Behaviour of Arylazo tert-Butyl Sulfides with Ketone Enolates. Competition between SRN1 α-Arylation and Azocoupling Reactions.

Article abstract of DOI:10.1016/S0040-4020(01)88144-8

(Z)-Arylazo tert-butyl sulfides 1a-i react, in DMSO and at room temperature, with potassium acetone enolate to give good yields of 1-aryl-2-propanones via spontaneous S_RN1 dark reactions. α-Phenylation of pincolone and acetophenone enolates by 1a likewise occurs in excellent yields.In agreement with the involvement of an electron-transfer catalyzed chain process, the reaction of the 4-bromo derivative 1n with pinacolone enolate gives mainly the bis-substitution product 13.With azosulfides 1j-m the arylation pathway competes with a base-induced thiol elimination eventually leading, depending on the structure of the azosulfide, to indazoles 8 or 11 and/or to 2-oxopropanal arylhydrazones 9, 10 or 12.