49833-12-7

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The enantiomers of the cyclic thiolsulfinate naphtho[1,8-cd]-1,2-dithiole 1-oxide, (±)-1, have been obtained by semipreparative chiral liquid chromatography of the racemate and characterized by chiroptical methods. The inherent dissymmetry of the extended chromophore gives rise to a very high specific rotation (> 1500 in CH2Cl2 at 546 nm). The enantiomers of the corresponding sulfoxide, 2H-naphtho[1,8-bc]thiophene 1-oxide (±)-2, showed the chiroptical behaviour expected for an aryl alkyl sulfoxide. CD spectra of 1 and 2 were completely different and could not be used to determine their relative configuration, showing the large effect from substituting S for CH2 on the electronic transitions in the system. The racemization of (+)-1 was studied at 80°C and the rate was found to be increasing rapidly with increasing polarity of the solvent, being 55 times higher in water than in 1-propanol.

Unlike open chain disulfides or even cyclic disulfides, which are readily oxidized by N2O4 and aqueous bromine to sulfinyl and/or sulfonyl derivatives, 1,2-dithiaacenaphthene is readily nitrated with N2O4 and brominated with aqueous bromine at the naphthalene ring.Other oxidants, such as Fenton system: H2O2-TiCl3, gave predominantly 1,2-dithiaacenaphthene 1-oxide as in the oxidation with H2O2.

The behavior of cyclic thiolsulfinates 5 and 6 (dibenzo-1,2-dithiin 1-oxide and naphtho-1,2-dithiole 1-oxide> upon treatment with either sulfite, cyanide, or t-BuS(1-) ions has been examined and compared with the behavior of the corresponding thiolsulfonates 1 and 2 (dibenzo-1,2-dithiin and naphtho-1,2-dithiole 1,1-dioxides).Very marked differences are observed.Whereas thiolsulfonates 1 and 2 are converted essentially quantitatively to ring-open substitution products (3 and 4) upon treatment with excess sulfite, cyanide, or t-BuS(1-), with thiolsulfinates 5 and 6 the equilibrium constants for opening of the sulfur-containing ring are so much smaller that only in the case of 5 and t-BuS(1-) is the equilibrium constant large enough that a significant fraction of the thiolsulfinate is converted to ring-opened product (7 or 8) at equilibrium.Kinetic studies of the rates of nucleophile-catalyzed racemization of optically active 5 and 6 show that the major factor responsible for the dramatic difference in the magnitude of the equilibrium constants is not a decrease in the rate constant for opening of the ring by the nucleophile but rather a huge increase in the rate constant for the reverse of the ring-opening reaction, which in the case of the thiolsulfinates involves displacement of the nucleophile from SNu by a sulfenate group, whereas for the thiolsulfonates it is a sulfinate group that performs the same displacement.In the 5-t-BuS(1-) system the rate constant for the displacement by the sulfenate is 30000 times faster than the rate constant for the corresponding displacement in the 1-t-BuS(1-) system involving the sulfinate; this provides thefirst quantitative measure of just how much more reactive a sulfenate ion is as a nucleophile than the corresponding sulfinate.Other aspects of the kinetics of the reactions of 5 and 6 with these nucleophiles provide additional information on the behavior of 7 and 8 and their conjugate acids and thereby furnish new insight into the chemistry and reactivity and of arenesulfenates and arenesulfenic acids.