Search

Chemical shifts of the ethylenic protons Hα and Hβ in cis and trans β-arylthio-,β-arylsulfinyl- and β-arylsulfonyl-acrylic acids have been determined in acetone and in Na2CO3/D2O solution. The absorption signals were assigned unambiguously by β-deuteration. An increase of electron-withdrawing power of the β-substituent (ArSO2 > ArSO > ArS) causes an increase in shielding of Hβ proton and a decrease in that of Hα proton. The τ-values of the Hβ protons are lower in the trans than in the corresponding cis acids, which may be explained in terms of magnetic anisotropy effects of the carboxyl group in the trans acids. Generally, the τ-values of the Hβ protons are lower, and those of the Hα protons higher, in acetone than in Na2CO3/D2O solution; this is probably due to differences in electron-withdrawing power of the COOH and COO⊙ groups. In all trans derivatives the average values of the coupling constants Jαβ are 15.3 c./sec., and lie between 10.1-11.4 c./sec. for the cis derivatives. The effects of para-substituents (CH3O, CH3, H, Cl, NO2) on the chemical shifts of the Hα and Hβ protons in cis and trans β-arylthio-, β-arylsulfinyl-, and β-arylsulfonyl-acrylic acids are correlated with the Hammett σ-constants.

The stereochemical course of the 1,4-cycloaddition of thioaldehyde S-oxides (monosubstituted sulfines) to 2,3-dimethylbuta-1,3-diene, buta-1,3-diene, and cis- and trans-penta-1,3-diene was investigated. Unexpectedly, the reactions of buta-1,3-diene and 2,3-dimethylbuta-1,3-diene with Z-monoaryl sulfines afforded cis/trans mixtures of the corresponding dihydrothiopyran S-oxides, in which the relative amounts of the two isomers depended upon the initial diene/sulfine ratio. A Z to E isomerization of the dienophiles during the cycloaddition was responsible. On the other hand, Z/E mixtures of aliphatic tert-butyl sulfine gave, with 2,3-dimethylbuta-1,3-diene, only the corresponding trans cycloadduct. Catalysis of the reaction by Lewis acids, heretofore largely unexplored, was also investigated

Aromatic and aliphatic, not enethiolizable, thioaldehyde S-oxides (monosubstituted sulfines) are obtained from stereospecific fluorodesilylation of the corresponding thioacylsilane S-oxides with retention of configuration. A detailed investigation on the mechanism of the desilylation, as well as of the acid and fluoride ion induced Z/E interconversion has been performed

Thiolatecobalt carbonyls RSCo(CO)4, 1 (R = Me, a, Et, b, PhCH2, c, Ph, d) and RSCo(CO)3PPh3, 2 (R = Et, a, PhCH2, b) were prepared. Complexes 1 were obtained from Co2(CO)8 or ICo(CO)4 and RS− or from Co2(CO)8 and RSSR, complexes 2 were prepared by substitution of 1 by PPh3 or by the reaction of ICo(CO)3PPh3 with RS−. Complexes 1 yield desulfuration products and/or polynuclear sulfur containing cobalt carbonyl clusters. Einkernige Thiolatcobaltcarbonyl-Komplexe Thiolatcobaltcarbonyle RSCo(CO)41 (R = Me, a; Et, b; PhCH2, c; Ph, d) und RSCo(CO)3PPh32 (R = Et, a; PhCH2, b) wurden dargestellt. Die Komplexe 1 wurden von Co2(CO)8 bzw. ICo(CO)4 und RS− oder von Co2(CO)8 und RSSR erhalten; die Komplexe 2 wurden durch Substitution von 1 mit PPh3 oder durch Umsetzung von ICo(CO)3PPh3 mit RS− dargestellt. Die Komplexe 1 ergeben desulfurierte Produkte und/oder mehrkernige schwefelhaltige Cobaltcarbonyl-Cluster.

Thiolatecobalt carbonyls RSCo(CO)4, 1 (R = Me, a, Et, b, PhCH2, c, Ph, d) and RSCo(CO)3PPh3, 2 (R = Et, a, PhCH2, b) were prepared. Complexes 1 were obtained from Co2(CO)8 or ICo(CO)4 and RS− or from Co2(CO)8 and RSSR, complexes 2 were prepared by substitution of 1 by PPh3 or by the reaction of ICo(CO)3PPh3 with RS−. Complexes 1 yield desulfuration products and/or polynuclear sulfur containing cobalt carbonyl clusters. Einkernige Thiolatcobaltcarbonyl-Komplexe Thiolatcobaltcarbonyle RSCo(CO)41 (R = Me, a; Et, b; PhCH2, c; Ph, d) und RSCo(CO)3PPh32 (R = Et, a; PhCH2, b) wurden dargestellt. Die Komplexe 1 wurden von Co2(CO)8 bzw. ICo(CO)4 und RS− oder von Co2(CO)8 und RSSR erhalten; die Komplexe 2 wurden durch Substitution von 1 mit PPh3 oder durch Umsetzung von ICo(CO)3PPh3 mit RS− dargestellt. Die Komplexe 1 ergeben desulfurierte Produkte und/oder mehrkernige schwefelhaltige Cobaltcarbonyl-Cluster.

t-Butyl and methyl trimethylsilyl thioketones have been synthesized, and the reactivity towards organometallic compounds, dienes, and oxidation, and the desilylation of the resulting adducts, have been investigated. Where possible, a comparison with aryl trimethylsilyl thioketones has been made.

Aryl silyl thioketones react with 1,3-dipoles (nitriloxides, nitrilimine and nitrile ylide) to give regiospecifically silyl thiaheterocycles. These cycloadducts undergo desilylation leading either to ring fragmentation products or to the H-substituted heterocycles

t-Butyl and methyl trimethylsilyl thioketones have been synthesized, and the reactivity towards organometallic compounds, dienes, and oxidation, and the desilylation of the resulting adducts, have been investigated. Where possible, a comparison with aryl trimethylsilyl thioketones has been made.

Microwave spectra of the ground and first three excited torsional states of N -sulphinylaniline have been assigned. The variation of the inertial defect with torsional number shows the molecule to be planar. The torsional frequency has been determined as ν = 41.1 cm −1 and the barrier to internal rotation as V 2 = 2.3 kcal/mole. From the splittings of the Stark lobes of some lines the values μ a = 2.20 ± 0.06, μ b = 0.664 ± 0.005, and μ tot = 2.30 ± 0.06 were obtained.

Conjugated nitrosoalkenes, generated in situ via dehydrobromination of α-bromoketoximes, undergo an easy [4+2]-cycloaddition with thiocarbonyl compounds to give very high yields of the new heterocycles 4H-1,5,2-oxathiazines. The thermolysis and the behaviour to oxidation of these adducts were tested.

Trimethylsilyl and triphenylsilylaryl thioketones have been synthesized by acid catalysed reaction of the corresponding ketones with hydrogen sulphide. Such silylated thioketones have been oxidized to give S-oxides and converted with diaryldiazomethanes into triaryl thiiranes; upon treatment with organolithium nucleophiles they undergo thiophilic addition. The ready desulphurization with triphenylphosphine of silylated thiirans to the corresponding silyl triaryl ethylenes is also reported.

Silylated thiirans upon oxidation with peroxyacids do not give exclusively the corresponding S-oxides but, in addition some products derived from ring opening. The stereochemistry of the oxidation to thiiran-1-oxides is anti to the silyl group as demonstrated by X-ray analysis.

The reaction of R-(-)-methyl-α-naphtyl-phenylsilyl phenyl thioketone 1 with organolithium derivatives and Grignard reagents gives the α-silylsulphides 3 with medium to good levels of asymmetric induction. The asymmetry induced at the α-carbon is retained in the subsequent desilylation.

Aus den beiden Sulfinen (I) und den Diazoverbindungen (II) entstehen um 10°C die Episulfoxide (III), wobei mit unsymmetrischen Ausgangsverbindungen auch die isomeren Sulfoxide (IV) erhalten werden.

The E.S.R. spectra of a number of diazine and naphthyridine anions are interpreted using molecular orbital theory. Results obtained with different theoretical procedures are compared and discussed.

The rates of the base-catalysed H–D exchange in endo- and exo-2-methoxycarbonylnorbornene and in endo- and exo-2-phenylsulphonylnorbornene have been measured. In the first two compounds the exchanges occur α to the methoxycarbonyl group; in the second two compounds α to the phenylsulphonyl group. The rates are slightly lower in the esters than in the sulphones, in accordance with the pKa values of simple carboxylic esters and alkyl sulphones. In the disubstituted norbornenes, methyl cis-endo- and cis-exo-3-phenylsulphonyl-bicyclo[2,2,1]hept-5-ene-2-carboxylates, there is isotopic exchange only at the position α to the methoxycarbonyl group, and inversion of the latter, endo→exo and exo→endo respectively; the exchange and inversion rates are identical. The trans-isomers remain unchanged in the reaction conditions of the cis-isomers. The results have been compared with those obtained in the case of the corresponding disubstituted norbornene acids. They are consistent with a pyramidal structure (sp3-hybridisation), and not with a planar structure (sp2-p-hybridisation) of α-sulphonyl carbanions in the norbornene system.

The title compound was prepared by acid catalysed reaction of the corresponding ketone with hydrogen sulphide, and its ability to transfer chirality to the carbon α to silicon in reactions with buta-1,3-diene and methyl-lithium was tested; good levels of asymmetric induction were observed.

(E)-Phenyl and (E)-(p-tolyl) trimethylsilyl thioketone S-oxides can be easily and stereospecifically protodesilylated into the corresponding (Z)-aryl thioaldehyde S-oxides; these stable liquid lachrimatory compounds show good reactivity as heterodienophiles and the reaction with 1,3-dienes is surprisingly non-stereospecific.

Diarylthioketone S-oxides react with the 2H-azirine (1) in the presence of boron trifluoride–diethyl ether to give the oxathiazines (3)via a 1,3-cyclization across the sulphine C–S–O bond; the oxathiazines (3) rearrange thermally to the sulphoxides (5).

Die Reaktion von Dichlorsulfin (I) mit dem Diazoderivat (II) fuhrt uber die angegebenen, nicht isolierbaren Zwischenprodukte (III)-(V) zu der Titelverbindung (VIa).