13C NMR spectroscopy of some 3- and 7-substituted bicyclo[3.3.1]nonanes

The ¹³C NMR spectra of a series of 3,7-substituted bicyclo[3.3.1]nonane derivatives are examined. Taken into account substituent influences, the ¹³C chemical shifts appear to be diagnostic for the conformation of the bicyclo[3.3.1]nonane derivative.     

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.     

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, CH₃, 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.     

Chair-boat equilibria in bicyclo[3.3.1]nonane and some 3- and 3,7-substituted derivatives: Thermodynamic parameters and geometry of the conformers as obtained by molecular mechanics

ΔG-Values for conformational equilibria in 3,7-substituted bicyclo[3.3.1]nonanes have been obtained by means of epimerisation experiments (cc α bc) and by variable temperature ¹³C NMR (bc α bb). The results of these experiments fit well with those of molecular mechanics using the Schleyer force field. In bicyclo[3.3.1]nonane and 3β-substituted derivatives the cc conformation predominates; however, the bulky 3β-substituent t-butyl, is found to have a destabilizing effect. A 3α-substituent forces the substituted wing into the boat conformation. For the 3α,7α-substituted derivatives the conformational preferences depend on the size of the substituents: for 3α-methyl-7α-t-butylbicyclo[3.3.1]nonane the cb and t-bb conformers are of approximately equal enthalpy. The geometries, obtained by the calculations, show that the conformers of bicyclo[3.3.1]nonane (cc, bc and t-bb) are all distinctly flattened. The boat wings of bc conformers are not twisted to any extent. The t-bb is the most stable bb conformation. The influence of substitution at positions 3 or 7 is discussed in detail; in general, a bulky substituent such as t-butyl, affects the geometry of both wings of the ring system. The calculated geometries are in good agreement with the conclusions of previous ¹H NMR investigations.     

Carbon-13 chemical shifts of bicyclo[3.2.1]octane and bicyclo[2.2.1]heptane derivatives

¹³C chemical shifts of more than fifty bicyclo[3.2.1]octane and bicyclo[2.2.1]heptane derivatives (hydrocarbons, alcohols, ketones and esters) have been determined. The usefulness of ethyl derivatives for the assignment of close ¹³C chemical shifts in bicyclic methyl derivatives is shown both for the bicyclo[3.2.1]octane and bicyclo[2.2.1]heptane series. Comparison of substituent effects on α-, β-, γ- and δ-carbons in both series of compounds shows remarkable differences in steric interactions. In contrast to the rigid bicyclo[2.2.1]heptane system, both chair and boat conformations can be predominant in the bicyclo[3.2.1]octane series with the conformationally flexible 6-membered ring.     

Carbon-13 NMR spectra of solid bicyclo[3. 3. 1]nonan-9-one. Conformational studies in the solid state

Carbon-13 NMR spectra of solid polycrystalline bicyclo[3.3.1]nonan-9-one and adamantanone have been measured at 315K. The relatively narrow ¹³C linewidths observed for these solids, together with measured spin-lattice relaxation times, indicate that both these solids are orientationally disordered. Observed ¹³C chemical shifts of solid bicyclo[3.3.1]nonan-9-one indicate a twin-chair conformation for the two cyclohexanone rings.     

13C NMR spectra of bicyclo[3.3.1]nonanones and their derivatives

Conclusions An assignment was made of the lines in the¹³C NMR spectra of the mono- and diketones of the bicyclo[3.3.1]nonane series, and of the hydrolysis products of bicyclo[3.3.1]nonane-2,9-dione and its 7-benzoyloxy derivative.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2386–2389, October, 1979.     

3,7-disubstituted bicyclo[3.3.1]nonanes—III: Synthesis and conformation of bicyclo[3.3.1]nonane-3α,7α-dicarboxylic acid,its dimethyl ester and some other 3,7-disubstituted bicyclo[3.3.1]nonanes; adamantane as an integrated holding system

The conformation of bicyclo[3.3.1]nonane-3α,7α-dicarboxylic acid and its dimethyl ester has been studied by comparing ¹H NMR and ¹³C NMR spectra of these compounds with those of some model 3,7-disubstituted bicyclo[3.3.1]nonanes, fixed in a single conformation by the use of adamantane as an integrated holding group or by means of suitable substitution. It is shown that the dicarboxylic acid and its dimethyl ester exist predominantly as two rapidly interconverting (identical) chair-boat conformations with distinctly flattened rings; the population of the double-boat conformation appears to be very small.     

13C and1H NMR spectra and structure of 2-aryl-1,3-dibenzoyl-1,3-diazabicyclo[3.3.1]nonanes

Conclusion ¹³C and¹H NMR spectroscopy was used to determine the structures of 2-aryl-1,3-dibenzoyl-1, 3-diazabicyclo[3.3.1]nonanes and 2-aryl-1-benzyl-3-benzoyl-1,3-diazabicyclo[3.3.1]nonane. These compounds were found to exist predominantly in the boat-chair conformation (boat for the diaza ring), while the 2-aryl substituents occupy the exo or endo position.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1023–1028, May, 1988.     

Intramolekulare Hydrostannierung - Cyclische und bicyclische Stannane

Intramolecular Hydrostannation — Cyclic and Bicyclic Stannanes Starting with (2-allyl-4-pentenyl)tin hydrides hydrostannation reactions are used to prepare 3-allyl-1-stannacyclohexanes and 1-methyl-1-stannabicyclo[3.3.1]nonane; i.r., ¹¹⁹Sn, and ¹³C n.m.r. data are presented.     

Solvolysis of 2-Bicyclo

The solvolysis rate of 2-bicyclo[3.2.2]nonyl p-toluenesulfonate (6-OTs) was nearly equal to that of cycloheptyl p-toluenesulfonate in 2,2,2-trifluoroethanol (TFE). This indicates that the ethylene bridge in 6-OTs does not significantly enhance the rate and that 6-OTs ionizes without anchimeric assistance. The solvolysis of [1-(13)C]-2-bicyclo[3.2.2]nonyl p-toluenesulfonate in methanol or TFE gave 2-substituted bicyclo[3.2.2]nonane, exo-2-substituted bicyclo[3.3.1]nonane, 2-bicyclo[3.2.2]nonene (10), and 2-bicyclo[3.3.1]nonene (11), whose distributions of (13)C labels were determined by quantitative (13)C NMR analysis using a relaxation reagent. The (13)C labels were exclusively placed at only two positions, the ratios of them were not unity, and the labels in 10 were less extensively scrambled than those in other products. These results indicate that the 2-bicyclo[3.2.2]nonyl cation is classical and that 10 is formed at a former ionization stage than 2-substituted bicyclo[3.2.2]nonane. The (13)C redistributions for both exo-2-substituted bicyclo[3.3.1]nonane and 11, which are yielded via 1,3-hydride shift, were similar to that of 2-substituted bicyclo[3.2.2]nonane, suggesting that 1,3-hydride shift occurs mainly at the solvent-separated ion pair.     

γ-anti-Effekt an 1-Phosphabicyclo[3.3.1]nonan-Derivaten mit Substituenten am Phosphor. Synthese und Struktur von Pentacarbonyl(1-phosphabicyclo[3.3.1]nonan)chrom

γ-Anti Effect in 1-Phosphabicyclo[3.3.1]nonane Derivatives with Substituents at Phosphorus. Synthesis and Structure of Pentacarbonyl(1-phosphabicyclo[3.3.1]nonane) Chromium In 1-phosphabicyclo[3.3.1]nonane derivatives of the composition C₈H₁₅P(X) the CC-conformation always dominates. Changes in the chemical shifts of the bridge-head carbon atom C(5) in the ¹³C-NMR spectrum are only originated by the electronic influence of the substituent X at the phosphorus centre. Based on a homogeneous interpretation of the electronic interactions and with regard to Pearsons's definition of electronegativity the electronegativities of substituents at the phosphorus atom X = Cr(CO)₅, Fe(CO)₄, and Ni(CO)₃ are estimated. These groups are placed in antiperiplanar orientation to the carbon atom C(5). The molecular structure of (1-phosphabicyclo[3.3.1]-nonane) Cr(CO)₅ 3 was elucidated by X-ray diffraction analysis. The molecule features the 1-phosphabicyclononane ligand in the CC-conformation, which has a nearly undistorted Cr(CO)₅ unit coordinated to the phosphorus atom (d Cr P = 2.368(1) Å).     

1H- und 13C-NMR-untersuchungen an dibromoxabicyclo[n.2.1]alkanen

The ¹H n.m.r. spectra of some dibromooxabicyclo[n.2.1]alkanes are discussed for the determination of the configuration and conformation. The ¹³C n.m.r. spectra confirm the observed stereochemistry. With increasing ring size the ¹³C n.m.r. chemical shifts of the hetero atom substituted C-atoms C-1 and C-2 move steadily to lower fields.     

Synthetic studies on phloroglucins: a new approach to the bicyclo[3.3.1]nonane system via the regioselective ring-opening of the methoxycyclopropane

A new synthetic approach to the bicyclo[3.3.1]nonane system, a common structure in a number of polyisoprenylated phloroglucinol derivatives (phloroglucins), has been developed. The key step in our approach is a ‘one-pot’ procedure of two successive reactions, the intramolecular cyclopropanation reaction which affords the tricyclo[4.4.0.0^5,7]dec-2-ene derivative and its methoxy group directed regioselective ring-opening reaction mediated by ZnCl₂, producing the desired bicyclo[3.3.1]nonane as the sole product.     

1H Nmr study of the preferred conformations in N-alkylgranatanine-3-spiro-5′-hydantoins

The conformations of a new series of compounds of the general structure N-alkylgranatanine-3-spiro-5′-hydantoin, synthesized in our laboratory from the corresponding 9-alkyl-9-azabieyclo-[3.3.1 ]nonan-3-ones, were studied by ¹ H nmr spectroscopy at different pH values in some instances. We have assigned boat conformations for the spiropiperidines.     

Simple NMR method for assigning relative stereochemistry of bridged bicyclo[3.n.1]-2-enes and tricyclo[7.n.1.0]-2-enes

The stereochemistry of syn and anti-forms of bridged bicyclo[3.n.1]-2-ene, tricyclo[7.n.1.0]-2-ene (n=1-3) and bicyclo[4.3.1]dec-7-ene derivatives can be assigned from the ¹³C chemical shift difference of the double bond. Both syn-9-R-bicyclo[3.3.1]non-2-enes and syn-13-R-tricyclo[7.3.1.0^2,7]tridec-2(7)-enes have a large shielding difference between sp² carbons, while the corresponding anti-forms have a smaller one. In contrast, 8-R-bicyclo[3.2.1]oct-2-enes and 12-R-tricyclo[7.2.1.0^2,7]dodec-2(7)-enes have an inverse correlation. The reason of this specificity is the influence of the γ-gauche effect on the chemical shift of C(2) atom. The GIAO theory has been applied to investigate the ¹³C chemical shifts. The conformational equilibrium in the formamide group of 13-formylamino-tricyclo[7.3.1.0^2,7]tridec-2(7)-enes has been studied.     

Stereochemical studies—XVIII : Conformational study of heteroanalogues of bicyclo[3.3.1]nonane

A number of heteroanalogues of bicyclo[3.3.1]nonane containing heteroatoms in 3-, 3,7- and 3,7,9-positions has been synthesized. ¹H NMR measurement has shown that the compounds of the types 4,5 and 6 (Y = oxygen) are double-chairs with the “wings” of the molecule flattened. However, a new conformational effect has been found for the sulfur containing compounds of type 5 and 6 (X,Y = sulfur) which show substantially increased tendency to adopt boat-chair conformations.     

Unusual carbon shielding effects of cyclopropanes and double bonds in strained bicyclo[3.1.0]hexanes and cyclopentenes

Carbon-13 shieldings and one-bond ¹³C? H coupling constants of bicyclo[2.1.1]hexane, bicyclo[2.1.1]hex-2-ene, tricyclo[3.1.1.0^2,4]heptane and benzvalene are presented and compared to the data of related compounds. If a bicyclo[3.1.0]hexane system is part of a rigid skeleton, the cyclopropane ring exerts specific γ substituent effects of two kinds. In the case of the bicyclohexane boat form an upfield shift of the C-3 signal is observed and in the case of the chair form a downfield shift of 15–20 ppm. Compared to the corresponding cyclopentanes the double bond in strained cyclopentenes causes downfield shifts of the C-4 absorption. This effect increases with increasing strain, reaching a 45.9 ppm maximum in benzvalene. Hence it is the only known bicyclo[1.1.0]butane having a reversed order of carbon shieldings. The downfield shifts are explained by means of simple orbital interaction schemes.     

Spectroscopic study of 3-methyl-2,4-diphenyl-3-azabicyclo[3.3.1]nonan-9-α(β)-ols

3-Methyl-2,4-diphenyl-3-azabicyclo[3.3.1]nonan-9-α(β)-ols have been synthesized and studied by ir, ¹H and ¹³C nmr spectroscopy. In deuteriochloroform and perdeuteriobenzene solutions, these compounds adopt a flattened chair-chair conformation in which the cyclohexane ring is more flattened. From the ¹H and ¹³C nmr data, several stereoelectronic effects have been deduced. The complete and unambiguous assignment of all protons of the 3-azabicyclo[3.3.1]nonane system, not described up to date, has been carried out.     

Organoboron compounds

Conclusions ³J_HH SSCC values and the¹³C chemical shifts of derivatives of 3-borabicyclo[3.3.1]nonane with a three-coordinated boron atom have a flattened double-chair conformation. The derivatives with a four-coordinated boron atom and a substituent at the 7 position have predominantly the chair-boat conformation, and the cyclohexane ring has the boat form; the the exceptions are the compounds with an internal donor-acceptor bond between boron and the 7 substituent.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 341–352, February, 1981.