3-Aryl-4,5-dichloro-1,2,3-thiadiazolium salts — Synthons for the preparation of mesoionic compounds of the 1,2,3-thiadiazole series

The high mobility of the chlorine atom at the 5-position of 3-aryl-4,5-dichloro-1,2,3-thiadiazolium salts facilitates a ready preparation of mesoionic 3-aryl-1,2,3-thiadiazoles with an exocyclic oxygen, sulfur or arylimino group at the 5-position. In an aqueous alcoholic solution of sodium nitrite, the halogens in the 4- and 5-positions are substituted with the formation of 3-aryl-5-nitro-1,2,3-thiadiazolium-4-olates.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1552–1554, November, 1989.     

Ätherspaltungen mit magnesium : III. Kriterien für die spaltbarkeit von thioäthern

Only 7 out of 25 thioethers investigated were attacked by magnesium in boiling tetrahydrofuran. It seems that the presence of a thiophenyI group in combination with an sp² carbon atom in the β-position on the other side of the sulfur atom is necessary for cleavability. Allyl methyl sulfide, in contrast to allyl methyl ether, is not cleaved. The cleavable thioethers, on the other hand, react faster than the corresponding oxygen ethers.In order to explain the selective cleavability of the thioethers under investigation it is assumed that the sulfur atom while partially positive by resonance with the phenyl ring attracts electrons interacting with the α,β- or β,γ-π electron systems, respectively. The rate-determining step of the reaction is the electron transfer from the magnesium to the thioether followed by detachment of the unsaturated group from the sulfur, presumably as a radical. The stability of the finally by another electron transfer formed organomagnesium compound therefore has no influence on the cleavability of the thioethers.     

Reaction of salts of nitroaminotetrazoles with alkyl iodides

The reaction of salts of 5-nitroaminotetrazole, 1- and 2-methyl-5-nitroaminotetrazole, and 2-ethyl-5-nitroaminotetrazole with alkyl iodides is studied. It is established that salts of 2-methyl- and 2-ethyl-5-nitroaminotetrazole are alkylated at the nitroamine group while salts of 1-methyl-5-nitroaminotetrazole are alkylated at the second nitrogen atom of the tetrazole fragment with the subsequent splitting off of the methyl group at the 1-position of the tetrazole ring and further alkylation of the nitroamine group. It is shown that salts of 5-nitroaminotetrazole are initally alkylated at the second nitrogen atom of the tetrazole fragment and then at the nitroamine group. It is hypothesized that the initial alkylation of salts of 1-methyl-5-nitroaminotetrazole and 5-nitroaminotetrazole at the second nitrogen atom of the tetrazole fragment results from their nitroimino tautomeric form.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1090–1093, August, 1986.     

Pyramidal Inversion in Cyclic Sulfonium Salts

5- and 6-membered cyclic sulfonium salts carrying methyl substituents on the ring have been synthetized and partially resolved. These salts undergo thermal stereomutation at rates which are 10³ times lower than that of non-cyclic sulfonium cations. Very stringent evidence is presented that racemisation or, where the case may be, epimerisation takes place by pyramidal inversion of the sulfur atom.     

Oxidative imination of sulfur-containing heterocycles

For the first time, the sulfur heteroatom of 4-oxothiazolidines has been iminated with sodium salts of chloroamides of arenesulfonic acids and N-chloroamides of carboxylic acids. The effect of the substituents and the size of the ring on the ability of the ring sulfur atom to undergo oxidative imination was studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 609–612, May, 1979.     

Cyclization of 2- and 3-indolythioalkanoic acids to novel indole-containing tricyclic ring systems

A series of 2- and 3-indolylthioalkanoic acids of various chain lengths were cyclized under dehydrative conditions affording tricyclic indole-containing ring systems wherein the third ring contains a sulfur atom attached to the 2- or 3-position of the indole ring. This methodology affords entry into the novel thiepino[3,2-b]indole, thiocino[2,3-b]indole and thiocino[3,2-b]indole ring systems.     

New Perspectives in Thiazole Chemistry

Abstract

Carbon-carbon bond forming reactions at C-2 of the thiazole ring have been carried using two strategies, one involving the addition of organometallic reagents (lithium carbanions of esters, Grignard salts, silyl enol ethers, silyl ketene acetals, silylazoles) to N-acylthiazolium salts; the other involving the addition of carbon electrophiles (ketenes, acyl chlorides, anhydrides, aldehydes) to N-acylthiazolium ylides generated in situ. The reactions have been applied to 1,3-thiazole and 2-trimethylsilyl-1,3-thiazole, the latter being more reactive than the former toward electrophiles. This methodology constitutes a new entry to a variety of functionalized thiazoles and thiazolines which are potential building blocks for the synthesis of natural compounds and analogues of biologically active molecules (penems, arylpropionic acids). Some ring transformations of thiazoles induced by carbon-sulfur bond cleavage are also described. The fundamental role played by the sulfur atom of the thiazole ring in the observed reactions is pointed out and briefly discussed.     

Quantum Chemical Study of Mechanisms of Organic Reactions: VII. Reaction of Ethane-1,2-dithiol with 1,3-Dichloropropene in the System Hydrazine Hydrate–KOH

A mechanism has been proposed for the reaction of 1,3-dichloropropene with ethane-1,2-dithiol in the system hydrazine hydrate–potassium hydroxide on the basis of DFT quantum chemical calculations [B3LYP/6-311++G(d,p)]. The proposed mechanism involves several consecutive steps, in particular nucleophilic substitution of chlorine at the sp³-hybridized carbon atom by sulfur, prototropic allylic rearrangement of the monosubstitution product with double bond migration toward the sulfur atom, dithiolane ring closure via nucleophilic attack of the second thiolate group on the carbon atom in the γ-position with respect to the second chlorine atom, and prototropic allylic rearrangement of 2-vinyl-1,3-dithiolane to more stable 2-ethylidene-1,3-dithiolane.     

Sodium thiosulfonate salts: molecular and supramolecular structural features and solution radiolytic properties

Three sodium thiosulfonate salts, NaMeS(2)O(2)·H(2)O, NaPhS(2)O(2) and NaMeC(6)H(4)S(2)O(2) have been prepared by the direct reaction of the sodium sulfinate salts with elemental sulfur, a clean, benign route that produces no by-products. The structures of the phenyl (which crystallised as a hydrate, NaPhS(2)O(2)·1.5H(2)O) and p-tolyl compounds were determined by X-ray crystallography. For the p-tolyl derivative, NaMeC(6)H(4)S(2)O(2), the unexpected coordination of the pendant sulfur atom was found, a feature not reported previously for thiosulfonate salts, and observed only in two of the more common thiosulfate salts. Intermolecular CH/π interactions are postulated to contribute to the driving force of sulfur coordination, otherwise a different orientation of the aromatic rings would be expected. For NaPhS(2)O(2)·1.5H(2)O, the water ligands and thiosulfonate anions each contribute three oxygen atoms to form a NaO(6) coordination sphere. The thiosulfonate and water oxygens bridge to other sodium atoms forming a three-dimensional layer structure consisting of sheets of NaPhS(2)O(2)·1.5H(2)O with a hydrophilic interior layer, comprising the sodium ions, water ligands and -S(2)O(2)(-) groups, and a hydrophobic exterior formed by the phenyl substituent. The structure is further stabilised by an extensive H-bonding network between the ligated water and the non-coordinating thiosulfonate sulfur atom forming part of the hydrophilic layer and by weak intermolecular edge-to-face CH/π interactions between the sheets. Investigation of the radical chemistry of the three salts using pulse radiolysis indicated that oxidation of NaMeS(2)O(2)·H(2)O involves formation of a sulfur-centred radical rather than hydrogen abstraction from the methyl substituent, whereas oxidation of the aromatic ring is the preferred pathway for the phenyl and p-tolyl derivatives.     

Adsorption characteristics of tripodal thiol-functionalized porphyrins on gold

X-ray photoelectron and Fourier transform infrared spectroscopy studies are reported for self-assembled monolayers (SAMs) of two tripodal thiol-functionalized metalloporphyrins (Zn and Cu) and three benchmark tripods on gold substrates. The tripodal unit common to all five molecules is 1-(phenyl)-1,1,1-tris(4-mercaptomethylphenyl)methane (Tpd). Both porphyrins contain S-acetyl-protected thiols and are linked to the 4-position of the phenyl ring of Tpd via a phenylethyne group. The benchmark molecules include (1) two tripods containing a bromine atom at the 4-position of the apical phenyl ring, one a free thiol and the other its S-acetyl-protected analogue, and (2) a S-acetyl-protected tripod containing a phenylethyne unit at the 4-position of the apical phenyl group. Together, the spectroscopic studies reveal that none of the five tripodal molecules bond to the gold surface via all three sulfur atoms. Instead, the average number of bound thiols ranges from 1.5 to 2, with the porphyrinic molecules generally falling at the middle to upper end of the range and the smallest benchmark tripods falling at the lower end. Similar surface binding is found for the S-acetyl-protected and free benchmark tripods, indicating that the presence of the protecting group does not influence binding. Furthermore, the surface binding characteristics of the SAMs are not sensitive to deposition conditions such as solvent type, deposition time, or temperature of the solution.     

Reaction of thieno[2,3-d]pyrimidines with mercury salts

The reaction of mercury salts with thieno[2,3-d]pyrimidine derivatives was studied. It was shown that even in nucleophilic solvents the solvatomercuration of thienopyrimidines is accompanied by intramolecular ring closure involving the sulfur atom of the thioureide group.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1141–1143, August, 1987.     

ELECTRONIC EFFECTS OF POLYFLUORINATED SUBSTITUENTS ON THE POLYMERIZATION AND THE PROPERTIES OF POLYTHIOPHENES

Three series of polythiophenes containing fluoroalkoxy and fluoroether substituentswere prepared by electrochemical polymerization. The effect of substituents with fluoro-alkoxy or ether functional groups on the electrochemical polymerization of thiophene mono-mers and properties of the obtained polymers were analyzed. The introduction of a flu-oroether functional group at the 3-position of the thiophene ring leads to an increase ofthe oxidation potential of the monomer and to a decrease of the conductivity of the re-sulting polymers, even with the use of a CH_2 group as spacer. Conversely, the presenceof an oxygen atom directly at the 3-position of the thiophene ring, which offsets the nega-tive withdrawing effect of fluoroalkyl groups, facilitates the synthesis of highly conductingpolythiophenes.     

Fragmentations de quelques Derives thiophosphores sous L'impact electronique. II—Migration de groupes phenyles et d'atomes de soufre dans quelques derives dithiophosphores

Some compounds having two diphenylphosphino or diphenylthiophosphoranyl groups give rise by electron-impact-induced fragmentation to varied migrations of phenyl groups or of sulfur atoms. According to the compound, the phenyl moves by migration from one phosphorous to the other, or to the sulfur which is bound to the other phosphorous. Migration of the phenyl from the phosphorous towards the carbon arises when this is strongly electrophilic. The thiophosphorous compounds also give rise to sulfur atom migrations from the phosphorous to the carbon, or to the double bond placed in α of phosphorous atom.     

A New Route to Mercury-Containing Triphenylphosphonium Salts with Electron-Withdrawing Groups at the P Atom and Some Transformations of These Compounds

(Aroylmethyl)triphenylphosphonium salts react with mercury(II) trifluoroacetate with replacement of the labile methylene hydrogen atom by the HgOCOCF₃ group to give mercury-containing triphenylphosphonium salts in quantitative yields. Treatment of the mercurated salts with potassium carbonate yields mercury-containing triphenylphosphonium ylides of symmetrical and unsymmetrical structures, which enter Wittig reaction with aromatic aldehydes to form the corresponding mercurated olefins (Z isomers) and triphenylphosphine oxide.     

Mode of oxidations of organosulfur compounds: Example of nucleophilic oxygenations of thiolsulfinates

Two types of oxygenative oxidations (Nucleophilic and Electrophilic Oxidations) of sulfur atom are proposed and a typical mode of nucleophilic oxidation is shown with a few unsymmetrical thiolsulfinates.     

On the cyclization of ortho-alkynylbenzene diazonium salts

Cyclization of ortho-(phenylethynyl)benzene diazonium salts containing groups of +C character at the para-position of the phenyl ring proceeds with closure to a pyrazole, but not to a pyridazine as is the case in the presence of neutral or −C groups.     

Molecular structure and estrogenic activity—I Unsymmetrical diphenylethylenes and triphenylethylenes

Variation in the planarity of estrogenic substituted ethylenes has been studied by means of U.V. absorption.

1. In the unsym-dianisylethylenes, β-substituents increase the steric hindrance. Symmetrical and unsymmetrical twisting of the rings is discussed.

2. Preceding results are extended to trianisylethylene in which different structures are considered: partially non-planar anethole, cis-, and trans-di-p-methoxystilbene. Introduction of a β-chloro atom causes the twisting of all aromatic groups out of the double bond plane. Thus π-π conjugation is considerably reduced giving rise to a new band which is practically not affected by the presence of para-methoxy substituents. Increase of estrogenic activity is correlated with this structural modification.

3. Non-planarity alone of a single ring is not sufficient to induce high estrogenic activity, the second ring in the -position is itself necessary for high activity and the unsym-diphenylethylene structure seems to play an important role in the activity of the halogenated-triphenylethylenes. This may explain several findings reported in the literature.

4. The relation between estrogenic activity and structure in these substituted ethylenic compounds should be discussed not only in terms of spatial structure but also as in terms of electron distribution.     

Ditocopheryl Sulfides and Disulfides: Synthesis and Antioxidant Profile

Symmetrical ditocopheryl disulfides ( Toc ) ₂ S₂ and symmetrical and unsymmetrical ditocopheryl sulfides ( Toc )₂ S were simply prepared under remarkably mild conditions with complete control of the regiochemistry by using δ-, γ-, and β-tocopheryl-N-thiophthalimides ( Toc-NSPht ) as common starting materials. The roles of sulfur atom(s), H-bond and aryl ring substitution pattern on the antioxidant profile of these new compounds, which were assembled by linking together two tocopheryl units, are also discussed.     

Formylation of alkyl cyanofurylmethanphosphonates at the active methylene group

Alkyl cyanofurylmethanephosphonates are formylated with ethyl formate in the presence of sodium foil to form sodium derivatives of phosphonoacetic aldehyde. If phosphonoacetic aldehyde and nitrile groups occupy remote positions in the furan ring, the sodium derivative in DMSO solution exists in the form of carbanion carrying charge on the carbon atom adjacent to the aldehyde group. If the substituents are located at the adjacent carbons of furan ring, the solution equilibrium between the carbanionic (major product) and Z-enolate forms of salts is established. Alkylation of the formed salts with methyl iodide occurs exclusively at the oxygen atom to give methyl enolates. In most cases, a mixture of E-and Z-isomers is formed, the E one being prevailing. In the case of 2,5-location of the substituents in furan ring, the sodium salt is inactive, and the alkylation does not occur.     

Synthesis and reaction of methylbenzo[a]quinolizinium salts

All isomers of (monomethyl)benzo[a]quinolizinium salts including five new monomethyl derivatives were prepared by photocyclization, sulfur extrusion, or cyclodehydration reaction, and their aldol-type condensation was examined. The 2- and 4-methyl derivatives 3b and 3c reacted with p-methoxybenzaldehyde in the presence of piperidine to yield trans-(p-methoxystyryl)benzo[a]quinolizinium salts 11 . The other methyl derivatives did not react with the aldehyde. The methyl group was reactive at the 2- and 4-positions, located para and ortho to the azonia ring nitrogen, respectively; however, it was unreactive at the 6-position located at another ortho position.