Blanka Wladislaw

Conformational studies of α-substituted carbonyl compounds. Part 1. Conformation and electronic interaction in hetero-substituted acetones by infrared and ultraviolet spectroscopy

νCO Frequencies and intensities and n→π* transition energies were measured for some heterosubstituted ketones (XCH2COMe : X = F, Cl, Br, I, NMe2, OMe, SMe, or SEt) and compared with the corresponding unsubstituted ketone. The stability of the gauche-conformers is discussed in terms of hyperconjugative interactions between σC – X and πCO orbitals and repulsive interactions between CO and C – X dipoles. The carbonyl frequency shifts, induced by inductive (ΔνI), field (ΔνF), and hyperconjugative effects (ΔνH), are estimated separately. A close relationship is shown to exist between the ΔνH values and the energies of the n→π* transition.

Asymmetric sulfoxidation of a β-carbonyl sulfide series by chloroperoxidase

Abstract The chloroperoxidase (CPO)-catalyzed oxidation of a series of β-carbonyl sulfides to sulfoxides has been studied at room temperature in aqueous citrate buffer. For dialkyl β-carbonyl sulfides, the products with methyl and ethyl substituents are obtained in ca. 100% yield. However when the alkyl group is n- propyl or i -propyl the yield drops dramatically (25%). An aryl sulfide derivative afforded product in very low yield (4%), but when the phenyl group bears a carbonyl, and the sulfur substituents are methyl or ethyl, the oxidation occurs with high yields (91–95%). Steric control of the sulfoxidation reaction is also confirmed with cyclohexanone derivatives, where a low product yield is observed even at high enzyme concentrations. Noteworthy are the yields obtained with cyclopentanone sulfide (65%) and an unexpected quantitative yield obtained with the γ-butyrolactone sulfide.

Sulfenylation of β-keto sulfoxides. III. Diastereoselectivity induced by a chiral phase transfer catalyst

Abstract The asymmetric induction in the sulfenylation of several β-keto sulfoxides under phase transfer catalytic conditions in the presence of the chiral catalyst N-benzylquininium chloride was investigated. It is concluded that the diastereoselectivity is not accompanied by enantiomeric resolution.

Interaction between the carbonyl group and a sulphur atom. Part 9. The relationship between conformation and ground- and excited-state interactions in some α-sulphur-substituted cycloalkanones

The conformations of some α-sulphur-substituted cycloalkanones are estimated approximately from the i.r. spectra. The decrease of the carbonyl stretching frequency in these compounds, by comparison with the corresponding unsubstituted ketones (ΔνCO), is reported and interpreted as due to hyperconjugative σC(2)–S–πCO interaction on the basis of the dependence on the position of C(2)–S bond. Similarly, hyperconjugative interaction in the excited state is proposed to account for the bathochromic shift of the n→π* band, at 300 nm, of the same compounds. The shorter wavelength u.v. absorption band, at 250 nm, is assigned to charge transfer from sulphur to the carbonyl group owing to its dependence on the position of the 3p orbital of sulphur relative to the carbonyl group.

α-Phosphoryl sulfoxides. XI. Sulfenylation of α-phosphoryl sulfoxides and a general synthesis of optically active ketene dithioacetal mono-S-oxides

Abstract Sulfenylation and selenenylation of α-phosphoryl sulfoxides 1 with S-methyl methanethiosulfonate and phenylselenenyl bromide, respectively, affording α-methylsulfenyl- and α-phenylselenenyl-α-phosphoryl sulfoxides 8 and 9 are described. Sulfenylation of (+)-(S)-dimethoxyphosphorylmethyl p-tolyl sulfoxide 2 gave a mixture of optically active diastereoisomers of the sulfoxide 8a which is a key substrate in the Horner-Wittig synthesis of enantiomeric ketene dithioacetal mono-S-oxides 10. The E Z ratio of geometrical isomers of 10 was determined and briefly discussed. The crystal and molecular structure of E-1-p-tolylsulfinyl-1-methylsulfenyl-2-phenyl-ethene 10a is reported.

Novel reaction: Decarboxylative Ramberg-Bäcklund rearrangement in some α-isopropyl sulfonyl carboxylic esters

The reaction of some isopropylsulfonyl α-mono and disubstituted esters with KOH/t-BuOH/CCl4 is reported For the α,α-dialkyl and α-monoaryl substituted derivatives the key step of this reaction is proposed to be the decarboxylative 1,3-displacement in the chlorinated intermediates.

SYNTHESIS AND CHARACTERIZATION OF COMPLEXES OF RARE EARTH PICRATES AND RAC-BIS(ETHYLSULFINYL)METHANE

Abstract The compound β-dissulfoxide bis(ethylsufinyl)methane (besm) was prepared by oxidation of bis(ethylthio)methane with hydrogen peroxide in acetic acid, and obtained as a mixture of its meso and d,1 diastereomers. An analytical sample was obtained by recrystallization from chloroform-diethyl ether. The racemic-bis(ethylsulfinyl)methane was characterized and studied by CHS elemental analysis, high resolution mass spectrometry, infrared spectra, 1H and 13C NMR. A series of compounds with composition RE(pic)32rac-besm [RE = La, Ce, Nd, Eu, Gd, Er, Tm, Yb, Lu and Y; pic = picrate and rac-besm = racemic-bis(ethylsulfinyl)methane] were synthesized and characterized by CHNS elemental analysis and rare earths complexometric titration with EDTA, conductance measurements, X-ray powder patterns, infrared spectra, visible absorption of the neodymium and emission spectra of the europium materials. The coordination polyhedron around the Eu3+ center is probably a dodecahedron with coordination number eight.

Conformational studies of α-substituted carbonyl compounds. IV: Electronic interaction in 2-thiasubstituted carbonyl systems. ω-Ethylthio-p-substituted acetophenones

Abstract The carbonyl stretching frequencies and the apparent molar absorptivities are reported for some ω-ethylthio-p-substituted acetophenones and for the corresponding unsubstituted acetophenones. In the ω-ethylthio-series the solvent effect indicates the presence of the cis/gauche rotational isomerism, being the gauche rotamer predominant in the whole series (ca. 90%). In the ω-ethylthioacetophenones, on going from electron-attracting to electron-donating substituents, the progressive increase in the carbonyl cis shifts (Δνc) is attributed to the increasing Field Effect between C[dbnd]O and C[sbnd]S dipoles, and the progressive decrease in the carbonyl gauche shifts (Δνg) is due to the deacreasing contribution of the hyperconjugative interaction between πCO and σc[sbnd]s orbitals. The U.V. spectra of the ω-ethylthioacetophenones display a n → π∗CO band which is bathochromically shifted in relation to the corresponding acetophenones, indicating the occurrence of the hyperconjugative interaction between...

SULFANYLATION REACTIONS OF CARBONYL COMPOUNDS AND CARBOXYLIC ACID DERIVATIVES EMPLOYING SULFUR ELECTROPfflLES. A REVIEW

1 . in situ Oxidation of Thiols or Thiolates ................................................................................. 450 2 . Electrochemical Generation of the Sulfanylating Agent ....................................................... 451 I1 . CATALYTIC METHODS ...................................................................................................... 451 III . monoversus bis-SULFANYLATION .................................................................................. 453 IV . REGIOAND CHEMOSELECTIVITY ............................................................................. 456 V . STEREOSELECTIVE SULFANYLATION REACTIONS .............................................. 458

New decarboxylation, de-ethoxycarbonylation and desulfonylation, followed by sulfenylation of some half-esters of malonic acids and α-sulfonylmalonic esters

The sulfenylation of some half-esters of malonic acids and some α-sulfonylmalonic esters with several sulfenylating reagents was investigated. Evidence was provided that in the case of the half-esters, in which NaH–dimethyl sulfoxide was employed, the formation of α,α-disulfenylated carboxylic esters may occur by two different reaction sequences, initiated either by dianion formation or decarboxylation. It is shown that, in the case of the α-sulfonylmalonic esters, in which diazabicyclooctane in refluxing toluene was employed, two competitive reactions may take place: de-ethoxycarbonylation or desulfonylation, both followed by sulfenylation.