Deoxydesulfurization of sulfones derived from dibenzothiophene using nickel compounds

Catalytic amounts (1 mol%) of [Ni(dippe)H]2 (1), [Ni(dcype)H]2 (2), [Ni(dtbpe)H]2 (3), NiCl2·6H2O (4) and [Ni(dippe)(Me)2] (5) reacted with MeMgBr to yield the straightforward deoxydesulfurization of sulfones of dibenzothiophene (DBTO2), 4-methyl-dibenzothiophene (MeDBTO2) and 4,6-dimethyl-dibenzothiophene (Me2DBTO2), thereof producing the corresponding sulfur-free biphenyls (85–100% yield) when using a solvent mixture of toluene–THF, 10:2 v/v. The formation of key intermediates of the type [(dippe)Ni(κ2-(O,O)(sulfone)] play an important role in the activation of the C–S bond in the sulfone as they participate in the ultimate deoxygenation step, even with the more hindered substrates. The formation of MgO and MgS from the catalytic process is envisioned as the driving force for the whole reaction.

The use of catalytic amounts of compounds of the type [Ni(diphosphine)H]2 allowed the deoxydesulfurization of dibenzothiophene-sulfones, quantitatively yielding biphenyls.Figure optionsDownload as PowerPoint slide