Cyclooctene sulphide

An illustrative example of oxirane formation by the action of alkali on a / -halohydrin is to be found in the reaction sequence involved in the Darzens glycidic ester synthesis (Section 5.7.6, p. 598). Three target molecules, namely 2-phenylaziridine (4), methyl (S)-thiiranecarboxylate (5) and cyclooctene sulphide (6), are selected here to exemplify this intramolecular cyclisation reaction type. 

A further example of this general type of reaction is provided by the synthesis of cyclooctene sulphide (6).4 Here an alkene is converted into an adduct with succinimide-A-sulphenyl chloride (reaction formulated in full in Expt 8.3), which is reduced with lithium aluminium hydride at — 78 °C to form the product. 

Cyclooctene sulphide. The foregoing imidosulphenyl chloride (6.6 g, 0.04 mol) is dissolved in dichloromethane (25 ml) to form a yellow solution which is added dropwise at room temperature to cyclooctene (4.5 g, 0.041 mol) in dichloromethane (50 ml). The mixture is stirred until no yellow colour persists. 

The foregoing adduct (9.4 g, 0.034 mol) is dry tetrahydrofuran (25 ml) is added dropwise to a stirred suspension of lithium aluminium hydride (1.1 g) in tetrahydrofuran (10 ml) at — 78 °C under nitrogen. After stirring for 10 minutes, the mixture is allowed to warm to room temperature and then quenched with water. The episulphide is extracted with ether and, after drying over magnesium sulphate, the solvent is removed and the residue distilled under reduced pressure to afford cyclooctene sulphide (4.7 g, 97.35%), b.p. 50 °C/2 mmHg. 

Diederich et al. had postulated that the highly reactive iron-oxo species, arising from oxygen transfer from the oxidant to the Fem site [87], should be greatly stabilised by enclosure within a dendritic superstructure. The catalytic potential of the dendrimers 6 a-c was determined in the epoxidation of alkenes [83 a, 88] (1-octene and cyclooctene) and the oxidation of sulphides [83 a] ((methylsulphanyl)benzene and diphenyl sulphide) to sulphoxides - in dichloro-methane with iodosylbenzene as oxidising agent. Compared to the known metal-porphyrin catalysts, 6a-c exhibit only low TON (7 and 28, respectively, for... 

Benzyl phenyl sulphide, norbornene, cw-cyclooctene, and 4-vinyl-1-cyclohexene were obtained from Aldrich and (IS)-(-)-a-pinene from Fluka. Phenyl sulphide was prepared from benzene and sulphur chloride following the literature procedure[9]. Reference samples of sulphoxides and sulphones were prepared by oxidation of sulphides with sodium periodate[10] and hydrogen peroxide[ll] respectively. Reference samples of epoxides were made by following Kaneda et al.[ 2 procedure. Metal phthalocyanines[13] were prepared from appropriate metal salt, 1,2-dicyanobenzene with ammonium molybdate as catalyst and were characterized by elemental analysis. 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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