Nitrogen and Sulphur Heterocycles

Nitrogen and Sulphur Heterocycles.—Investigations of the cationic polymerizations of nitrogen and sulphur heterocycles have been conducted principally by Goethals and his co-workers. Recent kinetic studies have yielded rate con- 

Brzezinska, W. Chwialkowska, P. Kubisa, K. Matyjaszewski, and S. Penezek, Makromol CAem., 1977,178,2491. 

Simonds, H. Muythen, and E. J. Goethals, (Preprints), 1st European Discussion Meeting on Polymer Science, Strasbourg, 1978, 106. 

Subsequent cleavage at the sulphonium groups through intramolecular Snl attack leads to the formation of cyclic oligomers. 

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The most stable oils are the paraffmics because of their ability to resist oxidative attack. The oxidative instability of an oil is related to the presence or otherwise of polar structures, such as nitrogen and sulphur heterocyclic structures. The higher the aromaticity of an oil, the worse will be its resistance to oxidation. 

Acid and base extractions from this material have been shown to form spontaneous structures in solution termed coercevates that could easily form the basis for protypical membranes (more of this in Chapter 9). Hydrocarbons with chain lengths C15-C30 (both straight and branched chains) and of course PAHs, predominantly pyrene and fluoranthrene, polar hydrocarbons such as aromatic ketones, alkyl and aryl ketones, nitrogen and sulphur heterocycles and most intriguingly purine and pyrimidine analogues have all been observed from this rich carbonaceous cocktail of compounds. Why ... 

Aqueous concentrations of hydrophobic organics such as polyaromatic hydrocarbons (PAH), compounds such as nitrogen and sulphur heterocyclic PAHs, and some substituted... 

C18 Reversed phases are not necessarily limited to polycyclic and halogenated (or nitrated) hydrocarbons, but can be used for a number of oxygen-, nitrogen- and sulphur- containing heterocyclic compounds in a similar way to that used in reversed-phase chromatography. In this context, ref. 185 describes the separation of compounds of this category. A plethora of similar separations can be found in the Section devoted... 

Cf. L. L. Bambas, Five-Membered Heterocyclic Compounds with Nitrogen and Sulphur or Nitrogen, Sulphur or Nitrogen, Sulphur and Oxygen, Interscience, New York, 1982. 

Parts 2 and 3 of the comprehensive review of the chemistry of thiazole have appearedthese include chapters on meso-ionic thiazoles and on cyanine dyes derived from thiazolium salts, and also one on selenazole and its derivatives. The chemistry of selenazole is also included in a review of selenium-nitrogen heterocycles. An account of the chemistry of thiazolidin-4-ones (which includes 2,4-diones but not rhodanine and isorhodanine) updates an earlier review. Reviews on cyclic sulphur-nitrogen compounds and on the synthesis and transformations of nitrogen- and sulphur-containing bicyclic heterocycles have appeared. More general reviews, which contain chemistry relevant to this section, cover reactions based on the onium salts of aza-aromatics, the synthesis of... 

N-oxidation and S-oxidation, This can be used for heterocyclic nitrogen and sulphur compounds. Oxidising agents could include hydrogen peroxide, bromine and chloroperbenzoic acid. A good example would be the oxidation of electroinactive chlor-promazine to its electroactive S-oxide. 

In recent years, with the development of rotating-bomb calorimetry and the refinement of thermodynamic corrections for the combustion process for nitrogen and sulphur containing organic compounds, a number of accurate heats of combustion of heterocyclic compounds have been determined. 

Rapoport and co-workers have reported a general synthesis of nitrogen, oxygen, and sulphur heterocycles (218) by rhodium-catalysed intramolecular N-H, 0-H, or S-H insertion reactions.of keto-ester precursors (217)- This reaction is well documented as an efficient route to B-lactams but this group has now shown that the reaction works well for the synthesis of five-and six-membered nitrogen heterocycles (Scheme 22). The reaction fails for seven-membered nitrogen heterocycles in this case C-H insertion to give a eyelopentanone is the preferred reaction mode. 

Flash vacuum pyrolysis (625 °C 0.1—1 Torr) of 2,3-benzoxazin-l-one (328) produces biphenylene (7%) and 2-phenyl-3,l-benzoxazin-4-one (320 R = Ph) (11%) rather than the hoped-for benzazete-derived products. The azirino-a-lactone (329) has been suggested as a possible reaction intermediate. The gas-phase thermal and photochemical decompositions of nitrogen, oxygen, and sulphur heterocycles have been reviewed. 

In addition to benzenoid diazo components, diazotised heterocyclic amines in which the amino group is attached to a nitrogen- or sulphur-containing ring figure prominently in the preparation of disperse dyes [87,88], since these can produce marked bathochromic shifts. The most commonly used of these are the 6-substituted 2-aminobenzothiazoles, prepared by the reaction of a suitable arylamine with bromine and potassium thiocyanate (Scheme 4.31). Intermediates of this type, such as the 6-nitro derivative (4.79), are the source of red dyes, as in Cl Disperse Red 145 (4.80). It has been found that dichloroacetic acid is an effective solvent for the diazotisation of 2-amino-6-nitrobenzothiazole [89]. Subsequent coupling reactions can be carried out in the same solvent system. Monoazo disperse dyes have also been synthesised from other isomeric nitro derivatives of 2-aminobenzothiazole [90]. Various dichloronitro derivatives of this amine can be used to generate reddish blue dyes for polyester [91]. 

Heal, H. G. The Inorganic Heterocyclic Chemistry of Sulphur, Nitrogen and Phosphorus, Academic Press, London 1980... 

Isoxazole, pyrazole and isothiazole constitute the 1,2-azole family of heterocycles that contain two hetero-atoms, one of which is a nitrogen atom. The second hetero-atom is oxygen, nitrogen or sulphur, respectively. 

Unlike our initial imine disconnection which is restricted to nitrogen heterocycles (with one or two specific exceptions such as pyrylium salts, see Chapter 9), the heteroatom in the enamine or enamine-like disconnection could be divalent. Therefore this disconnection is also applicable to oxygen-and sulphur-containing heterocycles, typified by 1.24 and 1.25. 

Other miscellaneous additions have been reported. Novel three-, five-, and six-membered nitrogen-sulphur heterocycles have been prepared by irradiation of sulphur monochloride in the presence of perfluoroazoalkanes. Photoaddition of hydrogen sulphide to the diallylsilane (232) yields the thiol (233), which readily undergoes cyclization to the l-thia-5-silacyclooctane (234). ... 

There were relatively few studies of n compounds possessing two PC bonds. They included a phosphindoline-3-one, a phosphinic acid, two nitrogen-sulphur heterocycles, two imidophosphinic acid derivatives, and a cyclo-triphosphazene. ... 

In general nitrogen-, phosphorus- and sulphur-containing enamines are much sought after, since they are important intermediates in heterocyclic synthesis. Preparation of B-substituted... 

Four-membered Rings containing Sulphur, Nitrogen, and Phosphorus.— The compound (160) results from the reaction of (155 R=p-anisyl) and (McjSOjNMe. Heterocycle (161) is obtained from isocyanates and (162). Thionyl chloride reacts with (163) to give (164). ... 

Treatment of sodium phenylacetylide with tellurium in DMSO gave the ditelluroles (217). Thermolysis of the easily available spirocyclic tellurans (218) afforded cyclic bis (disulphides) in good yields. The first heterocycles to contain sulphur, nitrogen, and tellurium, e.g. (219), have been obtained by the reaction of the intermediate 1,3-thiazabuta-1,3-dienes with SbjTej. Proton and C n.m.r. spectra of telluran-3,5-diones have been reported. ... 

Synthesis of Thiadiazoles.— The use of S4N4 in the preparation of nitrogen-sulphur heterocycles (see Vol. 5, pp. 104, 345) has been extended in that it has now been shown that its reaction with, for example, methyl propiolate in toluene, under reflux, yields mainly the 1,2,5-thiadiazole (132), with lesser amounts of the 1,2,4- and... 

As distinct from benzene and other ring systems which contain carbon as the only ring constituent are a number of heterocyclic ring compounds in which one or more of the carbons is replaced by an oxygen, nitrogen or sulphur atom. These too may be either saturated or unsaturated. 

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