Stereoelectronic effects in conformations of sulfide, sulfoxide, and sulfone α-carbanions

Süveges, Bastian D.; Podlech, Joachim

doi:10.1016/j.tet.2015.10.025

Cited by 6 publications

(5 citation statements)

References 70 publications

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“…During our investigations on sulfoxides − we obtained a number of 13 C NMR data and found these to be not fully consistent with the proposed γ-gauche effect (Chart , measured 13 C data are given in parentheses ,, ). To gain a deeper insight into this phenomenon we calculated chemical shifts for a wide selection of conformationally rigid thiane-derived sulfoxides together with data of substrates 1 – 3 , in which a rotation around S–C bonds is possible.…”

Section: Resultsmentioning

confidence: 94%

“… This γ-gauche effect has been investigated for different functional groups and this phenomenon is comprehensively described, though a general explanation has not been given. During our investigations on the influence of sulfoxide groups on structure, stability, reactivity, and spectroscopic properties of the respective compounds, − we realized that the γ-gauche effect in sulfoxides is not well understood and that a convincing and consistent explanation is still missing. It could be noted that the γ-gauche effect in sulfoxides actually occurs β to the SO group.…”

Section: Introductionmentioning

confidence: 99%

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Stereoelectronic Effects: The γ-Gauche Effect in Sulfoxides

Jung

Podlech

2018

J. Phys. Chem. A

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Reasons for the C NMR γ-gauche effect in sulfoxides, i.e., the distinct shielding of a carbon β to a gauche-oriented sulfoxide group were investigated. Several calculated and measuredC NMR data of open chain or thiane-derived sulfoxides revealed that an upfield shift is only observed for that γ-gauche position, in which the respective carbon is anti to the sulfoxide's sulfur lone pair. Carbons in γ-gauche position, which are synclinal to the lone pair, are not affected. The magnetic anisotropy of the S═O group was examined by generation of iso-chemical-shielding surfaces (ICSSs) and magnetically induced current maps. Stereoelectronic interactions were determined with natural bond orbital (NBO) and natural chemical shielding (NCS) analyses. The γ-gauche effect is best described by stereoelectronic interactions, especially those of the sulfur's lone pair with antibonding orbitals to a β-carbon in antiperiplanar orientation. An explanation based on steric interactions, which has frequently been referred to, is not suitable to describe the observed shielding effects. Furthermore, a description of the bonding situation in the S═O group is given. It can be understood as S-O triple bond, where the bond order is significantly reduced by antibonding contributions in some of the occupied molecular orbitals.

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Section: Resultsmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Stereoelectronic Effects: The γ-Gauche Effect in Sulfoxides

Jung

Podlech

2018

J. Phys. Chem. A

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“…The relevant equations are again given in the Supporting Information. MFH (4), tBuFH (5), and PhFH (7) were synthesized by slight modification of published protocols; 26,27 particularly, the purification processes were improved to obtain compounds of high purity (Scheme 1). The published synthesis of 9neopentylfluorene (NpFH, 6) required harsh conditions and gave low yields.…”

Section: T H Imentioning

confidence: 99%

“…During our continuous efforts in the investigation of stereoelectronic effects in sulfur-based functional groups, − we measured and calculated p K a values of thiane- and dithiane-derived sulfide, sulfoxide, and sulfone anions . Herein, we present a simple and general method for the measurement of p K a values of weakly C–H-acidic compounds.…”

mentioning

confidence: 99%

“…We have previously published calculated and provisional experimental p K a values for 1,3-dithiane dioxide isomers 1 – 3 to correlate these values with stereoelectronic effects operative in dithiane derivatives. − , p K a values of these compounds could be successfully determined with the new protocol. Identical p K a values for bissulfoxide 1 were determined with MFH and tBuFH as indicators.…”

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confidence: 99%

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Development of a Robust Protocol for the Determination of Weak Acids’ pK_a Values in DMSO

Jung

Podlech

2020

J. Org. Chem.

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Two methods for the determination of pK a values of weak acids are described, a direct titration with dimsyl potassium in the presence of an indicator and a back-titration in which an analyte/indicator mixture is deprotonated and then titrated with ammonium chloride. Both methods have been validated by measuring pK a values of compounds, for which values had been determined previously. The back-titration method was applied to measure pK a values of two 1,3-dithiane-derived bissulfoxides and a monosulfone.

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Stereoelectronic Effects: Perlin Effects in Thiane‐Derived Compounds

et al. 2020

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Stereoelectronic effects in thianes and thiane-derived sulfoxides, sulfones, sulfilimines, and sulfoximines were investigated by measuring 1 J C,H coupling constants and by identification of normal and reversed Perlin effects, i.e., of differences in the coupling constants for equatorial and axial C-H bonds in the methylene groups of six-membered rings. The Perlin effects were correlated with results from natural bond orbital (NBO) [a] Compounds 1-19 were used for NMR spectroscopic investigations, where 2,4-dimethyl-substituted compounds 17-19 were investigated for comparison. Only the sulfide 17, the equatorial sulfoxide 18, and the respective sulfone 19 were synthesized with this substitution pattern. The parent compounds 20-27 were used for calculations. Scheme 2. Synthesis of thiane 9. a) PhCHO, KOH, EtOH/H 2 O (78 %); b) O 3 , AcOH, 10°C, 5 h, then H 2 O 2 , reflux, 3 h; c) EtOH, cat. H 2 SO 4 , PhMe; Dean-Stark trap, 16 h (46 %); d) LiAlH 4 , Et 2 O, r.t., 16 h (93 %); e) MsCl, Et 3 N, CH 2 Cl 2 , r.t., 1 h (99 %); f) Na 2 S, EtOH/H 2 O, reflux, 2 h (78 %).Functionalization of thianes 1 and 9 was achieved with proven methods (Scheme 3). Oxidation with ozone yielded the equatorial sulfoxides 2 and 10, respectively, with good yields. [14] The axial sulfoxides (3 and 11) were obtained with a known protocol [14] by oxidation with tert-butyl hypochloride, albeit with quite poor yields. Excellent yields were observed in the preparation of sulfones 4 and 12, which was achieved with Eur. 2879 Scheme 4. Synthesis of 2,4-dimethylthiane derivatives. Conditions: a) MsCl, Et 3 N, CH 2 Cl 2 , 0°C, 45 min (quant.); b) Na 2 S, MeOH/H 2 O, reflux, 2 h (65 %); c) KMnO 4 , CH 2 Cl 2 /H 2 O, r.t., 16 h (94 %); d) BuLi, THF, 0°C to r.t., 30 min, then MeI, 0°C to r.t. (19: 17 %, 18: 30 %, diastereomerically pure); e) O 3 , CH 2 Cl 2 , -40°C to r.t., 2 h (67 %, d.r. = 5.8:1); f) P 4 S 10 , CDCl 3 .

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Stereoelectronic effects in conformations of sulfide, sulfoxide, and sulfone α-carbanions

Cited by 6 publications

References 70 publications

Stereoelectronic Effects: The γ-Gauche Effect in Sulfoxides

Stereoelectronic Effects: The γ-Gauche Effect in Sulfoxides

Development of a Robust Protocol for the Determination of Weak Acids’ pK_a Values in DMSO

Stereoelectronic Effects: Perlin Effects in Thiane‐Derived Compounds

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Stereoelectronic effects in conformations of sulfide, sulfoxide, and sulfone α-carbanions

Cited by 6 publications

References 70 publications

Stereoelectronic Effects: The γ-Gauche Effect in Sulfoxides

Stereoelectronic Effects: The γ-Gauche Effect in Sulfoxides

Development of a Robust Protocol for the Determination of Weak Acids’ pKa Values in DMSO

Stereoelectronic Effects: Perlin Effects in Thiane‐Derived Compounds

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Development of a Robust Protocol for the Determination of Weak Acids’ pK_a Values in DMSO