Novel polysulphur bridged metacyclophanes from the iron-catalysed reaction of bis-(2,4-dimethoxyphenyl) sulphide with disulphur dichloride. Evidence for the cleavage of the carbon–sulphur bond by electrophilic agents

Abstract

The iron-catalysed reaction of bis-(2,4-dimethoxyphenyl) sulphide (3) with disulphur dichloride (S₂Cl₂) in dilute chloroform solution has been investigated. Surprisingly, the reaction gives 4,6,11,13,18,20-hexamethoxy-1,2,9,16-tetrathia[2.1.1]metacyclophane (4) as the major product, accompanied by minor amounts of 3,5,10,12,17,19,24,26-octamethoxy-1,8,15,22-tetrathia[1.1.1.1]metacyclophane (5), 4,6,11,13,18,20,25,27-octamethoxy-1,2,9,16,23-pentathia[2.1.1.1]metacyclophane (6), and 5,7,14,16-tetramethoxy-1,2,3,10,11,12-hexathia[3.3]metacyclophane (1). The ¹H n.m.r. and mass spectra of compounds (4)–(6) are briefly discussed. The unexpected formation of compounds (1) and (4) suggests the occurrence of an unusual cleavage of carbon–sulphur bonds, operated by electrophilic species on sulphur-bridged oligomers, and subsequent rearrangement of the involved intermediates to the cyclic derivatives. This interpretation is supported by the successful chlorinolysis under mild conditions of the sulphide (3) by means of sulphuryl chloride, affording 1,3-dichloro-4,6-dimethoxybenzene (8) and bis-(5-chloro-2,4-dimethoxyphenyl) disulphide (9). A probable reaction pathway is proposed.