Double Chair Conformation Research Articles

Ligand Induced Double-Chair Conformation Ln12 Nanoclusters Showing Multifunctional Magnetic and Proton Conductive Properties.

Many methods have been utilized to adjust the size of superatomic metal nanoclusters, while tuning the geometric conformations of specific nanoclusters is rare. Here, we demonstrate that conformation variation can be realized by slightly modifying the ligand under maintaining the nuclei number of metal atoms. A series of novel "double-chair" conformation Ln12 (Ln = Sm (1), Eu (2), Gd (3), Tb (4), and Dy (5)) clusters were generated by replacing 3-formylsalicylic acid with 2,3-dihydroxybenzoic acid in the Ln12 nanocluster. Intriguingly, Dy12 displays slow magnetic relaxation at low temperatures, while Gd12 shows a large magnetocaloric effect (MCE) of 35.63 J kg-1 K-1 at 2 K for ΔH = 7 T. Additionally, the introduction of numerous coordination water molecules in these clusters enables Dy12 and Gd12 with high proton conductivity, namely, 2.13 × 10-4 and 3.62 × 10-4 S cm-1 under 358 K and 95% RH humidity conditions.

Bispidine-based bis-azoles as a new family of supramolecular receptors: the theoretical approach

Two new bis-azoles derived from 1,5-dimethylbispidin-9-one were synthesized and structurally characterized. In both cases the bispidine backbone adopts the double chair conformation, which is also confirmed by calculations. In both structures, the azole rings are spatially pre-reorganized for the supramolecular interactions with the proper substrates like electron-rich aromatic compounds; the origin and nature of tiny intramolecular interactions are discussed in view of conformation stability.

Synthesis and Myelostimulatory Activity of a Number of 3,7-Diazabicyclo[3.3.1]Nonane Derivatives

Mannich condensation was used to synthesize new bispidinones, Wolff-Kishner reduction of which produced the corresponding bispidanes. 1H NMR spectroscopy studies showed that these existed in the double chair conformation. The myelostimulatory activity of the compounds synthesized here was assessed.

Cинтез и миелостимулирующая активность некоторых производных 3,7-диазабицикло[3.3.1]нонана

Конденсацией по Манниху синтезированы новые биспидиноны, восстановление которых по Кижнеру – Вольфу привело к соответствующим биспидинам. На основании ЯМР 1H спектроскопии установлено, что они существуют в конформации двойного кресла. Изучена миелостимулирующая активность синтезированных соединений.

2,4-Bis(2-methoxyphenyl)-3-azabicyclo[3.3.1]nonan-9-one

In the title compound, C22H25NO3, the mol­ecule has a pseudo-mirror plane. The structure is a positional isomer of 2,4-bis(4-methoxy­phenyl)-3-aza­bicyclo­[3.3.1]nonan-9-one [Cox, McCabe, Milne & Sim (1985 ▶). J. Chem. Soc. Chem. Commun. pp. 626–628]. The 3-aza­bicyclo­[3.3.1]nonan-9-one moiety adopts a double chair conformation with equatorial orientations of both 2-methoxy­phenyl substituents on either side of the secondary amino group. The benzene rings are oriented at an angle of 33.86 (4)° with respect to each other and the meth­oxy groups point towards the carbonyl group. The crystal structure is stabilized by intermolecular N—H⋯π inter­actions.

1H NMR spectroscopy in the study of the three-dimensional structure of 7-alkoxyalkyl-3-thia-7-azabicyclo-[3.3.1]nonan-9-ones and some of their derivatives

1 H NMR spectroscopy was used to establish that 7-alkoxyalkyl-3-thia-7-azabicyclo[3.3.1]nonan-9-ones and their decarbonylated derivatives in deuterochloroform solution exist in the double chair conformation. The predominantly formed secondary alcohols isomers have preferred double chair conformation with the hydroxyl group equatorial relative to the plane of the piperidine ring. On the other hand, the epimeric alcohols have predominant boat-chair conformation; the piperidine ring takes the boat form due to intramolecular hydrogen bonding between the unshared electron pair of the nitrogen atom and hydroxyl group proton.

Cis-9,10-Bis(bromomethyl)-1,4,5,8-tetraoxadecalin

The title compound, C8H12Br2O4, is a bicyclic ketal in which the two six-membered rings are cis to one another and assume a double-chair conformation. A crystallographic twofold axis bisects the molecule.

Study of the Steric Structure of 7-Alkoxyalkyl-3-oxa-7-azabicyclo[3.3.1]nonan-9-ones and Their Derivatives Using1H NMR Spectroscopy

Using the 1H NMR spectroscopic method it has been shown that 7-alkoxyalkyl-3-oxa-7-azabicyclo[3.3.1]nonan-9-ones and 7-alkoxyalkyl-3-oxa-7-azabicyclo[3.3.1]nonanes exist in deuterochloroform solution in a double chair conformation. 7-(3-Butoxypropyl)-3-oxa-7-azabicyclo[3.3.1]nonan-9-ol is a 1:1 mixture of the two stereoisomeric alcohols. One of them exists in a double chair conformation having an equatorial hydroxyl group with relation to the piperidine ring and the other in a chair-boat conformation having an axial hydroxyl group which involves an intramolecular hydrogen bond with the unshared electron pair of the nitrogen atom.

Conformational behavior of 3-borabicyclo[3.3.1]nonanes

Abstract 3-Methoxy-7α-phenyl-1,5-dimethyl-3-borabicyclo[3.3.1]nonane 5 in solution at room temperature exists in the double chair conformation, as shown by NMR studies. Increasing the temperature leads to an increase in the population of the chair–boat conformation. At decreased temperature hindered rotation around the BO bond is observed for 5. Dissolving 5 in deuteropyridine leads to the reversible formation of complex 6, which exists in the chair–boat conformation. The chair–boat conformation is also the most stable one for chelate compound 7 with a tetracoordinated boron atom.

3-O-benzoyl-4,6;4',6'-di-O-benzylidene-2,2'-dideoxy,alpha,alpha-ribo- trehalose.

The low-temperature X-ray structure of an asymmetrically substituted derivative of alpha,alpha-trehalose, 3-O-benzoyl-4,6;4',6'-di-O-benzylidene-2,2'-dideoxy-alpha,alpha-ribo-tre halose (3-O-benzoyl-4,6-O-benzylidene-2-deoxy-alpha-D-ribo-hexopyranosyl 4,6-O-benzylidene-2-deoxy-alpha-D-ribo-hexopyranoside, C33H34O10), is reported. The hexopyranosyl rings and the 1,3-dioxane rings have normal 4C1 chair conformations, so that each half of the molecule has a double-chair conformation, resembling a trans-decalin ring system. Each benzylidene acetal group takes the form of the thermodynamically more stable (R)-diastereomer with its phenyl group attached to the 1,3-dioxane ring in an equatorial orientation. The conformations about the glycosidic linkages are stabilized by the anomeric effect and by an intramolecular hydrogen bond between the lone hydroxy group and the glycosidic O atom.

A novel dioxabicyclo[3.3.1]nonane, a key intermediate in the synthesis of erythronolide B seco-acid.

In the title compound, (1R,4S,5R,6R,8R)-1-ethyl-4,6,8-trimethyl-2,9-dioxabicyclo[3.3.1]++ +nonan-6-yl 1-imidazolecarboxylate, C16H24N2O4, the 2,9-dioxabicyclo[3.3.1]nonane ring system assumes a double-chair conformation. Bond angles around the ring are enlarged compared to normal tetrahedral values to alleviate some of the overcrowding which results from close intramolecular H...H and C...C contacts. The N-imidazolylcarbonyloxy group is nearly planar with dihedral angles of 5.2 (2) and 6.0 (2) degrees between the imidazole and carbonyl groups for molecules 1 and 2, respectively.

Synthesis and structural study of 9-(2′-hydroxyethyl)-9-azabicyclo[3.3.1]nonan-3α-OL

The infrared, 1H and 13C NMR spectra of 9-(2′-hydroxyethyl)-9-azabicyclo[3.3.1] nonan-3α-ol (I) have been examined in several media. The crystal structure has been determined by X-ray diffraction. The bicycle system adopts in solid state a distorted double chair conformation, being the OH and 2′-hydroxyethyl group attached in axial position with respect to the piperidinol ring. In solution, by the contrary, the title compound adopts a preferred flattened chair-boat conformation with the piperidinol ring in a slight distorted boat form. The unambiguous assignment of all protons of the granatanine system, not described up to date, has been carried out.

A dynamic 1H and 13C nuclear magnetic resonance study of cis-1,6-dimethyl-2,5,7,10-tetraoxabicyclo[4.4.0]decane (4a,8a-dimethylhexahydro-p-dioxino[2,3-b]-p-dioxin)

The 1H and 13C n.m.r. spectra of cis-1,6-dimethyl-2,5,7,10-tetraoxabicyclo[4.4.0]decane have been studied over a wide temperature range (204–293 K). Temperature-dependent phenomena observed in both the 1H and 13C n.m.r. spectra can be attributed to a ring-inversion process between the enantiomeric forms of a double-chair conformation for the title compound. Line-shape analysis has been performed to obtain thermodynamic parameters for the ring-inversion process of these enantiomers. Molecular mechanics calculations have been used to obtain the minimum-energy conformation and to make structural comparisons with previous studies on 2,5,7,10-tetraoxabicyclo[4.4.0]decanes.

Organocarbon compounds : CCCXCIV. Reaction of 1-boraadamantane with carbonyl compounds

1-Boraadamantane has been shown to react with aromatic aldehydes, isobutyraldehyde, and acetone forming firstly the 1 : 1 complexes which at 70–80°C form new heterocyclic cage compounds: 5-substituted derivatives of 4-oxa-3-bora-1,1-bihomoadamantane (4-oxa-3-boratricyclo[5.3.1.1 3.9]dodecane) which exist as dimers. Starting from 4-oxa-5-(4-methoxyphenyl)-3-bora-1,1-bihomoadamantane and 4-oxa-5-(3,4-dimethoxyphenyl)-3-bora-1,1-bihomoadamantane, the corresponding 3-methoxy-7α-(2-methoxy-2-arylethyl)-3-borabicyclo[3.3.1]nonanes were obtained; the latter two compounds eliminate MeOH on heating in vacuum to give 3-methoxy-7α-(2-arylvinyl)-3-borabicyclo[3.3.1]nonanes, which exist in the double chair conformation, as shown by 1H and 13C NMR spectroscopy.

The conformation of (1R,2S,4R,5S)‐2,4‐dimethoxybicyclo[3.3.1]nonan‐9‐one and some related compounds

AbstractA mixture of stereoisomers of 2,4‐dimethoxybicyclo[3.3.1]nonan‐9‐one was prepared, separated by column chromatography and characterized by 60 MHz 1H NMR spectroscopy using Eu(fod)3. A double chair conformation with axial methoxyl groups is established for (1R,2S,4R,5S)‐2,4‐dimethoxybicyclo[3.3.1]‐nonan‐9‐one on the basis of the J(12), J(2,H‐3 exo) and J(2,3 endo) values and the chemical shifts for H‐2(4). The conformation of some related compounds is subsequently inferred.

Conformational analysis of 3-borabicyclo[3.3.1]nonane derivatives

Conformations of 3-borabicyclo[3.3.1]nonane derivatives have been studied by means of 1H and 13C NMR spectroscopy. With the aid of the coupling constants 3J(HH) and 13C chemical shifts it has been shown that all the derivatives of 3-borabicyclo[3.3.1]nonane with the trigonal boron atom studied are in a flattened double-chair conformation. In 3-borabicyclo[3.3.1]nonane derivatives with the tetra-coordinated boron atom and substituents at the 7α-position, the chair-boat conformation predominates, the boat conformation being characteristic of the cyclohexane ring; exceptions are the compounds with the internal donor—acceptor bond between the boron atom an 7α-substituent.

Direct observation of boat–chair ⇌ chair–boat equilibrium in the 3,7-diazabicyclo[3.3.1]nonane ring

Variable-temperature 13C n.m.r. spectra of 3,7-dialkyl-1,5-diazabicyclo[3.3.1]nonan-9-ones unambiguously establish a boat–chair ⇌ chair–boat equilibrium rather than the fixed double-chair conformation which had previously been proposed.

Stéréochimie de β-diols et de leurs dérivés cycliques. X. Etude structurale en résonance magnétique nucléaire du proton de dioxanne-1,3-4-spirocyclohexanes: méthyl-2 dioxanne-1,3-4-spiro-tert-butyl-4′ cyclohexanes-cis et -trans (série I)

The two title compounds serve as models for an eventual structural study of two more complex series. High field nmr spectral analysis using INDOR or solvent effects allows us to assign nearly all proton signals and to propose that these compounds exist in the double chair conformation. Finally, chemical shifts in CCl4 have been used to evaluate the effect of the intracyclic oxygen atoms on the 2′ and 6′ proton nmr resonances of the spirobicyclohexane. [Journal translation]

Stéréochimie de β-diols et de leurs dérivés cycliques. XIII. Etude structurale en résonance magnétique nucléaire du proton de dioxanne-1,3-4-spirocyclohexanes: tert-butyl-6-c méthyl-2-r (série II) et diméthyl-2-r, 5-t ou 5-c (série III) dioxanne-1,3-4-t ou -c-spirotriméthyl-3′,3′,5′-cyclohexanes-trans ou -cis

The nmr spectra at 60, 100, and 250 MHz in CCl4 of two series of four and eight diastereoisomers of the title 1,3-dioxanespiro-4-cyclohexanes have been analysed. In particular, use of the empirical calculation of chemical shifts allows for the unambiguous determination of structure without the need for chemical methods. With two exceptions, these compounds exist in the double chair conformation. In these molecules the γ intercyclic effect of the methyl groups in position 5 have been calculated. [Journal translation]

13C-NMR-Spektroskopische und stereochemische untersuchungen—XIV : Sessel- und bootkonformationen bei bicyclo[3.3.1]nonanverbindungen

Syntheses and 13C-NMR spectra of bicyclo[3.3.1]nonanes bearing substituents at C-1 (X = F, Cl, Br, J, OR) and C-3 (X = exo Cl, Br, OR; X = endo COOR, CH 3, OR) are described. The functional C α shifts are found to show the known dependence on the electron withdrawing effect of heterosubstituents, including the 1-jodo compound; there is, however, no weakening attenuation effect with tertiary compounds, as often implied, but rather substituent effects which are up to 25 ppm higher than observed with the corresponding secondary derivatives The β carbon shieldings of all compounds can be represented as a function of the square electric field effect; the flattening of the cyclohexane rings in the 1- and 3-exo-compounds however are resulting in a change of the linear electric field effects at C α, and even more at C γ. The deshielding of γ carbons in antipenplanar X-C α-C β-C γ conformations is not restricted to structures bearing X on a bridgehead, it can be rationalized on the basis of through space bond polarization by the C α-X dipoles (linear field effects). The very small upfield shifts generated by 3-exo-hetero-substituents at the C-7 position put an upper limit for pure through space long range shielding effects in 13C-NMR spectroscopy. With the exception of the 3-endo compounds the 13C shifts (as well as 13C- 19F couplings) of all compounds indicate a flattened double chair conformation CC The parameters found for the endo-3-derivatives establish the predominance of boat chair forms. Lanthanide induced shifts show the 3-endo substituent to rest at the boat part of the molecule. Although the shifts of the basic BC form for the unsubstituted hydrocarbon cannot be measured directly, they can be obtained by subtraction of corresponding substituent effects. Low temperature measurements establish the absence of higher populations of CC forms; the comparison of shift temperature gradients however indicates the partition of some CC conformer in the case of the endo-3-methoxy compound.