Oleg A. Rakitin

Breaking the Mold of Discotic Liquid Crystals

Small molecules of the indene and pseudoazulene type like 1 and 2 form columnar mesophases! These compounds do not possess peripheral flexible chains like conventional columnar liquid crystals. Instead, polarizable chlorine and sulfur atoms, as well as the polar cyano group, function as unusual soft regions between the rigid columns.

EIN NEUES BAUPRINZIP FUR DISKOTISCHE FLUSSIGKRISTALLE

Kleine Molekule vom Inden- und Pseudoazulentyp wie 1 bzw. 2 bilden kolumnare Mesophasen! Diese Verbindungen haben keine endstandigen flexiblen Ketten, wie sie sonst bei entsprechenden Mesogenen vorhanden sind, sondern polarisierbare Chlor- und Schwefelatome oder eine polare Cyanogruppe, die als ungewohnliche „weiche” Bereiche zwischen den saulenformigen Stapeln fungieren.

One-pot synthesis of 5-phenylimino, 5-thieno or 5-oxo-1,2,3-dithiazoles and evaluation of their antimicrobial and antitumor activity

We here report the synthesis and biological evaluation of rare 4-substituted-5-phenylimino, 5-thieno- and 5-oxo-1,2,3-dithiazoles. Dithiazoles were selectively obtained in moderate to high yields (25-73%) via a one-pot reaction from various ethanoneoximes with sulfur monochloride, pyridine in acetonitrile followed by treatment by corresponding nucleophiles (aniline, thioacetamide and formic acid). All the synthesized compounds were screened for their antibacterial (against bacteria Escherichia coli, Salmonellaenterica serovar Typhimurium, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, Enterococcus faecalis, Bacillus cereus and Listeria inocua), antifungal (against pathogenic strains Candida albicans, Candida glabrata, Candida tropicalis and Issatchenkia orientalis) and antitumor (on human cell lines MCF-7 and MDA-MB-231) activity. 4-(2-Pyridinyl)-5H-1,2,3-dithiazole-5-thione and 4-ethylcarboxyl-5H-1,2,3-dithiazole-5-thione (5d, 5h) that are active against Gram-positive bacteria are significantly active against fungi. 4-(2-Benzofuranyl)-5-phenylimino-5H-1,2,3-dithiazole (4e) exerts antiproliferative activity.

A one-step synthesis of fused pentathiepinsElectronic supplementary information (ESI) available: characterization of compounds 2–5, 9, and 11. See http://www.rsc.org/suppdata/cc/b2/b203349f/

Treatment of nucleophilic heterocycles like pyrroles and thiophene, and their tetrahydro derivatives, with S2Cl2 and a base in chloroform at room temperature provides a simple one-pot synthesis of heterocyclic fused mono and bis pentathiepins such as 2, 3, 4, 5, 9, and 11.

Direct synthesis of fused 1,2,3,4,5-pentathiepins

Treatment of nucleophilic heterocycles like pyrroles and thiophenes, and their tetrahydro derivatives, with S2Cl2 and DABCO in chloroform at room temperature provides a simple one-pot synthesis of fused mono and bispentathiepins. N-Methylpyrrole and its 2-chloro and 2,5-dichloro derivatives and N-methylpyrrolidine all give the same dichloropentathiepin 1a. N-Ethyl, isopropyl and tert-butylpyrrolidine behave similarly; the isopropylpyrrolidine also gives the bispentathiepin 6which undergoes an intriguing rearrangement to the symmetrical monopentathiepin 1c. N-Methyl and ethyl indole give either 2,3-dichloro derivatives 8 or the pentathiepinoindoles 9, depending upon the reaction conditions. Thiophene and tetrahydrothiophene give the pentathiepin 10. X-Ray crystal structures are provided for the pentathiepins 1a and 1d, and possible reaction pathways are suggested for the extensive cascade reactions reported.

Direct synthesis of 2-cyanobenzimidazoles and the generation of S2

2-Cyanobenzimidazoles 6 are readily prepared from 1,2-diaminobenzenes 4 and 4,5-dichloro-1,2,3-dithiazolium chloride 1, either directly or through thermal or acid-catalysed rearrangement of the isolated imine intermediates 5; thermolysis of the imine 5b at 140–150°C simultaneously generates diatomic sulfur, S2, as shown by its interception.

Chapter 4 Sulfur Monochloride in the Synthesis of Heterocyclic Compounds

Publisher Summary The reactions described in this chapter explain that sulfur monochloride is an important reagent for the synthesis of heterocycles with various numbers of sulfur atoms and even without sulfur. An important feature of this reagent is that it can add not only two sulfur atoms to the molecule, as might be expected, but also one, three, four, five, or even more atoms and the structure of the final compound often depends on its stability. The recent developments in the use of sulfur monochloride include: the discovery of its ability to form complexes with organic bases and of the significant difference in reactivity of these complexes from S2Cl2. A selective synthesis of particular heterocycles require accurate conditions like temperature, solvent, catalyst, and base.

Recent Developments in the Synthesis and Applications of 1,2,5-Thia- and Selenadiazoles. A Review

1,2,5-Chalcogenadiazoles (oxa-, thia-, selena-, and telluradiazoles) have been known for many years. Their first representative, 2,1,3-benzothiadiazole (1), was discovered in 1889 by Hinsberg.1 Not...

Bis(toluene)chromium(I) [1,2,5]Thiadiazolo[3,4-c][1,2,5]thiadiazolidyl and [1,2,5]Thiadiazolo[3,4-b]pyrazinidyl: New Heterospin (S1 = S2 = 1/2) Radical-Ion Salts

Bis(toluene)chromium(0), Cr(0)(η(6)-C7H8)2 (3), readily reduced [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (1) and [1,2,5]thiadiazolo[3,4-b]pyrazine (2) in a tetrahydrofuran solvent with the formation of heterospin, S1 = S2 = ½, radical-ion salts [3](+)[1](-) (4) and [3](+)[2](-) (5) isolated in high yields. The salts 4 and 5 were characterized by single-crystal X-ray diffraction (XRD), solution and solid-state electron paramagnetic resonance, and magnetic susceptibility measurements in the temperature range 2-300 K. Despite the formal similarity of the salts, their crystal structures were very different and, in contrast to 4, in 5 anions were disordered. For the XRD structures of the salts, parameters of the Heisenberg spin Hamiltonian were calculated using the CASSCF/NEVPT2 and broken-symmetry density functional theory approaches, and the complex magnetic motifs featuring the dominance of antiferromagnetic (AF) interactions were revealed. The experimental χT temperature dependences of the salts were simulated using the Van Vleck formula and a diagonalization of the matrix of the Heisenberg spin Hamiltonian for the clusters of 12 paramagnetic species with periodic boundary conditions. According to the calculations and χT temperature dependence simulation, a simplified magnetic model can be suggested for the salt 4 with AF interactions between the anions ([1](-)···[1](-), J1 = -5.77 cm(-1)) and anions and cations ([1](-)···[3](+), J2 = -0.84 cm(-1)). The magnetic structure of the salt 5 is much more complex and can be characterized by AF interactions between the anions, [2](-)···[2](-), and by both AF and ferromagnetic (FM) interactions between the anions and cations, [2](-)···[3](+). The contribution from FM interactions to the magnetic properties of the salt 5 is in qualitative agreement with the positive value of the Weiss constant Θ (0.4 K), whereas for salt 4, the constant is negative (-7.1 K).

New route to 2-cyanobenzimidazoles

Abstract N-Monosubstituted 1,2-diaminobenzenes 4 (RMe, Ph, PhCH2, and 3,4-Me2C6H3CH2) react with 4,5-dichloro-1,2,3-dithiazolium chloride 1 in dichloromethane at room temperature to give the corresponding 2-cyanobenzimidazoles 6. If pyridine is added at the beginning of the reaction, the intermediate imino-1,2,3-dithiazoles 5 can be isolated. Upon thermolysis, most of the imines 5 give the 2-cyanobenzimidazoles 6 in fair to good yields. 1,2-Diaminobenzene can be converted in high yield into the mono-imine 5i or the bis-imine 12, RH; thermolysis of 5i gives 2-cyanobenzimidazole in high yield. Conversion of 5 into 6 involves the loss of both sulfur atoms and with the N-phenylimino derivative 5b singlet diatomic sulfur, S2, has been intercepted with norbornene and with 2,3-diphenylbutadiene to give the expected cycloadducts 7 and 8.