BEHAVIOR OF ARYLAZO TERT-BUTYL SULFIDES WITH KETONE ENOLATES - COMPETITION BETWEEN SRN1 ALPHA-ARYLATION AND AZOCOUPLING REACTIONS

(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(RN)1 dark reactions. Alpha-Phenylation of pinacolone 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.