 4, where Mes∗ = 2,4,6-tris-(tert-butyl)phenyl, has been investigated by 13C, 15N and 31P NMR spectroscopy. The spectral parameters obtained are considered in connection with the ab initio (6–31G∗) calculation data of the model compounds.

Several recent developments in our laboratories have made it possible to elaborate a general method for preparing optically pure fluorine containing α-amino acids starting from a Ni(II)-complex ( 1 ) of a Schiff's base derived from (S)-o-[(benzylpropyl)amino]-benzophenone (BBP) and glycine or alanine. Alkylation of ( 1 ) with fluorine-substituted benzyl halides and aldehyde condensation result, respectively, in fluorine-containing S-Phe and its α-methyl derivatives, 2R,3S-, 2S,3R-, 2R,3R-PhSer and 2S,3S-β-perfluoroalkyl Ser in good chemical and optical yields. Simplicity of the synthetic procedure, ease of recovery of the chiral auxiliary (BBP), and the possibility of obtaining optically pure fluorine containing amino acids make this method attractive. The influence of fluorine atoms or fluorine containing groups and reaction conditions on the stereochemical results in the reactions of this type will be discussed.

Anopheles darlingi is the main vector of malaria in Brazil, characterized by a high level of anthropophilia and endophagy. Imidacloprid, thiacloprid, and acetamiprid are the most widespread insecticides of the neonicotinoid group. However, they produce adverse effects on the non-target insects. Flupyradifurone has been marketed as an alternative to non-fluorinated neonicotinoids. Neonicotinoids containing trifluoroacethyl substituent reveal increased insecticidal activity due to higher hydrophobicity and metabolic stability. We synthesized novel neonicotinoid insecticides containing fluorinated acceptor groups and their interactions were estimated with the nicotinic acetylcholine receptor (nAChR) binding site by molecular docking studies, to evaluate their larvicidal activity against A. darlingi, and to assess their outdoor photodegradation behavior. New neonicotinoid analogues were prepared and characterized by NMR and mass-spectrometry. The synthesized molecules were modelled by time-dependent density functional theory and analyzed, their interaction with nAChR was investigated by molecular docking. Their insecticide activity was tested on Anopheles larvae collected in suburban area of Manaus, Brazil. Four new fluorinated neonicotinoid analogs were prepared and tested against 3rd instars larvae of A. darlingi showing high larvicidal activity. Docking studies reveal binding modes of the synthesized compounds and suggest that their insecticidal potency is governed by specific interactions with the receptor binding site and enhanced lipophilicity. 2-Chloro-5-(2-trifluoromethyl-pyrrolidin-1-ylmethyl)pyridine 5 showed fast degradation in water maintaining high larvicidal activity. All obtained substances possessed high larvicidal activity in low concentrations in 48 hours of exposure, compared to commercial flupyradifurone. Such activity is connected to a unique binding pattern of the synthesized compounds to insect's nAChR and to their enhanced bioavailability owing to introduction of fluorinated amino-moieties. Therefore, the compounds in question have a high potential for application as control agents for insects transmitting tropical diseases, and they will be less persistent in the environment. © 2020 da Silva Mesquita et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.