Sulfur heterocycles

In the synthesis of commercial sulfur-heterocycles two interesting reactions are used (i) diphenylamines may be connected by a sulfur bridge in the orfho-positions (ii) the amino grouping of sulfonamides undergoes condensation reactions with neighboring imino- and amide groups. 

Condensa.tlon, This term covers all processes, not previously iacluded ia other process definitions, where water or hydrogen chloride is eliminated ia a reaction involving the combination of two or more molecules. The important condensation reactions are nitrogen and sulfur heterocycle formation, amide formation from acid chlorides, formation of substituted diphenyl amines, and misceUaneous cyclizations. 

A few special syntheses of thiirane derivatives from four-membered sulfur heterocycles are known. Methylenethiiranes are derived by thermolysis of the tosylhydrazones of thietan-3-ones (Scheme 143) (81TL4815), and 2,2,3,3-tetrakis(trifluoromethyl)thiirane is obtained by thermolysis of 2,2,4,4-tetrakis(trifluoromethyl)-l,3-dithietane 1,1-dioxide with loss of sulfur dioxide. 2,2,3,3-Tetrakis(trifluoromethyl)thiirane 1,1-dioxide is obtained in low yield by heating a mixture of 3,3-bis(trifluoromethyl)-l,2,4-oxadithietane 2,2,4,4-tetroxide and bis(trifluoromethyl)ketene. The mono-episulfide of norbornadiene is obtained from thietane derivative (65 Scheme 144) (73JOC649). 

Thiamin, or vitamin Blf contains a positively charged five-membered nitrogen-sulfur heterocycle called a thiazoliwn ring. Explain why thethiazolium ring is aromatic. 

A heterocycle is a cyclic compound that contains atoms of two or more elements in its ring, usually carbon along with nitrogen, oxygen, or sulfur. Heterocyclic amines are particularly common, and many have important biological properties. Pyridoxal phosphate, a coenzyme sildenafil (Viagra),... 

Kuhn EP, JM Suflita (1989) Microbial degradation of nitrogen, oxygen and sulfur heterocyclic compounds under anaerobic conditions studies with aquifer samples. Environ Toxicol Chem 8 1149-1158. 

Some nitrogen and sulfur heterocyclic systems produced in roasted coffee. 

In this article, a description has been given of recent investigations in the field of thiepin chemistry which are important for the major seven-membered unsaturated heterocyclic compounds. While the properties of these sulfur heterocycles have been determined quite well, some important questions still remain unexplored. Our current research efforts involve attempts to understand more generally the substituent effects on the thermal stability of the thiepin. 

In an earlier study the authors proposed a [3.2.0] bicyclic sulfonium salt 8 as the reactive intermediate in the trimethylsilyl iodide mediated ring contraction of 4-methoxythiephane <1996T5989>. Enantiomerically pure thio-lane derivatives were synthesized via a ring contraction of a seven-membered sulfur heterocycle by nucleophilic transannular substitution <2000TA1389>. The thiepane derivative 15, derived from d-sorbitol, was converted into the dimesyl derivative 16 following deprotection under acidic conditions. Treatment of 16 with sodium azide in DMSO at 120°C yielded the corresponding thiolane as a mixture of two diastereoisomers, 17a and 17b, in a 5 1 ratio (see Scheme 1). 

It has been claimed that biodesulfurization via the 4S pathway can also reduce viscosity. An application introduced by Environmental Bioscience Corporation included a method for reducing the viscosity of liquid-containing sulfur heterocycles [406] using biodesulfurization. The original patent application (Ser. No. 631642) was filed in US... 

Some enzymes have been found to be capable of conversion of the polyaromatic sulfur heterocycles in mixtures of an aqueous phase containing buffer+water-miscible solvent and a water-immiscible solvent. For example, conversion of thiophenes and sulfides was demonstrated in an aqueous system with 20% acetonitrile in contact with 0.2% diesel. A process for sulfur removal was designed based on this reaction [394], Additional details were given in Section 4.2.1. In a subsequent study effect of this system on PAH... 

In the approach followed in this invention [29], a biocatalytic agent converts the sulfur heterocycles into different molecules that do not exhibit the hydrophobic interactions. This is achieved by selectively cleaving carbon-sulfur bonds. The selectivity of the biocatalytic agent employed is limited to the carbon-sulfur bonds and no attack to the carbon-carbon skeleton was reported. Thus, it is expected that the proposed biocatalytic reduction of viscosity would not diminish the fuel value of the treated petroleum liquids. The biocatalyst employed consisted of the strain ATCC No. 53968 (see Section 20 and references therein), in an aqueous culture conventionally prepared by fermentation under aerobic conditions. The fermenting bioreactor is fed with a suitable nutrient medium, which comprises a conventional carbon source (dextrose and glycerol are recommended carbon sources. To confer maximal biocatalytic activity for the desired cleavage of organic C—S bonds, the bacteria was kept in a state of sulfur deprivation. 

The research was oriented towards the development of biocatalysts for removal of recalcitrant sulfur heterocyclic compounds including benzothiophenes, naphthothio-phenes, and alkylbenzothiophenes. To begin with, they focused on asymmetric sulfur compounds in this class and developed a method for desulfurization of these compounds present in petroleum products [108], The identity of the microorganisms was not disclosed in the abstract but they do claim use of the enzymes as well in the application. 

Thionyl chloride (SOCl2) is the most versatile of all sulfur transfer reagents in heterocyclic synthesis. The sulfur-oxygen bond renders the sulfur atom more electrophilic the possibility of ready removal by elimination of the oxygen atom allows easy aromatization of many of the initially formed sulfur heterocycles. Two general reviews of the chemistry of thionyl chloride are available.53 Both cover the literature up to about 1970. 

Gimeno R.A. et al., 2002. Determination of polycyclic aromatic hydrocarbons and polycyclic aromatic sulfur heterocycles by high-performance liquid chromatography with fluorescence and atmospheric pressure chemical ionization mass spectrometry detection in seawater and sediment samples. J Chromatogr A 958 141. 

Intramolecular cyclization of 2-lithiobenzyl-2-halophenyl amines, ethers, and thioethers—Synthesis of phenanthridine, dibenzopyran, and dibenzothiopyran derivatives Having demonstrated the efficiency of this methodology for the preparation of indole derivatives, we prepared the 2-fluoro-phenyl ether and thioether 22 a, b to study their potential as substrates that could afford oxygen and sulfur heterocycles. However, treatment of 22 a, b with fBuLi afforded, after... 

Few examples have been reported of metals coordinated to six-membered boron-sulfur heterocycles. Ashe et al. prepared 4-methyl-l,4-thiaborin (SC4H4BMe) which forms a stable molybdenum tricarbonyl sandwich complex 144.158 jn g etjert s laboratory, the reaction of the diborolyl complex 33 (Section 3.01.3.2) with COS afforded the dinuclear complex 145 whose structure was determined crystallographically.36 Other products, not involving boron-sulfur heterocycles and hence outside the scope of this discussion, were obtained via the treatment of 33 with different sulfur reagents such as CS2.36... 

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