Evidence for intermolecular interaction between sulfonium and sulfide sulfur atoms and its application to synthesis of cyclic bis(disulfide) dimer

On the basis of the remote Pummerer reaction of p-bis(alkylthio)-aromatic S -oxides, the intermolecular interaction between the sulfonium and sulfide s ulfur atoms is described. (1) In marked contrast to the Pummerer reaction o f 1b-d(3) with (CF3CO)(2)O (J. Org, Chem. 1999, 64, 3190-3195), the reactio n of 3,3 ' ,5,5 ' -tetramesityl-4-(trideuteriomethylsulfinyl)-4 '-(methylth io)biphenyl (1a-d(3)) as a sterically hindered analogue of Ib gave only 2a- d(2). (2) Both reactions of the two unsymmetrical regioisomers of 1-(ethylt hio)-4-(methylthio)benzene S-oxide (5a and 5b) with (CF3CO)(2)O afforded a mixture of the mono-Pummerer products 6a and 6b, the bis-Pummerer product 7 , and the bissulfide 8 in a similar ratio. The quenching at the initial sta ge of both reactions produced 5a, 5b, 8, and the bis-sulfoxide 10 in a simi lar ratio. These results indicate the equilibrium the intermolecular intera ction between the sulfur atoms. (3) The reaction of the p-bis(benzylthio)ar omatic S-oxide 16 with (CF3SO2)(2)O gave the cyclic bis(disulfide) dimer 17 for the diphenyl sulfide and diphenylmethane spacers or the cyclic tetraki s(disulfide) tetramer 19 for the benzene and biphenyl spacers via the deben zylation of an intermolecular dithia dication. The cyclic bis(dithia dicati on) dimer A resulting from the intermolecular interaction between the sulfo nium and sulfide sulfur atoms is proposed as an intermediate throughput the present reactions.