Electrochemical intramolecular cyclisation of propargyl bromoethers catalysed by nickel complexes

The electrochemical intramolecular cyclisation of propargyl 2-bromoethers 1 - 3 in N, N'-dimethylformamide at constant current in a diaphragmless cell has been developed using Ni-II complexes as electron-transfer mediators. During controlled-current electrolyses of solutions of Ni-II complexes in the presence of bromoethers, catalytic reduction of the latter proceeds via one-electron cleavage of the carbon - bromine bond to form a radical intermediate that undergoes cyclisation to afford the cyclic compounds in moderate to good yields.