C-S bond breaking

Thiazolidines undergo hydrolysis to aldehyde and amino thiol under acid or basic aqueous conditions. The reaction involves C—S bond breaking and proceeds by the formation of an iminium thiolate zwitterion intermediate (460) (91JA3071). 

Electron-rich metal fragments can react with 2-substituted In yielding either the kinetic C-H or the thermodynamic N-H insertion products. C-N bond activation, on the other hand, is not observed, in contrast with C-S bond breaking, which is readily promoted by electron-rich metal centers, as described in Chapter 4. 

Desulfurization of polynuclear thiophenes was performed by continuous stirring with a Raney nickel catalyst in ethanol at 0-78.8 °C. The major products were biphenyl in the desulfurization of dibenzothiophene, a-phenylnaphthalene in the desulfurization of benzo[b]naphtho[l,2-d]thiophene, and -phenylnaphthalene in the desulfurization of benzo[b]naphtho[2,3-d]thiophene and benzo[b]naphtho[2,l-d]thiophene. Observation of these products shows that the main reaction pathway is the extrusion of a sulfur atom to give the corresponding hydrocarbon. The tt-electron densities of the sulfur atoms, which were calculated by using simple Huckel molecular orbital theory, are considered to be related to the adsorption of the sulfur compounds to the surface and consequently to the C-S bond-breaking rate. 

In this respect, attention should be drawn to an outstanding study of Koganl on the catalyst structure and mechanism of C-S bond breaking, studied by isotopes, applying the results obtained by other developed methods. 

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