L. K. Papernaya

Stereochemical behavior of 77Se‐1H spin‐spin coupling constants in pyrazolyl‐1,3‐diselenanes and 1,2‐diselenolane

Conformational study of five derivatives of 2‐(pyrazol‐4‐yl)‐1,3‐diselenane together with related 1,2‐diselenolane in respect to the stereochemical trends of geminal and vicinal 77Se‐1H spin‐spin coupling constants has been carried out by means of high‐level theoretical calculations in combination with experiment. The marked dihedral angle dependences for both types of couplings accounted for the lone pair effect in the case of geminal coupling constants and the Karplus‐type relationship for vicinal couplings have been established, which is of major importance for the stereochemical analysis of saturated selenium containing heterocycles. Copyright

Synthesis and reactions of pyrazole-4-carbaldehydes

Abstract1-, 3-, and 5-Alkylpyrazoles, as well as linearly bridged bis-pyrazoles, were converted into the corresponding 4-formyl derivatives by Vilsmeier-Haak reaction both under standard conditions and under microwave activation in DMF over a period of 10 min. 1,1′-(Hexane-1,6-diyl)bis(3,5-dimethyl-1H-pyrazole) and 1,1′-(benzene-1,4-diyldimethylene)bis(3,5-dimethyl-1H-pyrazole) gave rise to 4-formyl derivatives at both pyrazole rings. 5-Chloro-1,3-dialkyl-1H-pyrazoles failed to undergo formylation according to Vilsmeier-Haak or under microwave activation. 1,1′-Bridged bis-3,5-dimethyl-1H-pyrazoles reacted with 2-sulfanylethanol on heating in the presence of chloro(trimethyl)silane to give the corresponding bridged bis-4-(1,4,6-oxadithiocan-5-yl)-1H-pyrazoles.

Synthesis of Open-Chain Dithioacetals from Thiophene-2-carbaldehyde and Its Analogs

A procedure for the synthesis of dithioacetals containing various thiophene fragments was developed on the basis of the reaction of thiophene-2-carbaldehyde and its analogs with thiols in chlorotrimethylsilane.

New approach to the synthesis of cyclic 1,3-dithioacetals from thiophene-2-carbaldehydes

A highly selective method was developed for preparation of previously unknown 1,3-dithiolanes and 1,3-dithianes by reactions of thiophene-2-carbaldehyde and its analogs with alkanedithiols under the action of trimethylchlorosilane.

Synthesis of the thiophene series 1,3-diselenanes

Direct reaction of propan-1,3-diselenol with thiophene-2-carbaldehydes in trimethylchlorosilane medium is studied. Synthetic procedure for preparation of the previously unknown 1,3-diselenanes of thiophene series is developed. Structure of the newly obtained compounds is established by 1H, 13C, and 77Se NMR spectroscopy. Chromatomass spectrometric stidy of the products obtained is carried out. In some cases reaction may be directed to the synthetis of new types of polymers of original structure.

Microwave-assisted synthesis of 2,5-diarylthiazolo[5,4-d]thiazoles from benzaldehydes and dithiooxamide

One-pot condensation of dithiooxamide with aromatic aldehydes and subsequent oxidation of intermediate 2,5-dihydro[1,3]thiazolo[5,4-d][1,3]thiazoles with selenium dioxide afforded 2,6-diaryl[1,3]thiazolo-[5,4-d][1,3]thiazoles which were characterized by 1H and 13C NMR, IR, and X-ray diffraction data.

Synthesis and properties of pyrazole carbaldehyde bis(2-hydroxyethyl)-dithioacetal hydrochlorides*

A simple method has been developed for the synthesis of water-soluble pyrazole derivatives, namely 4-[bis(2-hydroxyethylsulfanyl)methyl]pyrazoles hydrochlorides, by the reaction of a series of pyrazole carbaldehydes with 2-mercaptoethanol in the presence of trimethylchlorosilane. When treated with aqueous ammonia solution the pyrazole-4-carbaldehydes bis(2-hydroxyethyl)dithioacetal hydro-chlorides are converted to the 4-[bis(2-hydroxyethylsulfanyl)methyl]pyrazole free bases.

Synthesis of the first representative of 2-pyrazolyl-1,3-diselenanes, 3,5-dimethyl-1-(prop-2-en-1-yl)-4-(1,3-diselenan-2-yl)-1H-pyrazole

Selenoacetals are used as reagents in organic synthesis, and they play a significant role in the development of organoselenium chemistry [1–4]. Up to now, a few selenoacetals derived from cyclic carbaldehydes have been reported [1–10]. The known methods for the preparation of selenoacetals are multistep and laborious, and their scope is restricted by accessibility and stability of initial selenols. For example, the synthesis of 1,3-diselenanes has not received wide application due to difficult preparation and extreme instability of propane-1,3-diselenol and its substituted derivatives. Propane-1,3-diselenol reacts with aliphatic aldehydes in strongly acidic medium [8, 9], and only reactions of propane-1,3-diselenol and its substituted derivatives with benzaldehyde and some aliphatic aldehydes occur under milder conditions, in the presence of ZnCl2 [1–3, 10]. Prior to our studies hetaryl-1,3-diselenanes were unknown. We previously synthesized 2-(1,3-diselenan2-yl)thiophenes in 12–57% yield from propane-1,3-diselenol and thiophenecarbaldehydes [11]. Even under mild conditions (–3 to –5°C, Me3SiCl as catalyst) these reactions were accompanied by oligomerization. In the present communication we report for the first time on the reaction of 1-allyl-3,5-dimethyl-1H-pyrazole-4-carbaldehyde (I) with propane-1,3-diselenol (II) in the presence of Me3SiCl. The reaction direction was not obvious. For example, pyrazolecarbaldehydes reacted with 2-sulfanylethanol in the presence of Me3SiCl to give mainly open-chain bis(2-hydroxyethyl) dithioacetals even at an equimolar reactant ratio [12], in contrast to analogous reactions of aromatic aldehydes [13]. We have found that the reaction of aldehyde I with propane-1,3-diselenol (II) in Me3SiCl at room temperature yields only 1-allyl-4-(1,3-diselenan-2-yl)-3,5dimethyl-1H-pyrazole which was isolated as hydrochloride III. Neither open-chain bis(3-selanylpropyl) diselenoacetals nor addition products of diselenol II at the allyl group of pyrazolecarbaldehyde I were detected. Owing to protonation of the N atom, signals from methyl protons in the H NMR spectrum of hydrochloride III are broadened and displaced downfield relative to the corresponding signals of free base IV. Furthermore, the 3-Me signal appears in a weaker field relative to the 5-Me signal. Protonation of the N atom makes its resonance more upfield by 80–90 ppm. Hydrochloride III was converted into free base IV during chromatography on silica gel. According to the H NMR data, the six-membered 1,3-diselenane ring adopts a chair conformation with equatorial orientation of the pyrazolyl substituent. Propane-1,3-diselenol (II) was prepared by reductive cleavage of the Se–Se bond in poly(trimethylene diselenide) in the system N2H4 · H2O–KOH [14]. 4-(1,3-Diselenan-2-yl)-3,5-dimethyl-1-(prop-2en-1-yl)-1H-pyrazole hydrochloride (III). Propane1,3-diselenol (II), 0.404 g (2 mmol), was added dropwise under stirring at room temperature to a solution of 0.328 g (2 mmol) of pyrazolecarbaldehyde I in 1.304 g (12 mmol) of Me3SiCl. The reaction was complete in 5 min and was accompanied by heat evolution. The reaction mixture divided into two layers. The viscous material was separated from the liquid part by decanting, washed with hexane, and dried under reduced ISSN 1070-4280, Russian Journal of Organic Chemistry, 2012, Vol. 48, No. 9, pp. 1259–1260.

A polysulfide based on bis(thien-2-yl)sulfide : Synthesis and testing as an active cathode material

A reaction of the polycondensation product of bis(thien-2-yl)sulfide and formaldehyde with elemental sulfur affords a polymer containing polysulfide moieties (S-content = 67.2%). When used as active cathode material for model lithium rechargeable cells, the polymer shows the discharge capacity of 620 mA·h· g−1 at the first cycle.

5-(2-Thienylsulfanyl)thiophene-2-carbaldehyde: Thioacetalization, chloromethylation, and oxidation

Abstract5-(2-Thienylsulfanyl)thiophene-2-carbaldehyde reacted with propane-1-thiol and propane-1,3-dithiol in the presence of chloro(trimethyl)silane to give previously unknown 5-[bis(propylsulfanyl)methyl]-2-(2-thienylsulfanyl)thiophene and 2-[5-(2-thienylsulfanyl)thiophen-2-yl]-1,3-dithiane. Chloromethylation of 5-(2-thienylsulfanyl)thiophene-2-carbaldehyde with formaldehyde in a stream of hydrogen chloride in the presence of zinc chloride resulted in the formation of an oligomeric product consisting of thiophene rings connected alternately by sulfur and methylene bridges. The oligomer is formed via fast polycondensation of the primary chloromethylation product with the initial aldehyde. 5-(2-Thienylsulfanyl)thiophene-2-carbaldehyde was oxidized at the sulfide and aldehyde groups with 30% hydrogen peroxide in glacial acetic to produce 5-(2-thienylsulfonyl)thiophene-2-carboxylic acid.