Reactivity of vinyl sulphonic esters. Part XI. Behaviour of aminovinyl p-bromobenzenesulphonates

Abstract

1,2-Diaryl-2-[(N-aryl) methylamino] vinyl p-bromobenzenesulphonates, prepared by reactions of α-aryl-α-[(N-aryl) methylamino] acetophenone derivatives with p-bromobenzenesulphonyl chloride and sodium hydride, undergo two kinds of reactions. One formally involves intermediate formation of β-aminovinyl cations to give substitution products and/or cyclisation to give indole derivatives along with p-bromobenzenesulphonic acid. The other is a novel internal redox reaction which affords benzil derivatives together with p-bromobenzenesulphinic acid, and is catalysed, in inert solvents, by boron trifluoride. The cyclisation to indoles, which is catalysed by aluminium trichloride, occurs without rearrangement, indicating that a β-nitrogen atom in contrast to a β-sulphur atom, does not participate in the reaction by bridging between the two ethylenic carbon atoms.