Unexpected Formation of Benzothiazoles in the Synthesis of New Heterocycles: Benzo-1,2,4-dithiazines
36
Citation
0
Reference
10
Related Paper
Citation Trend
Abstract:
The synthesis of benzo-1,2,4-dithiazines was investigated presuming a reversible sulfur-sulfur bond formation. 2-Aminothiophenol, when allowed to react with isothiocyanates, provided benzothiazoles. 2,2′-Diaminodiphenyl disulfide underwent cyclizations very readily without any reducing agent to give, according to the reaction conditions, benzothiazoles or benzo-1,2,4-dithiazines. The developed procedure offers a simple and convenient way to prepare the title compounds in very good to excellent yields. Until now, benzo-1,2,4-dithiazines as well as 2,2′-diaminodiphenyl disulfides bearing aminocarbonothioyl groups were unknown.Keywords:
Reaction conditions
Abstract A new scalable route to synthesize the factor Xa (FXa) inhibitor betrixaban is disclosed. The product is obtained in a seven-step reaction sequence (in five stages using two one-pot reactions) starting from easily accessible 4-(N,N-dimethylcarbamimidoyl)benzoate. Effective isolation of intermediates, use of cost-effective amide formation and 2-methyltetrahydrofuran as an effective reaction solvent as well as for extraction in three of the stages, are key features. The strategy provides the desired product in 38% overall yield with high purity (>98%).
Amide
Reaction conditions
Cite
Citations (0)
Cite
Citations (11)
The purple sulfur bacterium Allochromatium vinosum can use elemental sulfur as an electron donor for anoxygenic photosynthesis. The elemental sulfur is taken up, transformed into intracellular sulfur globules and oxidized to sulfate. Commercially available 'elemental' sulfur usually consists of the two species cyclo-octasulfur and polymeric sulfur. The authors investigated whether only one sulfur species is used or at least preferred when Alc. vinosum takes up elemental sulfur and forms globules. To this end, Alc. vinosum was cultivated photolithoautotrophically with two types of elemental sulfur that differed in their cyclo-octasulfur : polymeric sulfur ratio, as well as with pure polymeric sulfur. Sulfur speciation was analysed using X-ray absorption spectroscopy, and sulfate contents were determined by HPLC to quantify the amount of elemental sulfur being taken up and oxidized by Alc. vinosum. The results show that Alc. vinosum uses only the polymeric sulfur (sulfur chain) fraction of elemental sulfur and is probably unable to take up and form sulfur globules from cyclo-octasulfur. Furthermore, direct cell–sulfur contact appears to be necessary for uptake of elemental sulfur by Alc. vinosum.
Sulfur Cycle
Anoxygenic photosynthesis
Green sulfur bacteria
Cite
Citations (75)
X-ray absorption near edge structure (XANES) spectroscopy at the sulfur K-edge was applied to probe the speciation of sulfur of metabolically different sulfur-accumulating bacteria in situ. Fitting the spectra using a least-square fitting routine XANES reveals at least three different forms of sulfur in bacterial sulfur globules. Cyclooctasulfur dominates in the sulfur globules of Beggiatoa alba and the very recently described giant bacterium Thiomargarita namibiensis. A second type of sulfur globules is present in Acidithiobacillus ferrooxidans: here the sulfur occurs as polythionates. In contrast, in purple and green sulfur bacteria the sulfur mainly consists of sulfur chains, irrespective of whether it is accumulated in globules inside or outside the cells. These results indicate that the speciation of sulfur in the sulfur globules reflects the different ecological and physiological properties of different metabolic groups of bacteria.
XANES
Genetic algorithm
Cite
Citations (171)
XANES
Oxidizing agent
Cite
Citations (15)
The profile distribution of specific sulfur forms was examined in a Louisiana freshwater marsh. Soil samples were fractionated into acid-volatile sulfides (AVS), HCl-soluble sulfur, elemental sulfur (S°), pyrite sulfur (FeS2), ester-sulfate sulfur, carbon-bonded sulfur, and total sulfur. Inorganic sulfur constituted 14 to 30% of the total sulfur pool, with HCl-soluble sulfur present as the largest portion (77–94%). AVS sulfur accounted for <1% of total soil sulfur. No clear pattern of pyrite sulfur formation was observed in the upper 20 cm of the soil profile; however, concentration tended to increase with depth below this zone. Pyrite sulfur represented <3% of total sulfur and together with elemental sulfur accounted for 6 to 21% of the inorganic sulfur fraction. Elemental sulfur concentration was highest in the plant root zone (<20-cm). Organic sulfur in the forms of ester-sulfate sulfur and carbon-bonded sulfur was a major constituent (70–86%) of total sulfur. Ester sulfate represented between 15 and 34% of the organic sulfur fraction.
Sulfur Cycle
Cite
Citations (10)
Abstract Titanocenedicarbonyl, Cp2Ti(CO)2, activates the sulfur-sulfur bond in organic disulfides and sulfur homocycles like S6S7 and S8- Cyclic disulfides form chelating ligands with sulfur atoms attached to the Ti atom. The reaction with S6 yields a new compound with an eight sulfur atoms containing ligand. The novel titanocene compounds have been used as precursors for the synthesis of a series of methylene polysulfides.
Methylene
Cite
Citations (16)
A new and efficient synthetic methodology has been developed to prepare azepino[4,5-b ]indole derivatives under Brønsted acid catalysis.
Simplicity
Reaction conditions
Cite
Citations (18)
Abstract Available sulfur was determined in a greenhouse experiment with 30 surface soils from the Southeastern United States by growing cotton plants at six levels of applied sulfate‐sulfur, 0, 2, 4, 8, 16, and 32 ppm. The A value technique involving radiosulfur was used as an index of available sulfur. Sulfur A values varied from 9.8 ppm. to 42 ppm. A high degree of correlation was obtained between A values and the percent sulfur in the control plants. Growth responses from applied sulfate‐sulfur were also related to percent sulfur in the control plants and to A value sulfur in the soil. The total uptake of sulfur also was related closely to the total available sulfur in the soil ( A value plus fertilizer sulfur). A sixteen‐fold increase in the rate of sulfur addition increased the A value by approximately 20%.
Sulfur Cycle
Cite
Citations (9)