The values of the downfield chemical shift bridge hydrogen atom were estimated for a series compounds containing an intramolecular bond O-HO, O-HN, O-HHal, N-HO, N-HN, C-HO, C-HN and C-HHal. Based on these values, empirical estimation energy was obtained by using known relationships. For bond, DFT B3LYP/6-311++G(d,p) method used both geometry optimization QTAIM calculations topological parameters (electron density ρBCP potential V in critical point bond). calculated geometric bonds also to...

On the example of pyrrolylenones as D‒π‒A push-pull molecules with intramolecular charge transfer, common principles tuning HOMO and LUMO energy levels HOMO-LUMO gap due...

The energies of the O−H∙∙∙O=C intramolecular hydrogen bonds were compared quantitatively for series ortho-disubstituted benzenes and Z-isomers olefins via a molecular tailoring approach. It was established that bond energy in former is significantly less than latter one. reason lowering to decrease π-contribution total complex interaction, which per se enhanced by resonance effect. By example para- meta-disubstituted benzenes, as well E-isomers olefins, it explicitly shown aromatic ring much...

Abstract According to the 1 H, 13 C and 15 N NMR spectroscopic data DFT calculations, E ‐isomer of 1‐vinylpyrrole‐2‐carbaldehyde adopts preferable conformation with anti ‐orientation vinyl group relative carbaldehyde oxime syn ‐arrangement reference pyrrole ring. This is stabilized by CH···N intramolecular hydrogen bond between α‐hydrogen nitrogen, which causes a pronounced high‐frequency shift signal in H (∼0.5 ppm) an increase corresponding one‐bond C– coupling constant ( ca 4 Hz). In Z...

The (1)H, (13)C and (15)N NMR studies have shown that the E Z isomers of pyrrole-2-carbaldehyde oxime adopt preferable conformation with syn orientation group respect to pyrrole ring. is stabilized by N-H...N N-H...O intramolecular hydrogen bonds, respectively. bond in isomer causes high-frequency shift bridge proton signal about 1 ppm increase (1)J(N, H) coupling approximately 3 Hz. shows further deshielding higher constant due strengthening isomer. MP2 calculations indicate 3.5 kcal/mol...

Abstract A novel three‐component reaction between 1‐substituted imidazoles, aldehydes, and electron‐deficient acetylenes proceeds under mild conditions (20–25 °C, no catalyst, solvent) to form an unknown family of C2‐functionalized imidazoles in up 74 % yield, the function constituting a push–pull combination enol ether acrylic moieties. In case cyanophenylacetylene, is built stereospecifically have ( Z ) configuration. The interaction presumably occurs via zwitterion carbene intermediates....

Metal-free reaction between quinolines, aryltrifluoroacetylacetylenes and water resulted in stereoselective assembly of trifluoromethylated oxazinoquinolines with up to 99% yield.

Abstract The energy of the intramolecular hydrogen bond has been recognized and may be estimated by molecular fragmentation method based on functional dependence descriptor. Both basic methods for estimating bonds are compared using a series hydroxycarbonyl aliphatic compounds as benchmark. dependencies established that provide best fit with method. As both an have disadvantages, new hybrid approach is proposed. In this approach, average value calculated used parameter. provides compensation...

3-(1-Hydroxycyclohexyl)-2-propynenitrile reacts with tris[2-(4-pyridyl)ethyl]phosphine oxide to form mono-, bis- and tris{5-spirocyclohexyl-4-cyanomethylene-1,3-oxazolidine[3,2-a]-2-[4-(1,2-dihydropyridyl)]ethyl}phosphine oxides.

Abstract The introduction of a substituent in the 3‐position pyrrole ring N ‐vinyl‐2‐arylpyrroles and ‐2‐heteroarylpyrroles results an increase dihedral angles between planes aryl (or heteroaryl) residue, decrease angle vinyl group. Introduction 5‐position has opposite effect on these angles. For ‐vinyl‐2‐(2′‐furyl)pyrrole, some spectral data suggest formation CH…O hydrogen bond α‐hydrogen atom group oxygen furyl ring. This is accord with quantum chemical calculations.

First examples of direct vinylation 1-substituted imidazoles at the 2-position imidazole nucleus are described. 1-Substituted 1a−e C(2)-vinylated with 3-phenyl-2-propynenitrile (2) room temperature without catalyst and solvent to afford 3-(1-organyl-1H-imidazol-2-yl)-3-phenyl-2-propenenitriles 3a−e, mainly (c.a. 95%) as (Z)-isomers, in 56−88% yield. The reaction is likely involve zwitterionic intermediates, which prototropically isomerizes carbene eventually undergoes selective 3,2-shift...

Metal-free reaction between quinolines, aryltrifluoroacetylacetylenes and water resulted in stereoselective assembly of trifluoromethylated oxazinoquinolines up to 99% yield.

Abstract Using the molecular tailoring and function‐based approaches allows one to divide energy of O─H⋯O═C resonance‐assisted hydrogen bond in a series β‐diketones into resonance bonding components. The magnitude component is assessed as about 6 kcal mol −1 . This value increases by ca. 1 on going from weak strong bonding. varies wide range 2 20 depending structure β‐diketone question.

Several imines, readily derived from aryl methyl ketones and benzylamines, react with acetylene gas in KOBut/DMSO system to afford 2-azadienes stereoselectively. This new C-C bond constructing reaction involves, instead of the expected ethynylation C═N bond, addition azaallyl anions triple acetylene.

Abstract Context Hydrogen bonds critically influence the structure and properties of both organic molecules biomolecules, as well supramolecular assemblies. For this reason, development elaboration methods for quantitative assessment hydrogen bond energy is an urgent challenge. In study, using a large series hydroxycarbonyl aliphatic compounds with O‒H···O = C intramolecular bond, bank descriptors was created, including spectroscopic, structural, QTAIM-based, NBO-based parameters. It shown...

Abstract According to the 1 H, 13 C and 15 N NMR spectroscopic data ab initio calculations, strong NH···O intramolecular hydrogen bond in Z ‐isomers of 2‐(2‐acylethenyl)pyrroles causes decrease absolute size J (N,H) coupling constant by 2 Hz CDCl 3 4.5 DMSO‐ d 6 , deshielding proton nitrogen 5–6 ppm, respectively, lengthening NH link 0.025 Å. The NH···N 2(2′‐pyridyl)pyrrole leads increase Hz, 1.5 ppm 0.004 CH···N 1‐vinyl‐2‐(2′‐pyridyl)‐pyrrole results (C,H) 5 shortening CH 0.003...

Abstract In the 1 H and 13 C NMR spectra of 1‐(2‐selenophenyl)‐1‐alkanone oximes, H, C‐3 C‐5 signals selenophene ring are shifted by 0.1–0.4, 2.5–3.0 5.5–6.0 ppm, respectively, to higher frequencies, whereas those C‐1, C‐2 C‐4 carbons 4–5, ∼11 ∼1.7 ppm lower frequencies on going from E Z isomer. The 15 N chemical shift oximic nitrogen is larger 13–16 in isomer relative An extraordinarily large difference (above 90 ppm) between 77 Se resonance positions revealed studied oxime isomers, peak...

In the series of diaminoenones, large high-frequency shifts (1)H NMR N-H group in cis-position relative to carbonyl suggests strong N-H...O intramolecular hydrogen bonding comprising a six-membered chelate ring. The bond causes an increase (1)J(N,H) coupling constant by 2-4 Hz and shift (15)N signal 9-10 ppm despite lengthening relevant bond. These experimental trends are substantiated gauge-independent atomic orbital density functional theory calculations shielding constants...

Metal- and solvent-free reaction of quinolines with two molecules aryltrifluoroacetylacetylenes afforded 3-arylethynyl-3-trifluoromethyl-1,3-oxazinoquinolines in up to 92% yields. The formation a zwitterionic intermediate the first step triggered multistep domino reaction. This one-pot synthesis opens an easy access novel quinoline derivatives bearing trifluoromethyl, acetylene ketone functions, thus providing powerful tool for drug design.

Abstract According to the 1 H, 13 C and 15 N NMR spectroscopic data DFT calculations, bifurcated NH···N NH···O intramolecular hydrogen bond is shown be present in 2‐trifluoroacetyl‐5‐(2′‐pyridyl)‐pyrrole. This causes an increase absolute size of J (N,H) coupling constant by about 6 Hz, deshielding bridge proton 2 ppm. calculations show that influence bonds on shielding almost additive, although components slightly weaken each other. In 2‐trifluoroacetyl‐5‐(2′‐pyridyl)‐pyrrole, constants...