Heterocyclic sulphoxides

Oxidation of a thiiraneradialene with equimolar amounts of MCPBA in CH2C12 at about 0°C gave the corresponding thiiraneradialene S-oxide 26 in a quantitative yield47 (equation 11). 5-Membered heterocyclic sulphoxides such as 1,3-benzoxathiolane sulphoxide 27, 1,3-benzdithiolane sulphoxide 28 and 1,3-dithiolane sulphoxide 29 were readily obtained from their sulphide precursors by oxidation with MCPBA in dich-loromethane solution48. 

Heterocyclic sulphoxides of general structure 185,186 and 187 have been prepared by cycloaddition of diarylsulphines 173b to nitrile oxides 188226, nitrile ylides 189227 and nitrones 190228, respectively (equation 100). 

Heterocyclic sulphoxides 65 mass spectra of 130-132 Hexahydronaphthalenols, synthesis of 310 Hofmann elimination 953 HOMO energies 1048, 1049 Homolytic substitution 1109 intramolecular 846 Horner-Wittig reaction 333 Hot electrons 892, 893 HSAB theory 282, 549 Hydrides, as reducing agents 934-941, 959 Hydrogen abstraction, photochemical 874, 876, 877, 879, 880... 

N— compounds used as acid inhibitors include heterocyclic bases, such as pyridine, quinoline and various amines. Carassiti describes the inhibitive action of decylamine and quinoline, as well as phenylthiourea and dibenzyl-sulphoxides for the protection of stainless steels in hydrochloric acid pickling. Hudson e/a/. refer to coal tar base fractions for inhibition in sulphuric and hydrochloric acid solutions. Good results are reported with 0-25 vol. Vo of distilled quinoline bases with addition of 0 05m sodium chloride in 4n sulphuric acid at 93°C. The sodium chloride is acting synergistically, e.g. 0-05m NaCl raises the percentage inhibition given by 0-1% quinoline in 2n H2SO4 from 43 to 79%. Similarly, potassium iodide improves the action of phenylthiourea . 

DNBLeu (covalent).5 Chiral phases S-Asp-artyl-S-phenylalanine methyl ester, N.N- Di-propyl-S-alanine cupric acetate. Phosphonates, aryl-sulphoxides, nitrogen heterocycles, di-B-naphthols. 

Aromatic and heterocyclic nitro compounds are readily reduced in good yield to the corresponding amines (e.g. o-aminophenol, Expt 6.50) by sodium borohydride in aqueous methanol solution in the presence of a palladium-on-carbon catalyst. In this reduction there is no evidence for the formation of intermediates of the azoxybenzene or azobenzene type, although if the reaction is carried out in a polar aprotic solvent, such as dimethyl sulphoxide, azoxy compounds may sometimes be isolated as the initial products. 

The reaction of sulphides with (dichloroiodo)benzene can lead to several kinds of products depending on the substrate and the reaction conditions [19]. Sulphides of great structural diversity (aliphatic, aromatic, heterocyclic) were oxidized efficiently by (dichloroiodo)benzene (one equivalent) in aqueous pyridine. The reaction was almost instantaneous and not noticeably sensitive to steric or electronic effects. Ethylenic double bonds were not attacked under these conditions however, in vinylic sulphides containing an electron-withdrawing group (COOH or RSO) ft- to the sulphur atom the oxidation was accompanied by nucleophilic attack to the double bond resulting in a mixture of products. The method is suitable for the preparation of I80-labelled sulphoxides using small quantities of H2,80. 

Carboxin was much more readily photodegraded than oxycarboxin in pure water. The oxidation of the sulphur atom yielded the sulphoxide Va and the subsequent loss of the heterocyclic ring produced the oxanilic acid Vb (see Scheme 6). Humic substances enhanced the phototransformation of both fungicides. For carboxin, this enhancement is possibly related to the presence of the sulphur atom that might be oxidized by singlet oxygen or other photo-oxidants. 

From Other Sulphur Heterocycles. The diazo-ketone (24), prepared from 27f-thiopyran-3(6//) Oi c and phenyl azide, yields (25) upon heating, which apparently is the stable tautomer of 3-hydroxy-4-phenylaminomethylthiophen, and (26). The structures of both compounds were proven by 2f-ray crystallography. The thermal and photochemical reactions of 1,4-dithiin sulphoxides... 

N— compounds used as acid inhibitors include heterocyclic bases, such as pyridine, quinoline and various amines. Carassiti describes the inhibitive action of decylamine and quinoline, as well as phenylthiourea and dibenzyl-sulphoxides for the protection of stainless steek in hydrochloric acid pickling. Hudson refer to coal tar base fractions for inhibition in... 

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