Conformational analysis 29: Preparation and1H and13C NMR, FTIR, MS, and crystallographic conformational and configurational study of 3-Oxo-1,3-oxathiane and its monomethyl derivatives

Pihlaja, Kalevi; Sillanpää, Reijo; Dahlqvist, Martti; Stájer, Géza; Ahlgrén, Markku

doi:10.1007/bf00679347

Cited by 14 publications

(9 citation statements)

References 28 publications

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“…1,3-Oxathiane 3-oxide ( 1 , Figure ) was computationally (B3LYP/aug-cc-pVDZ) found to be more stable in the SO ax conformation than in the SO eq form by 0.8 kcal mol –1 in the gas phase. The SO eq conformation agrees with the X-ray crystal structure of 2-phenyl-1,3-oxathiane 3-oxide but not with the more structurally similar compounds trans -5-methyl-3-oxo-1,3-oxathiane and (2 S C ,3 R S ,4 R C )-2-methyl-4-propyl-1,3-oxathiane 3-oxide (Figure ); other examples of the preferred gauche orientation along the OCSO fragment can be found in the Cambridge Structural Database (43 hits from the SOCH 2 O substructure). Actually, a more general representation of 1,3-oxathio 3-oxide compounds is the model (methoxymethyl)methyl sulfoxide (CH 3 SOCH 2 OCH 3 ); a conformational screening around the C–O–C–S and O–C–S–O dihedral angles gives the energy hypersurface of Figure , in which the global minimum A and a local minimum G correspond to gauche conformers relative to the O–C–S–O dihedral angle.…”

Section: Resultsmentioning

confidence: 58%

Simultaneous gauche and Anomeric Effects in α-Substituted Sulfoxides

Freitas

2012

J. Org. Chem.

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α-Substituted sulfoxides can experience both gauche and anomeric effects, since these compounds have the geometric requirements and strong electron donor and acceptor orbitals which are essential to make operative the hyperconjugative nature of these effects. Indeed, the title effects were calculated to take place for 1,3-oxathiane 3-oxide in polar solution, where dipolar effects are absent or at least minimized, while only the gauche effect is present in 2-fluorothiane 1-oxide. Since the fluorine atom is a suitable probe for structural analysis using NMR, the (1)J(CF) dependence on the rotation around the F-C-S═O dihedral angle of (fluoromethyl)methyl sulfoxide was evaluated; differently from 1,2-difluoroethane and fluoro(methoxy)methane, this coupling constant is at least not exclusively dependent on dipolar interactions (or on hyperconjugation). Because of the nonmonotonic behavior of the (1)J(CF) rotational profile, this coupling constant does not appear to be of significant diagnostic value for probing the conformations of α-fluoro sulfoxides.

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Section: Resultsmentioning

confidence: 58%

Simultaneous gauche and Anomeric Effects in α-Substituted Sulfoxides

Freitas

2012

J. Org. Chem.

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“…This should be the case if the heterocyclic ring in the a series is in an almost perfect chair form and the b isomers display some distortion or exist in conformational equilibrium. The values for geminal coupling between H-4eq and H-4ax (ranging from −11.0 to −11.2 Hz, see Table ) in the trans-fused a forms indicate that the substituent on the ring nitrogen is in the equatorial position 6 Possible heteroring conformations for the trans-fused isomers. 4 Selected Geminal and Vicinal H, H Coupling Constants (Hz) a 4ax,4eq4a,4ax4a,4eq4a,5ax4a,5eq4a,8a5ax,5eq5ax,6ax5ax,6eq8ax,8eq8a,8ax8a,8eq 1a −11.0 10.8 4.5 12.5 <3 10.4 −12.5 12.5 4.1 −12 11 4.4 1b −12.8 11.1 4.5 11 4 9.4 −13.5 12.5 4.0 −12.7 11.1 4.4 2a −11.6 3.9 2.0 12.2 3.9 3.9 2b −13.1 3.9 3.5 11.2 3.7 2.6 −13.4 11.2 3.5 −13.6 5.1 2.6 3a −11.0 11.3 4.6 12.810.2 −12.8 12.8 10.2 4.3 3b −11.13 11.16 5.26 12.6 3.1 10.7 −12.6 12.6 3.7 −12.8 11 4.5 4a −11.5 3.7 1.7 12.5 3.7 3.7 −12.6 12.6 3.7 −10.9 3.2 4b −11.6 4.9 7.6 4.1 4.6 3.9 −13.6 −13.5 3.9 8.9 5a −11.2 11.2 4.6 12.8 10.56 −12.8

…”

Section: Resultsmentioning

confidence: 99%

“…In the b series, the more negative values for the geminal 2 J (H4eq,H4ax) coupling (Table ) shows that R 1 displays some tendency to occupy an axial position …”

Section: Resultsmentioning

confidence: 99%

Conformational Study of Some Saturated 2-[Bis(2-chloroethyl)amino]-1,3,2-benzoxazaphosphorinane 2-Oxides

et al. 1998

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Conformational analyses of cis- and trans-fused 2-[bis(2-chloroethyl)amino]-3,4,4a,5,6,7,8,8a-octahydro-1,3,2-benzoxazaphosphorinane 2-oxides and their 3-methyl and 3-benzyl derivatives were performed by (1)H, (13)C, (31)P, and variable-temperature NMR methods. Depending on the P-2 configuration and the substituent on N-3, different equilibria between chair-chair and chair-twist-boat conformations were found for the trans-fused isomers. The N-3 substituent shifts the equilibrium toward the chair-twist-boat to an extent varying in the sequence methyl > benzyl > hydrogen. In the cis-fused isomers, the nature of the N-3 substituent affects the equilibrium between the O-in and O-out conformations in the same sequence.

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“…Since we studied earlier conformations of 3‐oxo‐1,3‐oxathiolanes11 and 3‐oxo‐1,3‐oxathianes,12 we decided to synthesize several 1‐oxo‐1,3‐dithiolanes ( 4 – 10 ; Scheme ) from the corresponding 1,3‐dithiolanes13 ( 1–3 ; Scheme ) and elucidate their structures with the aid of their NMR spectra and computational results (Figure 1).…”

Section: Introductionmentioning

confidence: 68%

1‐Oxo‐1,3‐dithiolanes—synthesis and stereochemistry

Pihlaja

Sinkkonen

Stájer

et al. 2011

Magnetic Reson in Chemistry

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1-Oxo-1,3-dithiolane (4) and its cis- and trans-2-methyl (5,6), -4-methyl (7,8) and -5-methyl (9,10) derivatives were prepared by oxidizing the corresponding 1,3-dithiolanes (1-3) with NaIO(4) in water. The oxides were purified and their isomers separated using thin layer chromatography. The structural characterization was carried out with (1)H and (13)C NMR spectroscopy and molecular modelling. The sulfoxides 4-6 and 8-10 attain two S(1) type envelopes (sometimes slightly distorted) the S=O(ax) envelope greatly dominating. Cis-4-methyl-1-oxo-1,3-dithiolane is a special case exhibiting both two closely related S=O(ax) (30 and 27%) as well as S=O(eq) (21 and 22%) forms [S(1) and C(4) envelopes, respectively]. The relative energies of these conformations, the values of (1)H-(1)H coupling constants and (1)H and (13)C chemical shifts were estimated by computational methods and they support well the conclusions based on the experimental data.

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Conformational analysis 29: Preparation and1H and13C NMR, FTIR, MS, and crystallographic conformational and configurational study of 3-Oxo-1,3-oxathiane and its monomethyl derivatives

Cited by 14 publications

References 28 publications

Simultaneous gauche and Anomeric Effects in α-Substituted Sulfoxides

Simultaneous gauche and Anomeric Effects in α-Substituted Sulfoxides

Conformational Study of Some Saturated 2-[Bis(2-chloroethyl)amino]-1,3,2-benzoxazaphosphorinane 2-Oxides

1‐Oxo‐1,3‐dithiolanes—synthesis and stereochemistry

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