Stereochemistry of organic sulphur compounds. part 13. Configurational assignment of diastereoisomers of 2-methylsulphinyl-1,2-diphenylethanol and of their O-methyl and O-acetyl derivatives

The synthesis, isolation and conformational analysis of the diastereomeric 2-methylsulphinyl-1,2-diphenylethanol and of its $\text{O}$-methyl and $\text{O}$-acetyl derivatives are reported. Chemical correlations and the study of the influence of solvent polarity changes on the coupling constants have permitted the configurational assignment. Lanthanide shift reagents have been used also. to this effect. The role of hydrogen bonding in the hydroxysulphoxides has been evaluated in diluted solutions by IR and NMR spectroscopy. A donor-acceptor interaction between oxygen and sulphur has been invoked to explain the differences in conformational behaviour between epimeric sulphoxides at sulphur atom.     

Stereochemistry of organic sulphur compounds : Part. 17 conformational analysis of some erythro- and threo-thio-derivatives of β-fluorinated and β-oxygenated ethanes

The synthesis and conformational analysis of 2-fluoro, 2-hydroxy and 2-methoxy thioderivatives (thioethers, sulphoxides, sulphones and sulphonium salts) of 1,2-dimethyl and 1,2-diphenylethanes ($\text{erythro}$ and $\text{threo}$) are reported. Steric effects in thioethers and electrostatic interactions in sulphonium salts are the main factors determining the stability rotamers. A balance of these factors controls the conformational equilibria in sulphoxides and sulphones. Electronic interactions between the $\text{π}$-aromatic electrons or the unshared β-heteroatomic electrons and the sulphur atom are suggested to explain large differences in rotamer populations induced by changes in the carbon sketelon or in the relative configuration of the sulphinylic sulphur.     

Stereochemistry of organic sulphur compounds. part 14 . synthesis and conformation analysis of 1-thioderivatives of 3,3-dimethyl-2-butanol and its acetates

The synthesis and conformational analysis of some thioderivatives But-CHX-CH₂Y (X = OH and OAc: Y = SH, SMe, SO₂Me and SMe₂) are reported. The conformational equilibra have been established from IH-NMR data and high dilution ir studies. All the compounds exhibited almost monoconformational behaviour around the C(1)-C(2) bond, due to strong steric factors. The observed vicinal coupling constants were used to check the different parameterizations of Altona's equation for our compounds with sulphur in distinct oxidation states. The possible dihedral angle deformations were also evaluated.     

Mineralization of some organic sulphur compounds by fusion with molten alkali

The action of molten alkali-metal hydroxides for the destruction of organic matter containing sulphur has been studied. Various procedures were developed which differed mainly in the initial phase of the process, mainly with respect to homogenization of the reaction mixture, but also with regard to addition of an auxiliary oxidant. The technique is not universally applicable to sulphur compounds, but is useful for decomposition of sulphur compounds with m.p. > 150 degrees and containing sulphonate, thiocarbonyl, phenazothionium and thio groups. The sulphur is converted into sulphate, which is then determined as barium sulphate.     

Stereochemistry of the primary carbon—X Stereochemical configurations of some optically active deuterium compounds

The isobornyloxymagnesium halide reduction of the appropriate deutero-aldehyde yields benzyl--d alcohol and 1-butanol-1-d having the same configuration and about the same level of optical purity. Arguments are presented that these alcohols are close to optical purity. The relative configurations of each alcohol were established by converting each to 1-phenylbutane-1-d using reactions of known or presumed stereochemistry. The rotations and configurations of 18 optically active deuterium compounds are summarized.     

Carbon-13 chemical shift assignment of some organophosphorus compounds: 1—Dialkyl and diaryl (alkylamido)phosphates with general formula Y2P(X)NHR

Carbon-13 chemical shifts and the POC, POCC, PNC and PNCC coupling constants of 18 compounds containing the amine moiety, and with the general formula Y₂P(X)NHR [Y=C₂H₅O, C₆H₅O, CH₂O, Y₂=1,2-dioxybenzene; X = O or S; R = H, CH₃, C₂H₅, PhCH₂CH₂, (CH₃)₂CH, C(CH₃)₃, C₆H₁₁, C₆H₅, C₆H₅NH] have been determined. The Y₂P(X) group shows a sterically induced effect on the amine moiety; the ¹³C chemical shift of the Y group is, however, almost unaffected on replacing P(O) by a P(S) group.     

Stereochemistry of alkyl 3-substituted 4-halotetrahydro-2-oxo-3-furancarboxylates: 2—1H and 13C NMR spectra

The ¹H NMR parameters of methyl 3-substituted cis-4-halotetrahydro-2-oxo-3-furancarboxylates are reported, with assignments of the ring protons based on solvent-induced changes in the vicinal trans coupling constants, ³J(H-4, H-5). Preferred conformations, ce with a pseudo-equatorial halogen for the cis isomers and ta with a pseudo-axial halogen for the trans isomers, have been suggested on comparison of the magnitudes of J(trans) and J(gem) in both series. The ³J(¹³CH₃, H-4) values measured for methyl cis-4-bromotetrahydro-3-methyl-3-furancarboxylate, methyl trans-4-bromotetrahydro-3-methyl-3-furancarboxylate and trans-3,4-dibromodihydro-3-methyl-2(3H)-furanone have confirmed the stereochemical assignments.     

Fluorovinyl organometallic compounds — an historical review and some recent advances

This review describes the historically important routes to fluorovinyl organometallic species of the type M-(CX=CX₂), where M is a main-group or transition-metal element and one, or more, of the substituent atoms, X, is fluorine, the others being either other halogens, or hydrogen. A number of newer synthetic methods are described which have resulted in the preparation of a wider range of examples of such compounds. The structure, spectrocopy, properties, reactivity and future prospects for this class of compounds are described.     

The negative ion mass spectra of mixtures of sulphur and organic compounds. I—The formation of [M+Sn]− from the mixture of sulphur and dinitriles

The negative ion mass spectra of sulphur, dinitriles and their mixtures were studied. The abundance of negative ions of sulphur was almost comparable to that of positive ions. In the negative ion mass spectrum of a mixture of sulphur and dinitrile, intense and characteristic peaks of [M + S_n]^? (n = 2, 3, 4, etc.) were observed resulting from ion–molecule association of dinitrile with the S_n^? anions. As a standard sample of a negative ion mass spectrum, sulphur itself has proved useful in the lower mass region (below m/e 256: S₈^?).     

Mass spectrometry of organic compounds of group V elements 7—N-alkoxyamines

The suggestion of participation of the participation Ione electron pair of the nitrogen atom in amine-type stabilization has been confirmed by a decrease in amine-type fragmentation and a drastic change in the decomposition routes under electron impact of N-alkoxyamines.     

Mass spectrometry and organic analysis—XII αβ-Unsaturated secondary alcohols

The fact that some αβ-unsaturated alcohols give mass spectra that bear some similarity with the corresponding saturated ketones is discussed, and the double hydrogen transfer necessary to accommodate this is examined by deuterium labelling.     

Configurational assignment by 13C NMR of stereoisomeric 3-bromo-3-acyl derivatives of 5α- and 5β- androstane

The configurational assignment of stereoisomeric 3-bromo-3-acyl derivatives of steroids in both the 5α and 5β series has been carried out by comparing the ¹³C chemical shifts of C-3. A downfield shift is observed for C-3, bearing a bromine and an acyl group, on going from the isomer with an equatorial bromine to that with an axial bromine. This rule has been established by comparison of the ¹³C chemical shifts of model compounds in 4-tert-butylcyclohexanes of known configuration.     

The negative ion mass spectra of mixtures of sulphur and organic compounds. II—the formation of [C5H5 + Sn]− from the mixture of sulphur and ferrocene

The negative ion mass spectra of ferrocene and of a mixture of ferrocene with sulphur were studied. In the spectrum of the mixture, characteristic peaks of [C₅H₅ + S_n]^? (n = 1, 2, 3 etc.) were observed. The structures of these ions are discussed.     

Fragmentation of organic compounds on electron-impact—V: 1,1-Dichlorocyclopropanes

The mass spectral fragmentation reactions of twenty-one 1,1-dichlorocyclopropanes prepared from various isomeric octenes are discussed. The most characteristic reaction may be represented as follows: The importance of this fragmentation and the distribution of the positive charge between the species produced is a function of the degree of branching in the molecule. The more highly branched isomers produce less characteristic fragmentation patterns. The identification of isomeric octenes from the fragmentation patterns of the corresponding 1,1-dichlorocyclopropanes is discussed.     

Configurational assignment of fragment ions by CID. Stereochemistry and mechanism of retro-Diels–Alder fragmentation accompanied by hydrogen transfer in gas-phase cations

Low energy CID mass spectra of m/z 173, C₈H₁₃O₄⁺, obtained from the diethyl ester of cis,syn,cis-l,2,3,3a,4,5,5a,6,7,8-decahydroindacene-4,5-dicarboxylic acid and cis,syn,cis-l,2,3,4,5,6,7,8,8a,9,10,10a-dodecahydrophenanthrene-9,10-dicarboxylic acid indicate they have the structure of protonated diethyl maleate. This finding together with previous deuterium labelling results suggest that the formation of this ion from both precursors takes place by migration of a hydrogen atom from an allylic δ-position followed by the concerted cleavage of two allylic C? C bonds in analogy to the ground state retro-Diels–Alder fragmentation.     

Studies in sulphur heterocyles. 2—The 13C NMR spectra of thienocoumarins

¹³C NMR spectra of 3- substituted thieno[2,3-h][1]benzopyran-2-ones and 8-substituted thieno[3,2-f]-[1]benzopyran-7-ones are reported and the substituent dependence of certain ¹³C chemical shifts is noted.     

Stereochemistry of amino-carbonyl compounds—VII: Absolute and ralative configuration of some diastereomeric 1,3-amino-alcohols.

The absolute configuration of (+)-4-dimethylamino-2,4-diphenyl-butan-2-ol and (+)-4-piperidino-2-phenyl-pentan-2-ol, the predominant diastereomers obtained by reaction of (+)-3-dimethylamino-1,3-diphenyl-propan-1-one with MeLi and (+)-3-piperidino-1-phenyl-butan-1-one with MeMgI, respectively, was determined by chemical correlation. The relative configurations of the diastereomers afforded by such reactions were thus assigned.     

α‐Pinene and myrtenol: complete 1H NMR assignment

The complete analysis of the ¹H NMR spectra of α‐pinene and myrtenol is reported and earlier results are corrected. Copyright © 2002 John Wiley & Sons, Ltd.