CYCLIZATIONS .3. USE OF A MILD-STEEL CATHODE IN THE ELECTROCHEMICAL INTRAMOLECULAR CYCLIZATION OF ARYL HALIDES

One electron reduction of aryl halides is known to generate the aryl r adical and halide ion. These aryl radicals will cyclize onto an adjace nt benzene ring in a reaction that is potentially useful in organic sy nthesis and which is well documented at a mercury cathode. 5-(2-Haloph enyl)-1-(4-fluorophenyl)tetrazoles are used here as representative sub strates and the cyclization reaction to 7-fluorotetrazolo[1,5-f] phena nthridine is developed at cathodes of cadmium, zinc and mild-steel. A high yield of the desired cyclization product is achieved using a mild -steel cathode and a sacrificial magnesium anode in an undivided cell with acetonitrile, 0.1 M tetraethyl ammonium tetrafluoroborate as elec trolyte and under an air atmosphere.