nmr and quantum-chemical study of the stereochemistry of spiroepoxides obtained by oxidation of...

MAGNETIC RESONANCE IN CHEMISTRYMagn. Reson. Chem. 2001; 39: 251–258

NMR and quantum-chemical study of thestereochemistry of spiroepoxides obtained by oxidationof (Z)-3-arylidene-1-thioflavan-4-ones†

Gabor Toth,1∗ Jozsef Kovacs,1 Albert Levai,2 Erich Kleinpeter3 and Andreas Koch3

1 Technical Analytical Research Group of the Hungarian Academy of Sciences, Institute for General and Analytical Chemistry, Technical University ofBudapest, Szent Gellert ter 4, H-1111 Budapest, Hungary2 Department of Organic Chemistry, Debrecen University, P.O. Box 20, H-4010 Debrecen, Hungary3 Universitat Potsdam, Institut fur Organische Chemie und Strukturanalytik, P.O. Box 691553, D-14415 Potsdam, Germany

Received 29 September 2000; Revised 19 January 2001; Accepted 22 January 2001

Epoxidation of (Z)-3-arylidene-1-thioflavan-4-ones (1) yielded trans,cis (2) and trans,trans (3) isomers. Thestructure and signal assignments were elucidated by extensive application of one- and two-dimensional1H and 13C NMR spectroscopy. The conformational analysis was achieved by the application of 3J(C,H)couplings and ab initio MO calculations. Both the preferred ground-state conformers (envelope-Aconformations) obtained as global minima of the HF ab initio structures and the 13C chemical shiftscalculated by the GIAO method from the global minima structures of the trans,cis and trans,trans isomersare in agreement with the experimentally obtained NMR results. Copyright 2001 John Wiley & Sons,Ltd.

KEYWORDS: NMR; 1H NMR; 13C NMR; spiroepoxides, long-range 3J(C,H) couplings, conformational analysis; ab initio MOstudy

INTRODUCTION

We have recently reported on the stereoselective epoxidationof exocyclic ˛,ˇ-unsaturated ketones including 2-arylidene-1-tetralones,1 -1-indanones2,3 and -1-benzosuberones,2,3 3-arylidenechromanones4 and 3-arylideneflavanones5 by di-methyldioxirane. Unfortunately, this convenient oxidizingagent proved to be inadequate for the epoxidation of 3-arylidene-1-thioflavan-4-ones; only sulfoxides or sulfoneswere obtained depending on the amount of the oxidant,instead of epoxides.6 For this reason, we have now con-ducted the epoxidation of (Z)-3-arylidene-1-thioflavan-4-ones using nucleophilic oxidants, viz. alkaline hydrogen per-oxide (Weitz–Scheffer reaction) and sodium hypochlorite. Inprinciple, these procedures may provide four diastereomericspiroepoxides, namely the trans,cis (2), trans,trans (3), cis,cis(4) and cis,trans (5) isomers. The first prefix refers to the rela-tive position of the carbonyl and the aryl groups of the epox-ide ring, and the second prefix describes the relative positionof the phenyl group at C-2 and the epoxide oxygen connectedto the C-3 atom. All of these compounds are racemates.

ŁCorrespondence to: G. Toth, Technical and Analytical ResearchGroup of the Hungarian Academy of Sciences, Institute for Generaland Analytical Chemistry, Technical University of Budapest, SzentGellert ter 4, H-1111 Budapest, Hungary. E-mail: [email protected]†This paper is dedicated to Prof. Dr Laszlo-Szilagyi on the occasionof his 60th birthday.Contract/grant sponsor: Hungarian Scientific Research Fund;Contract/grant number: OTKA T026264; OTKA T029171.

RESULTS AND DISCUSSION

The oxidation reactions of the (Z)-3-arylidene-1-thioflavan-4-ones (1) always yielded two diastereomers (2 and 3) inratios of ca 3 : 2 (Scheme 1). The separation of diastereomerswas achieved by column chromatography.7 Beirne andO’Sullivan also obtained a mixture of two isomers from(Z)-3-benzyliden-6-methyl-1-thioflavan-4-ones on treatmentwith alkaline hydrogen peroxide or sodium hypochlorite.8

Complete 1H and 13C NMR signal assignments wereachieved using gs-COSY, gs-HSQC and gs-HMBC measure-ments. The chemical shifts of 2 and 3 are summarized inTables 1 and 2. The 13C-coupled HSQC measurement notonly proved to be very powerful for the assignment of thedirect coupled carbon–proton pairs but also allowed the dif-ferentiation between the methine groups in positions 2 and30. It is well known9,10 that the value of the one-bond CH cou-pling constant of epoxides is extremely high, around 180 Hz.The cross peaks at 5.3/64 and 4.4/65 ppm for 2 and 3 showa 1J(C,H) coupling of 180–183 Hz, unambiguously provingthe existence of the oxirane ring and allowing differentiationof the C-2 and C-30 methine groups.

For the evaluation of the interprotonic proximities, wemeasured selective 1D NOESY and phase-sensitive 2DNOESY spectra. These revealed that H-2 and the aryl groupat C-30 are in spatial proximity in the products 2 and 3,whereas no NOE responses were observed among H-30/H-2and H-30/H-200, 600 protons. These observations support thetrans,cis and trans,trans type of structures of the products

DOI: 10.1002/mrc.840 Copyright 2001 John Wiley & Sons, Ltd.

252 G. Toth et al.

Scheme 1. Reaction route.

Table 1. 1H chemical shifts (ppm) of 2 and 3 (in CDCl3)

2a 2b 2c 2d 2e 2f 3a 3b 3c 3d 3e 3f

2 3.96 3.98 3.98 3.88 3.93 3.86 4.22 4.26 4.20 4.17 4.11 4.1930 4.43 4.40 4.38 4.38 4.52 4.53 5.33 5.33 5.27 5.28 5.48 5.455 8.09 8.09 8.08 8.06 8.10 8.10 8.09 8.09 8.04 8.10 8.09 8.146 7.20 7.19 7.17 7.19 7.19 7.20 7.21 7.21 7.18 7.23 7.20 7.257 7.40 7.39 7.37 7.40 7.39 7.40 7.42 7.41 7.39 7.43 7.39 7.438 7.22 7.22 7.21 7.22 7.22 7.24 7.29 7.30 7.26 7.29 7.25 7.292C 7.54 7.42 7.45 7.51 — — 7.37 7.28 7.26 7.38 — —3C 7.44 7.25 6.96 7.13 6.97 7.47 7.31 7.14 6.83 7.00 6.68 7.274C 7.44 — — — 7.39 7.38 7.32 — — — 7.25 7.245C 7.44 7.25 6.96 7.13 7.00 7.35 7.31 7.14 6.83 7.00 6.96 7.246C 7.54 7.42 7.45 7.51 7.38 7.50 7.37 7.28 7.26 7.38 7.37 7.41Me — 2.41 — — 3.82 — — 2.34 — — 3.61 —200,600 7.52 7.52 7.52 7.49 7.50 7.50 6.98 7.05 7.00 6.99 7.05 7.00300,500 7.25 7.24 7.25 7.25 7.25 7.25 7.07 7.11 7.06 7.09 7.05 7.07400 7.23 7.22 7.22 7.23 7.23 7.25 7.11 7.09 7.09 7.13 7.05 7.13

Table 2. 13C chemical shifts (ppm) of 2 and 3 (in CDCl3)

2a 2b 2c 2d 2e 2f 3a 3b 3c 3d 3e 3f

2 45.2 45.2 45.2 45.2 45.1 45.1 46.5 46.4 46.4 46.6 47.0 47.13 66.7 66.7 65.7 66.6 66.6 66.7 64.2 64.2 64.1 64.0 63.5 64.130 65.6 65.7 65.5 65.0 63.2 64.0 64.0 64.1 63.9 63.5 61.8 62.74 190.2 190.3 190.3 190.0 190.5 189.7 189.4 189.4 189.6 189.3 189.7 188.94a 132.0 132.0 131.9 132.0 132.1 131.8 131.1 131.1 131.2 131.1 131.5 131.25 129.4 129.3 129.2 129.4 129.3 129.4 129.8 129.7 129.7 129.8 129.7 129.96 125.9 125.8 125.8 126.0 127.4 125.8 125.9 125.8 125.8 126.0 125.9 126.07 134.6 134.5 134.5 134.7 134.4 134.6 134.6 134.5 134.5 134.7 134.4 134.68 128.2 128.2 128.1 128.2 128.1 128.2 128.6 128.2 128.2 128.3 128.5 128.38a 138.1 138.1 138.0 137.9 138.5 138.4 139.9 139.9 139.9 139.7 139.5 139.71C 133.6 130.5 125.4 129.3 122.4 131.7 133.4 130.3 125.3 129.2 122.0 131.62C 127.1 127.0 128.3 128.9 159.0 134.5 126.8 126.7 128.0 128.5 158.1 134.03C 128.8 129.3 114.0 115.8 110.8 129.8 128.5 129.2 114.0 115.6 110.0 126.84C 129.2 139.0 160.2 163.2 130.2 130.3 128.5 138.4 159.9 162.9 129.7 129.75C 128.8 129.3 114.0 115.8 120.4 126.9 128.5 129.2 114.0 115.6 120.3 129.56C 127.1 127.0 128.3 128.9 127.4 128.1 126.8 126.7 128.0 128.5 127.1 127.8Me — 21.5 55.4 — 55.7 — — 21.4 55.4 — 55.0 —100 136.8 136.9 136.9 136.6 137.3 136.7 136.5 136.4 136.5 136.5 137.1 136.4200,600 128.1 128.1 128.0 128.1 128.2 128.1 127.6 127.7 127.6 127.5 127.6 127.5300,500 128.7 128.7 128.7 128.8 128.7 128.8 128.2 128.5 128.5 128.6 128.2 128.5400 128.1 128.1 128.0 128.2 128.0 128.1 128.1 128.0 128.0 128.1 127.7 128.1

Copyright 2001 John Wiley & Sons, Ltd. Magn. Reson. Chem. 2001; 39: 251–258

Stereochemistry of spiroepoxides 253

and the cis,cis and cis,trans structures can be ruled out. All ofthese are in accordance with the epoxidation of the analogousflavanones, e.g. the configuration of the exo-double bond isretained during the oxidation.11,12

The elucidation of the stereochemistry and relativeconfiguration of the spiroepoxides was difficult owing to theequilibrium among boat-A ↼⇁ envelope-A ↼⇁ envelope-B ↼⇁boat-B conformers (Scheme 2), as can be seen by inspectingthe Dreiding stereomodel.5 Inversion of the hetero ring isconnected with the interconversion of the quasi-axial (A) andquasi-equatorial (B) arrangements of the 2-phenyl group andthe oxygen atom of the epoxide. It has been found previouslythat the vicinal H-2 and C-8a coupling constant wasindicative of the steric position of the phenyl-2 group.4,5,13,14

Scheme 2. Conformational equilibrium of trans,trans-3.

The value of ca 8 Hz corresponds to a ca 180° dihedralangle between equatorial H-2 and C-8a, while the couplingconstant of ca 1 Hz derives from an 80° angle between theaxial H-2 and C-8a atoms. For the determination of thesecoupling constants we applied 1H detected 1D gradient-selected long-range 13C,1 H correlation,15,16 2D INAPT17 andGSQMBC18 experiments. All of these methods provided thesame value of the coupling constant 3J�H-2,C-8a� D 7.6 Hz asdepicted for 2c [Fig. 1(a)–(c)]. Comparing the three differenttype of measurements, GSQMBC is the most powerful,providing all long-range nJ�C,H� coupling constants in oneexperiment with a moderate time requirement. The accuracyof the determination of nJ�C,H� coupling constants is limitedby the size of F2 in the data matrix. In this respect the inversedetected 1D gradient-selected long-range 13C, 1H correlationexperiment is better, but results only in the coupling ofprotons to one selected carbon atom. Evaluation of the exactvalue of coupling constants becomes difficult in the caseof proton signals with high multiplicity. The 2D INAPTexperiment does not suffer from this problem; the signalsobserved are always doublets, and the accuracy depends onthe size of F1 of the data matrix. Owing to the 13C detection thesensitivity is moderate, but in the case of high concentrationsthe time requirement can be low.

The measured values of 3J�H-2,C-8a� D 7.0–7.8 Hz for 2and 3 support the quasi-axial position of the Ph—C-2 group,i.e. the envelope-A is the preferred conformer. This result

is strongly corroborated by the ab initio calculations; in theglobal minima conformers of trans,cis and trans,trans isomersthe dihedral angles C-8a—S—C-2—H-2 found are less than180° but 153.9–170.4° (cf. Table 3) in coincidence with thesecharacteristic long-range nJ�C,H� coupling constants com-piled in Table 4. In conformers boat-A and envelope-B thisdihedral angle is expected to be ca 60° –80°, whereas in thecase of boat-B it should be ca 150–160°. The MO calcula-tions identified envelope-B as the second stable conformerof the trans,cis and trans,trans isomers; the dihedral angles C-8a—S—C-2—H-2 in the global minima structures proved tobe 56–61°. The two boat conformers could not be located aslocal/global energy minima structures in the trans,cis (2) andtrans,trans (3) isomers according to the present ab initio MOcalculations. The relative energy calculated for the 16 pre-ferred conformers of the isomers/enantiomers of 2a–5a andthe corresponding dihedral angles are compiled in Table 3.In Scheme 3, only the energetically most preferred conform-ers are depicted for the trans,cis and trans,trans isomers,respectively (enantiomers with R configuration at C-2).

A common characteristic of the 1H NMR spectra of2 and 3 is the extremely high chemical shift of the H-5 signals as a consequence of the well-known anisotropiceffect of the peri-positioned C-4 O carbonyl group. Inthe two boat conformers, the angle between the planes ofthe carbonyl group and the condensed aromatic ring is ca20–30°. Comparing the chemical shifts of H-5 measured inflavanones and 1-thioflavan-4-ones,19 a 0.2 ppm downfieldshift was observed for the thio analogues. On this basis wecan conclude that the measured υH-5 D 8.04–8.14 valuesfor 2 and 3 compared with those observed previously forthe analogous flavanone spiroepoxides5 �υ D 7.84–7.94� alsosupport the predominance of the envelope-A conformer.The corresponding dihedral angles O C-4—C-4a—C-5, ascalculated in the present ab initio MO study, also indicate themore or less in-plane position of the C-4 carbonyl group andthe condensed aromatic ring (2.3–8.5°; cf. Table 3). However,a similar dihedral angle was calculated for the envelope-Bconformer of the trans,trans isomer �3.4°�. For the boat-Aconformer of the trans,cis isomer, as expected, a larger twistbetween the two moieties was found �23.3°�.

For the elucidation of the trans and cis orientation of theepoxy oxygen atom with respect to the C-2 phenyl group,the chemical shift value of the H-30 proton was utilized.In a trans,trans compound C-30 is quasi-equatorial for thesix-membered ring and, therefore, the H-30 proton is locatedclose to the C-4 O group and approximately coplanar withit, resulting in υ D 5.27–5.45 ppm chemical shifts. In the caseof the trans,cis isomer, the H-30 proton is below the plane ofthe carbonyl group and the dihedral angle is about 35°, sothat the effect of the peri carbonyl group is weaker and thechemical shifts are υ D 4.38–4.53 ppm. For the calculation ofmagnetic shielding of the C-4 O group, H2C O was usedas a model and grid points in the surrounding lead to theanisotropic effect, as depicted in Fig. 2. The grid is defined byan x,y,z range from �10 to 10 A and the grid spacing is 0.5 A.The contour level is 0.4 ppm (dark grey) and �0.4 ppm (lightgrey). On this basis, it is easy to explain the 0.8 ppm upfieldshift of the H-30 signals in compounds 2 compared with 3.


254 G. Toth et al.

Figure 1. Determination of the 3J(C-8a,H-2) coupling constant by (a) 1H detected 1D gradient-selected long-range 13C,1 Hcorrelation, (b) 2D INEPT and (c) GSQMBC experiments.



Tab

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312

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.53a

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.-A6.

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.9�2

.93a

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.49

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.640

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.-A3.

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.83.

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.97.

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2


256 G. Toth et al.

Table 4. Characteristic 3J(C,H) coupling constants of 2 and3 (Hz)

2b 2c 2e 2f 3b 3c 3e 3f

3J(C-8a,H-2) 7.6 7.6 7.5 7.5 7.3 7.0 7.2 7.03J(C-200,600,H-2) 3.8 3.4 3.4 2.8 3.5 3.7 4.0 4.13J(C-2C,6C,H-30) 4.1 2.9 2.1, 2.7 1.9, 3.5 2.5 1.8 2.1, 4.0 3.0

Scheme 3. Computed stereochemistry of the preferred con-formers.

The conformational characteristics of the phenyl groupsconnected to the C-2 and C-30 atoms could be assessed on thebasis of the 3J�H-2, C-200, 600� and 3J�H-30,C-2C, 6C� couplingconstants. If the C—H bond and the connecting aromaticring are coplanar, the coupling constant is 5–6 Hz, whichdecreases gradually together with the decrease in the ratioof this conformer.5,13,14 On the basis of the measured values(e.g. 2b, 4.1 Hz; 3b, 2.5 Hz), the populations of conformersalong the C—C(aryl) axis are almost the same and nopreferred rotamers were identified, which is also indicatedby the dihedral angles obtained by the ab initio MO study(Table 3).

It is worth mentioning that, in the trans,trans isomer,the ortho-protons of the phenyl—C-2 are shielded �υ D6.98–7.05�. This change in chemical shifts can be explainedby considering the location of these protons in the shielding

Figure 3. Ortho-protons of C-2—phenyl positioned in the�0.3 ppm shielding area of the C-30 —phenyl anisotropy cone.

area (�0.3 ppm) of the C-30 —phenyl anisotropy cone, as canbe seen in Fig. 3.

The structures and stereochemistry of the preferredconformers of spiroepoxides 2 and 3 obtained from theNMR investigations are in accordance with the results ofthe ab initio calculations. The relative energies of trans,cis,trans,trans, cis,cis and cis,trans spiroepoxides are compiled inTable 3. Considering the comparable relative energies of thepreferred conformers of the four spiroepoxide isomers, wecan conclude that the epoxidation is ruled by kinetic control,resulting in only trans,cis (2) and trans,trans (3) isomers.

In a few cases, small energy differences between thepreferred conformers of enantiomers, belonging together,were calculated. This reflects different local minima for therotation of both the C-2 and C-30 phenyl rings in the preferredconformers (see Table 3, e.g. RRS and SSR of 2a as depicted inScheme 4). The axial orientation of the 2-Ph group (envelope-A conformation) is preferred over the second lowest energyconformation (boat-A in the case of 2 and envelope-B in thecase of 3) by ca 17 and 14 kJ mol�1, respectively.

The applicability of the employed quantum chemicalMO calculations for the present compounds can be simplyverified by calculating their 13C chemical shifts on the

Figure 2. Anisotropic effect of the carbonyl group.



Scheme 4. Stereo pictures of the lowest energy conformationresulted from ab inito MO calculation for the RRS and SSRenantiomers of 2a.

basis of the structures obtained. The conformity of thecorresponding calculated and experimental values provesboth to be a guarantee of the correctness of the theoreticallevel selected and of the electron densities thus calculated,which are most important for the magnetic shieldings. Thecomparison of the calculated 13C chemical shifts for the moststable conformers of (a) 2a and (b) 3a with the measureddata are shown in Fig. 4. It should be mentioned that,despite the good correlation between the experimental andcalculated 13C chemical shifts, the elucidation of the structureof spiroepoxide isomers on the basis of these data alone isnot possible, because the experimental 13C chemical shiftdifferences of the corresponding carbon atoms in the isomers2 and 3 are small, corroborating the importance of NOESYand 3J�C,H� data. However, the theoretical level used forthe present calculations proved to be sufficient to establishthe conformations and relative energetic stabilities of thethioflavanones studied.

Figure 4. Comparison of the calculated 13C chemical shifts forthe most stable conformers of (a) 2a and (b) 3a with themeasured data.

EXPERIMENTAL

CompoundsThe synthesis of 2 and 3 was published separately.7

NMR measurementsNMR spectra were recorded in chloroform-d at room tem-perature using a Bruker Avance DRX-500 spectrometer.Chemical shifts are given on the υ-scale and were refer-enced to the solvent. In the 1D measurements (1H, 13C,NOESY), 32K data points were acquired and zero-filled upto 64K.

The pulse programs of the gs-COSY, 1D-gs-NOESY,NOESY, gs-HSQC and gs-HMBC experiments were takenfrom the Bruker software library, and the parameters wereas the same as described before.16,17.

1H detected 1D gradient-selected long-range 13C, 1Hcorrelation15,16 optimized for 9 Hz 13C, 1H coupling constantunder decoupling of C-8a, C-200,600 and C-2C6C, respectively;90° pulse 9.6 µs for 1H, 11.8 µs for 13C hard pulses andP11 D 20 ms selective 90° Gaussian 13C pulse on thepower level of 56.8 dB, relaxation delay D1 D 1.5 s, delayfor evolution of long-range couplings (9 Hz) D6 D 18 ms,gradient program 2sine, gradient ratio 80 : 20.

For 2D semi-selective INEPT17 spectra: relaxation delayD1 D 1.5 s, delay for evolution of long-range coupling inexperiment (a) D2 D 23 ms (J D 7.5 Hz), evolution delayD3 D 28 ms, and in experiment (b) D2 D 73 ms (J D 3 Hz),evolution delay D3 D 78 ms, 90° pulse 9.6 µs for 1H, 11.8 µsfor 13C hard pulses, 1K points in t2, sweep width 16 Hz inF1 and 160 ppm in F2, 16 experiments in t1, linear predictionto 32 and zero-filling up to 64 real points in F1, apodizationwith a /2-shifted squared sine-bell in F1 and sine-bell in F2

dimensions, respectively.For the gradient-enhanced single quantum multiple

bond correlation (GSQMBC)18 experiment: relaxation delayD1 D 2.5 s, 90° pulse 9.6 µs for 1H, 11.8 µs for 13C hardpulses, 2K points in t2, sweep width 6.5 ppm in F2 and190 ppm in F1, 256 experiments in t1, linear prediction to512 and zero-filling up to 1K real points in F1, apodizationwith a /2-shifted squared sine-bell in F1 and sine-bell in F2

dimensions, respectively.

Ab initio calculationsAb initio calculations were carried out with the Gaussian98 and Gaussian 94 programs20,21 using the 6–31GŁ basisset22 at the Hartree–Fock level. Geometry optimizationsof all configurations were performed without constraints.NMR chemical shifts were calculated using the ‘gaugeincluding’ atomic orbital GIAO method.23 The 13C chemicalshifts are differences in the magnetic shielding of thecarbon atoms and the carbons of TMS as the reference.The results were visualized using the program SYBYL 6.6.24

The quantum chemical calculations were processed on SGIOctane (R 12000) and SGI Origin (24 R 10000) computers atPotsdam University.

AcknowledgementThis project was supported by the Hungarian Scientific ResearchFund (OTKA T026264 and T029171).


258 G. Toth et al.

REFERENCES1. Adam W, Halasz J, Jambor Zs, Levai A, Nemes Cs, Patonay T,

Toth G. J. Chem. Soc., Perkin Trans 1 1996; 395.2. Toth G, Halasz J, Boros S, Levai A, Nemes Cs, Patonay T. Magn.

Reson. Chem. 1996; 34: 932.3. Halasz J, Toth G, Levai A, Nemes Cs, Jambor Zs. J. Chem. Res.

(S) 1994; 326.4. Adam W, Halasz J, Levai A, Nemes Cs, Toth G. Liebigs Ann.

Chem. 1994; 795.5. Nemes Cs, Levai A, Patonay T, Toth G, Boros S, Halasz J,

Adam W, Golsch D. J. Org. Chem. 1994; 59: 900.6. Adam W, Golsch D, Hadjaiarapoglou L, Levai A, Nemes Cs,

Patonay T. Tetrahedron 1994; 50: 13113.7. Levai A, Patonay T, Vass EB, Toth G, Kovacs J. Monatsch. Chem.

2001; 132: in press.8. Beirne JJ, O’Sullivan WI. Proc. R. Ir. Acad., Sect. B 1977; 77:

337.9. Breitmayer E, Voelter W. Carbon-13 NMR Spectroscopy (3rd edn).

VCH: Weinheim, 1987; 288.10. Kalinowski H-O, Berger S, Braun S. 13C NMR Spektroskopie.

Georg Thieme: Stuttgart, 1984.11. Keane DD, O’Sullivan WI, Philbin EM. Tetrahedron 1970; 26:

2533.12. Keane DD, O’Sullivan WI, Philbin EM. Tetrahedron 1971; 27:

3535.13. Toth G, Szollosy A, Levai A, Oszbach Gy, Dietrich W, Kuhne H.

Magn. Reson. Chem. 1991; 29: 801.14. Toth G, Levai A, Szollosy A, Duddeck H. Tetrahedron 1993; 49:

863.15. Stelten J, Leibfritz D. Magn. Reson. Chem. 1995; 33: 827.

16. Okogun JI, Duddeck H, Habermehl G, Krebs HC, Toth G,Simon A. Magn. Reson. Chem. 1998; 36: 371.

17. Jippo T, Kamo O, Nagayama K. J. Magn. Reson. 1986; 66: 344.18. Marek R, Kralik L, Sklenar V. Tetrahedron Lett. 1997; 33: 665.19. Levai A, Szollosy A, Toth G. Acta Chim. Hung. 1991; 128:

359.20. Frisch MJ, Trucks GW, Schlegel HB, Scuseria GE, Robb MA,

Cheesman JR, Zakrewski VG, Montgomery Jr JA, Stratmann RE,Burant JC, Dapprich S, Millam JM, Daniels AD, Kudin KN,Strain MC, Farkas O, Tomasi J, Barone V, Cossi M, Cammi R,Mennucci B, Pomelli C, Adamo C, Morokuma K, Malick DK,Rabuck AD, Raghavachari K, Foresman JB, Cioslowski J, OrtizJV, Babaoul AG, Stefanov BB, Liu G, Liashenko A, Piskorz P,Komaromi I, Gomperts R, Martin RL, Fox DJ, Keith T, Al-Laham MA, Peng CY, Nanayakkara A, Gonzalez C, Challa-combe M, Gill PMW, Johnson B, Chen W, Wong MW, Andres JL,Gonzalez C, Head-Gordon M, Replogle ES, Pople JA. Gaussian98. Gaussian: Pittsburgh, PA, 1998.

21. Frisch MJ, Trucks GW, Schlegel HB, Gill PMW, Johnson BG,Robb MA, Cheesman JR, Keith T, Petterson GA, MontgomeryJA, Raghavachari K, Al-Laham MA, Zakrewski VG, Ortiz JV,Foresman JB, Cioslowski J, Stefanov BB, Nanayakkara A, Chal-lacombe M, Peng CY, Ayala PY, Chen W, Wong MW, Andres JL,Replogle ES, Gomperts R, Martin RL, Fox DJ, Binkley JS, DefreesDJ, Baker J, Stewart JP, Head-Gordon M, Gonzalez C, Pople JA.Gaussian 94. Gaussian: Pittsburg, PA, 1995.

22. Hehre WJ, Radom L, Schleyer PvR, Pople JA. Ab-initio MolecularOrbital Theory. Wiley: New York, 1986.

23. Ditchfield R. Mol. Phys. 1974; 27: 789.24. SYBYL 6.6. Tripos: St. Louis, MO, USA, 1999.


nmr and quantum-chemical study of the stereochemistry of spiroepoxides obtained by oxidation of...

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