scholarly journals Investigation of the role of stereoelectronic effects in the conformation of piperidones by NMR spectroscopy and X-ray diffraction

2015 ◽  
Vol 11 ◽  
pp. 1973-1984 ◽  
Author(s):  
Cesar Garcias-Morales ◽  
David Ortegón-Reyna ◽  
Armando Ariza-Castolo
Keyword(s):  
Density Functional ◽  
Pulse Sequence ◽  
Lone Pair ◽  
Chair Conformation ◽  
Intramolecular Interactions ◽  
Coupling Constants ◽  
Boat Conformation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Stereoelectronic Effects

This paper reports the synthesis of a series of piperidones 1–8 by the Mannich reaction and analysis of their structures and conformations in solution by NMR and mass spectrometry. The six-membered rings in 2,4,6,8-tetraphenyl-3,7-diazabicyclo[3.3.1]nonan-9-ones, compounds 1 and 2, adopt a chair–boat conformation, while those in 2,4-diphenyl-3-azabicyclo[3.3.1]nonan-9-ones, compounds 3–8, adopt a chair–chair conformation because of stereoelectronic effects. These stereoelectronic effects were analyzed by the 1 J C–H coupling constants, which were measured in the 13C satellites of the 1H NMR spectra obtained with the hetero-dqf pulse sequence. In the solid state, these stereoelectronic effects were investigated by measurement of X-ray diffraction data, the molecular geometry (torsional bond angles and bond distances), and inter- and intramolecular interactions, and by natural bond orbital analysis, which was performed using density functional theory at the ωB97XD/6311++G(d,p) level. We found that one of the main factors influencing the conformational stability of 3–8 is the interaction between the lone-pair electrons of nitrogen and the antibonding sigma orbital of C(7)–Heq (nN→σ*C–H(7)eq), a type of hyperconjugative interaction.

Crystal structure determination of the conformation of two bicyclo[3.3.1]nonan-ones

1985 ◽  
Vol 63 (6) ◽  
pp. 1166-1169 ◽  
Author(s):  
John F. Richardson ◽  
Ted S. Sorensen
Keyword(s):  
Crystal Structure ◽  
Direct Methods ◽  
Chair Conformation ◽  
Molecular Structures ◽  
Boat Conformation ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Final Agreement

The molecular structures of exo-7-methylbicyclo[3.3.1]nonan-3-one, 3, and the endo-7-methyl isomer, 4, have been determined using X-ray-diffraction techniques. Compound 3 crystallizes in the space group [Formula: see text] with a = 15.115(1), c = 7.677(2) Å, and Z = 8 while 4 crystallizes in the space group P21 with a = 6.446(1), b = 7.831(1), c = 8.414(2) Å, β = 94.42(2)°, and Z = 2. The structures were solved by direct methods and refined to final agreement factors of R = 0.041 and R = 0.034 for 3 and 4 respectively. Compound 3 exists in a chair–chair conformation and there is no significant flattening of the chair rings. However, in 4, the non-ketone ring is forced into a boat conformation. These results are significant in interpreting what conformations may be present in the related sp2-hybridized carbocations.

scholarly journals Synthesis of Trithia-Borinane Complexes Stabilized in Diruthenium Core: [(Cp*Ru)2(η1-S)(η1-CS){(CH2)2S3BR}] (R = H or SMe)

Inorganics ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 21 ◽  
Author(s):  
Koushik Saha ◽  
Urminder Kaur ◽  
Rosmita Borthakur ◽  
Sundargopal Ghosh
Keyword(s):  
Mass Spectrometry ◽  
1H Nmr Spectroscopy ◽  
Chair Conformation ◽  
Membered Ring ◽  
Molecular Structures ◽  
Boat Conformation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Butterfly Cluster ◽  
Tellurium Powder

The thermolysis of arachno-1 [(Cp*Ru)2(B3H8)(CS2H)] in the presence of tellurium powder yielded a series of ruthenium trithia-borinane complexes: [(Cp*Ru)2(η1-S)(η1-CS){(CH2)2S3BH}] 2, [(Cp*Ru)2(η1-S)(η1-CS){(CH2)2S3B(SMe)}] 3, and [(Cp*Ru)2(η1-S)(η1-CS){(CH2)2S3BH}] 4. Compounds 2–4 were considered as ruthenium trithia-borinane complexes, where the central six-membered ring {C2BS3} adopted a boat conformation. Compounds 2–4 were similar to our recently reported ruthenium diborinane complex [(Cp*Ru){(η2-SCHS)CH2S2(BH2)2}]. Unlike diborinane, where the central six-membered ring {CB2S3} adopted a chair conformation, compounds 2–4 adopted a boat conformation. In an attempt to convert arachno-1 into a closo or nido cluster, we pyrolyzed it in toluene. Interestingly, the reaction led to the isolation of a capped butterfly cluster, [(Cp*Ru)2(B3H5)(CS2H2)] 5. All the compounds were characterized by 1H, 11B{1H}, and 13C{1H} NMR spectroscopy and mass spectrometry. The molecular structures of complexes 2, 3, and 5 were also determined by single-crystal X-ray diffraction analysis.

Intra- and intermolecular interactions in a series of chlorido-tricarbonyl-diazabutadienerhenium(I) complexes: structural and theoretical studies

2020 ◽  
Vol 76 (3) ◽  
pp. 417-426 ◽  
Author(s):  
Reza Kia ◽  
Azadeh Kalaghchi
Keyword(s):  
Intermolecular Interactions ◽  
Density Functional ◽  
Metal Carbonyl ◽  
Lone Pair ◽  
Carbonyl Complexes ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Covalent Interaction ◽  
Metal Carbonyl Complexes

A series of new chlorido-tricarbonylrhenium(I) complexes bearing alkyl-substituted diazabutadiene (DAB) ligands, namely N,N′-bis(2,4-dimethylbenzene)-1,4-diazabutadiene (L1), N,N′-bis(2,4-dimethylbenzene)-2,3-dimethyl-1,4-diazabutadiene (L2), N,N′-bis(2,4,6-trimethylbenzene)-2,3-dimethyl-1,4-diazabutadiene (L3) and N,N′-bis(2,6-diisopropylbenzene)-1,4-diazabutadiene (L4), were synthesized and investigated. The crystal structures have been fully characterized by X-ray diffraction and spectroscopic methods. Density functional theory, natural bond orbital and non-covalent interaction index methods have been used to study the optimized geometry in the gas phase and intra- and intermolecular interactions in the complexes, respectively. The most important studied interactions in these metal carbonyl complexes are n→π*, n→σ* and π→π*. Among complexes 1–4, only 2 shows interesting intermolecular n→π* interactions due to lp(C[triple-bond]O)...π* and lp(Cl)...π* (lp = lone pair) contacts.

A cyanide-bridged FeIII–MnII heterobimetallic one-dimensional coordination polymer: synthesis, crystal structure, experimental and theoretical magnetism investigation

2019 ◽  
Vol 75 (11) ◽  
pp. 1475-1481 ◽  
Author(s):  
Wenlong Lan ◽  
Zhen Zhou ◽  
Jie Li ◽  
Yong Dou ◽  
Xiaoyun Hao ◽  
...  
Keyword(s):  
Coordination Polymer ◽  
Single Crystal ◽  
Density Functional ◽  
Linear Chain ◽  
Coupling Constants ◽  
Antiferromagnetic Coupling ◽  
Chain Model ◽  
X Ray Diffraction ◽  
One Dimensional ◽  
X Ray

A new cyanide-bridged FeIII–MnII heterobimetallic coordination polymer (CP), namely catena-poly[[[N,N′-(1,2-phenylene)bis(pyridine-2-carboxamidato)-κ4 N,N′,N′′,N′′′]iron(III)]-μ-cyanido-κ2 C:N-[bis(4,4′-bipyridine-κN)bis(methanol-κO)manganese(II)]-μ-cyanido-κ2 N:C], {[FeMn(C18H12N4O2)(CN)2(C10H8N2)2(CH3OH)2]ClO4} n , (1), was prepared by the self-assembly of the trans-dicyanidoiron(III)-containing building block [Fe(bpb)(CN)2]− [bpb2− = N,N′-(1,2-phenylene)bis(pyridine-2-carboxamidate)], [Mn(ClO4)2]·6H2O and 4,4′-bipyridine, and was structurally characterized by elemental analysis, IR spectroscopy, single-crystal X-ray crystallography and powder X-ray diffraction (PXRD). Single-crystal X-ray diffraction analysis shows that CP 1 possesses a cationic linear chain structure consisting of alternating cyanide-bridged Fe–Mn units, with free perchlorate as the charge-balancing anion, which can be further extended into a two-dimensional supramolecular sheet structure via inter-chain π–π interactions between the 4,4′-bipyridine ligands. Within the chain, each MnII ion is six-coordinated by an N6 unit and is involved in a slightly distorted octahedral coordination geometry. Investigation of the magnetic properties of 1 reveals an antiferromagnetic coupling between the cyanide-bridged FeIII and MnII ions. A best fit of the magnetic susceptibility based on the one-dimensional alternating chain model leads to the magnetic coupling constants J 1 = −1.35 and J 2 = −1.05 cm−1, and the antiferromagnetic coupling was further confirmed by spin Hamiltonian-based density functional theoretical (DFT) calculations.

Configurations and conformations of glycosyl sulfoxides

2010 ◽  
Vol 88 (11) ◽  
pp. 1154-1174 ◽  
Author(s):  
Hong Liang ◽  
Micheline MacKay ◽  
T. Bruce Grindley ◽  
Katherine N. Robertson ◽  
T. Stanley Cameron
Keyword(s):  
Solid State ◽  
Dft Calculations ◽  
Gas Phase ◽  
Density Functional ◽  
Lone Pair ◽  
Azido Group ◽  
X Ray Diffraction ◽  
X Ray ◽  
Comparison Of The Results ◽  
P Type

X-ray crystallographic studies of two axial glycosyl sulfoxides having RS configurations (derivatives of phenyl 2-azido-2-deoxy-1-thio-α-d-galactopyranoside S-oxide) show that they adopt anti conformations in the solid state, in contrast to previous observations and assumptions. Density functional theory (DFT) calculations at the B3lYP6–311G+(d,p)/6–31G(d) level confirm that anti conformations of both phenyl and methyl RS glycosyl sulfoxides of 2-azido-2-deoxy-α-d-pyranosides are more stable than exo-anomeric conformations in the gas phase. 1D NOE measurements indicate that the more polar exo-anomeric conformers are only populated to a slight extent in solution. The anti conformations are distorted so that the glycosyl substituents are closer to being eclipsed with H1. This distortion allows S n → σ* overlap if the sulfur lone pair is a p-type lone pair. Evidence for this overlap comes from short C1–S bond distances, as short as the comparable bond distances in the X-ray crystal structure and in the results from DFT calculations for the SS glycoside, which does adopt the expected exo-anomeric conformation, both in the solid state and in solution, and has normal n → σ* overlap. For 2-deoxy derivatives not bearing a 2-azido group, gas-phase DFT calculations at the same level indicate that the anti- and exo-anomeric conformers have comparable stabilities. Comparison of the results of the two series shows that electronegative substituents in equatorial orientations at C2 destabilize conformations with parallel S–O arrangements, the conformation favored by having an endocyclic C–O dipole antiparallel to the S–O dipole, by about 2.5 kcal mol–1 (1 cal = 4.184 J). An equatorial glycosyl sulfoxide, (SS) phenyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-1-thio-β-d-glucopyranoside S-oxide, also adopts an anti conformation in the solid state as shown by X-ray diffraction. It also adopts this conformation in solution, in contrast to studies of other equatorial glycosyl sulfoxides.

Stereochemistry of Substituted Isomeric 3-Oxa-7-aza-bicyclo[3.3.1]nonan-9-ones

1987 ◽  
Vol 42 (2) ◽  
pp. 221-228 ◽  
Author(s):  
Horst Küppers ◽  
Karl-F. Hesse ◽  
Ulrike Ashauer-Holzgrabe ◽  
Rolf Haller ◽  
Roland Boese
Keyword(s):  
Nmr Spectroscopy ◽  
Nitrogen Atom ◽  
Crystal Structures ◽  
Chair Conformation ◽  
Heterocyclic Ring ◽  
Boat Conformation ◽  
Bulky Substituent ◽  
X Ray Diffraction ◽  
Triclinic Space Group ◽  
X Ray

Abstract Two isomers of 7-methyl-9-oxo-2,4-diphenyl-3-oxa-7-aza-bicyclo[3.3.1]nonan-1,5-ethyl dicarboxylate (1a and 1b) were obtained by condensation of 2,6-diphenyl-1-oxa-4-oxo-cyclohexan-3,5-ethyl dicarboxylate with methylamine and formaldehyde. Their crystal structures were determined by X-ray diffraction. They crystallize in the triclinic space group P1̄ with (for 1a) a = 12.907(5), b = 11.223(4), c = 8.993(4) Å, α = 105.82(4), β = 100.14(5), γ = 97.35(4)°, and (for 1b) a = 16.400(7), b = 13.062(4), c = 11.336(2) Å, α = 94.19(3), β = 94.74(3), γ = 102.56(4)°. This investigation has shown that isomer 1a has the boat-chair conformation, and isomer 1b has the chair-chair conformation. The formation of la causes a configurational change of the phenyl substituents. The two species are characterized by NMR spectroscopy. - Another comparable bicyclononanone with a bulky substituent at the nitrogen atom has been synthesized and was investigated spectroscopically. This compound should have chair-boat conformation (with the boat conformation in the N-heterocyclic ring) whereas 1a has the boat conformation in the O-heterocyclic ring.

Total assignment of the 13C spectrum of taraxasteryl acetate by 13C–13C connectivity experiments and determination of the stereochemistry of taraxasterol by X-ray diffraction

1985 ◽  
Vol 63 (5) ◽  
pp. 1048-1054 ◽  
Author(s):  
William F. Reynolds ◽  
Jeffery F. Sawyer ◽  
Raúl G. Enriquez ◽  
Laura I. Escobar ◽  
Marco A. Chavez ◽  
...  
Keyword(s):  
Coupling Constants ◽  
Boat Conformation ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Chair Form ◽  
X Ray ◽  
Ethanol Solvate ◽  
Similar Conformation ◽  
Spectral Assignment

13C–13C connectivity (INADEQUATE) experiments have been used to reassign the 13C spectrum of taraxasteryl acetate. This shows that there were ten errors in an earlier 13C spectral assignment for this compound. An X-ray diffraction investigation of taraxasterol shows that ring E adopts a slightly distorted boat conformation. It is suggested that severe steric interactions in the chair form force it to adopt this unusual conformation. On the basis of the 1H–1H coupling constants, it is concluded that taraxasteryl acetate adopts a very similar conformation in solution. Crystals of taraxasterol–ethanol solvate are orthorhombic, space group P21,21,21, wih a = 7.447(1) Å, b = 17.637(2) Å, c = 22.269(4) Å, U = 2925 Å3, and Dcalc = 1.07 g cm−3 for Z = 4.

Chemistry of transition-metal complexes containing functionalized phosphines: synthesis and structural analysis of rhodium(I) complexes containing allyl and cyanoalkylphosphines

2020 ◽  
Vol 76 (9) ◽  
pp. 932-946
Author(s):  
Reinaldo Atencio ◽  
Gustavo Chacón ◽  
Lisbeth Mendoza ◽  
Teresa González ◽  
Julia Bruno-Colmenarez ◽  
...  
Keyword(s):  
Density Functional ◽  
Three Dimensional ◽  
Coupling Constants ◽  
Molecular Surface ◽  
Planar Geometry ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Conformational Preferences ◽  
Square Planar

A series of related acetylacetonate–carbonyl–rhodium compounds substituted by functionalized phosphines has been prepared in good to excellent yields by the reaction of [Rh(acac)(CO)2] (acac is acetylacetonate) with the corresponding allyl-, cyanomethyl- or cyanoethyl-substituted phosphines. All compounds were fully characterized by 31P, 1H, 13C NMR and IR spectroscopy. The X-ray structures of (acetylacetonato-κ2 O,O′)(tert-butylphosphanedicarbonitrile-κP)carbonylrhodium(I), [Rh(C5H7O2)(CO)(C8H13N2)] or [Rh(acac)(CO)(tBuP(CH2CN)2}] (2b), (acetylacetonato-κ2 O,O′)carbonyl[3-(diphenylphosphanyl)propanenitrile-κP]rhodium(I), [Rh(C5H7O2)(C15H14N)(CO)] or [Rh(acac)(CO){Ph2P(CH2CH2CN)}] (2h), and (acetylacetonato-κ2 O,O′)carbonyl[3-(di-tert-butylphosphanyl)propanenitrile-κP]rhodium(I), [Rh(C5H7O2)(C11H22N)(CO)] or [Rh(acac)(CO){tBu2P(CH2CH2CN)}] (2i), showed a square-planar geometry around the Rh atom with a significant trans influence over the acetylacetonate moiety, evidenced by long Rh—O bond lengths as expected for poor π-acceptor phosphines. The Rh—P distances displayed an inverse linear dependence with the coupling constants J P-Rh and the IR ν(C[triple-bond]O) bands, which accounts for the Rh—P electronic bonding feature (poor π-acceptors) of these complexes. A combined study from density functional theory (DFT) calculations and an evaluation of the intramolecular H...Rh contacts from X-ray diffraction data allowed a comparison of the conformational preferences of these complexes in the solid state versus the isolated compounds in the gas phase. For 2b, 2h and 2i, an energy-framework study evidenced that the crystal structures are mainly governed by dispersive energy. In fact, strong pairwise molecular dispersive interactions are responsible for the columnar arrangement observed in these complexes. A Hirshfeld surface analysis employing three-dimensional molecular surface contours and two-dimensional fingerprint plots indicated that the structures are stabilized by H...H, C...H, H...O, H...N and H...Rh intermolecular interactions.

The Electron Effect of Aromatic Group: Control Conformation of 2-Aromatic Cyclododecanone Derivatives

2020 ◽  
Vol 24 (10) ◽  
pp. 1139-1147
Author(s):  
Yang Mingyan ◽  
Wang Daoquan ◽  
Wang Mingan
Keyword(s):  
1H Nmr ◽  
13C Nmr ◽  
Nmr Spectra ◽  
Coupling Constants ◽  
The Other ◽  
Repulsive Interaction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Electron Effect ◽  
Group Control

2-Phenylcyclododecanone and 2-cyclohexylcyclododecanone derivatives were synthesized and characterized by 1H NMR, 13C NMR, HR-ESI-MS and X-ray diffraction. Their preferred conformations were analyzed by the coupling constants in the 1H NMR spectra and X-ray diffraction, which showed the skeleton ring of these derivatives containing [3333]-2-one conformation, and the phenyl groups were located at the side-exo position of [3333]-2-one conformation due to the strong π-π repulsive interaction between the π- electron of benzene ring and π-electron of carbonyl group. The cyclohexyl groups were located at the corner-syn or the side-exo position of [3333]-2-one conformation depending on the hindrance of the other substituted groups. The π-π electron effect played a crucial role in efficiently controlling the preferred conformation of 2-aromatic cyclododecanone and the other 2-aromatic macrocyclic derivatives with the similar preferred square and rectangular conformations.

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