Flavanoid epoxides—VI

Keane, D.; O'Sullivan, W. Ivo; Philbin, E. M.; Simons, R.M.; Teague, Peyton C.

doi:10.1016/s0040-4020(01)92828-5

Cited by 12 publications

(10 citation statements)

References 26 publications

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“…3-Arylideneflavanones (also termed flavindogenides) are well-known exocyclic α,β-unsaturated ketones. Their synthesis and chemical transformations were thoroughly investigated by several research groups [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. However, the related 3-arylidene-1-thioflavanones have hitherto received less attention.…”

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confidence: 99%

Dimethyldioxirane oxidation of the epoxides of (Z)‐3‐arylidene‐1‐thioflavanones

Lévai

Patonay

Tóth

et al. 2002

Journal of Heterocyclic Chem

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Dedicated to Professor Dr. Waldemar Adam on the occasion of his 65 th birthday.Sulfur atom of the trans,cis-and trans,trans-epoxides 1 of (Z)-3-arylidene-1-thioflavanones have been oxidized with dimethyldioxirane to afford the appropriate sulfoxides 2 and sulfones 3 depending on the amount of oxidant used.J. Heterocyclic Chem., 39, 817 (2002). 3-Arylideneflavanones (also termed flavindogenides) are well-known exocyclic α,β-unsaturated ketones. Their synthesis and chemical transformations were thoroughly investigated by several research groups [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. However, the related 3-arylidene-1-thioflavanones have hitherto received less attention. (Z)-3-Arylidene-1-thioflavanones, where the carbonyl and aryl moieties are on opposite sides of the carbon-carbon double bond, were obtained by acid- [15][16][17] and base-catalyzed condensation [18] of 1-thioflavanones and aromatic aldehydes. Their (E)-isomers, where the aryl and carbonyl groups are on the same side of the carbon-carbon double bond were prepared by the photoisomerization of the appropriate (Z)-3-arylidene-1-thioflavanones [19,20]. Previously, we have studied several chemical transformations of the 3-arylidene-1-thioflavanones including their oxidation with dioxiranes [10,[21][22][23][24][25][26].It has been found that, depending on the amount of the oxidant, dimethyldioxirane oxidation of (Z)-3-arylidene-1-thioflavanones afforded sulfoxides and/or sulfones which could not be epoxidized to their corresponding epoxides either with a high excess of dimethyldioxirane or with the much more effective methyl(trifluoromethyl)dioxirane [24]. 3-Arylidene-1-thioflavanones gave sulfones with mchloroperbenzoic acid as another electrophilic oxidant [17]. Thus, these electrophilic oxidants oxidize only the sulfur atom of the 3-arylidene-1-thioflavanones in a chemoselective reaction which may be a consequence of the strongly electron deficient character of the carbon-carbon double bond. For this reason, the nucleophilic oxidants alkaline hydrogen peroxide and sodium hypochlorite proved to be the reagents of choice for the epoxidation of 3-arylidene-1-thioflavanones [17,25,26]. Although the use of these oxidants afforded a diastereomeric mixture of the trans,cis-and trans,trans-epoxides, the two diastereomeric epoxides could easily be separated by silica gel column chromatography. Therefore, these stereohomogeneous epoxides are now available for further chemical transformations.Formerly, we have investigated the utility of the dimethyldioxirane (DMD), as a versatile electrophilic oxidant, for the oxidation of the sulfur atom of sulfur-containing six-and seven-membered heterocyclic compounds, viz. 4H-1-benzothiopyran-4-ones [27] and 2,3-dihydro-1,5-benzothiazepin-4(5H)-ones [28]. Depending on the amount of the oxidant, sulfoxides or sulfones were obtained. Moreover, in the case of the sulfoxidation of the 2-substituted 1,5-benzothiazepine derivatives a high trans diastereoselectivity was observed. All these results prompted us to study ...

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confidence: 99%

Dimethyldioxirane oxidation of the epoxides of (Z)‐3‐arylidene‐1‐thioflavanones

Lévai

Patonay

Tóth

et al. 2002

Journal of Heterocyclic Chem

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“…the configuration of the exo-double bond is retained during the oxidation. 11,12 The elucidation of the stereochemistry and relative configuration of the spiroepoxides was difficult owing to the equilibrium among boat-A envelope-A envelope-B boat-B conformers (Scheme 2), as can be seen by inspecting the Dreiding stereomodel. 5 Inversion of the hetero ring is connected with the interconversion of the quasi-axial (A) and quasi-equatorial (B) arrangements of the 2-phenyl group and the oxygen atom of the epoxide.…”

Section: Resultsmentioning

confidence: 99%

NMR and quantum‐chemical study of the stereochemistry of spiroepoxides obtained by oxidation of (Z)‐3‐arylidene‐1‐thioflavan‐4‐ones

Tóth

Kovács

Lévai

et al. 2001

Magnetic Reson in Chemistry

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Epoxidation of (Z)-3-arylidene-1-thioflavan-4-ones (1) yielded trans,cis (2) and trans,trans (3) isomers. The structure and signal assignments were elucidated by extensive application of one-and two-dimensional 1 H and 13 C NMR spectroscopy. The conformational analysis was achieved by the application of 3 J(C,H) couplings and ab initio MO calculations. Both the preferred ground-state conformers (envelope-A conformations) obtained as global minima of the HF ab initio structures and the 13 C chemical shifts calculated by the GIAO method from the global minima structures of the trans,cis and trans,trans isomers are in agreement with the experimentally obtained NMR results.

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“…Infrared spectra were recorded with a Shimadzu 470 infrared spectrophotometer (KBr wafer technique). 1 H NMR, 13 C NMR, and 15 N NMR spectra were recorded on a Bruker AMX 500 NMR spectrometer (400, 100, and 50.68 MHz, respectively) in DMSO-d 6 (for compounds 2b,c -CDCl 3 ) using TMS as the internal standard for 1 H and 13 C. Chemical shifts for 15 N are reported with respect to the external standard of saturated 15 NH 4 Cl in D 2 O. Chemical shifts are reported in ppm ( scale).…”

Section: Methodsmentioning

confidence: 99%

“…The structure of compounds 2a-c was elucidated using elemental analysis, mass spectrometry, IR and, particularly, NMR spectroscopy. The characteristic structural feature in the 1 H NMR analysis of 2c-h is the oxirane proton found at  values 4.5-5.2 ppm according to the type of the adjacent aromatic substituent [15,16]. Likewise, 1 H NMR spectra of compounds 2c-h indicated the presence of two isomers in equal amounts as shown by the existence of two oxirane proton signals.…”

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confidence: 99%