Reductive cyclisation of propargyloxy and allyloxy α-bromoester derivatives using environmentally friendly electrochemical methodologies

The electrochemical intramolecular cyclisation of alpha -bromo propargyloxy (1 and 2) and allyloxy (3) esters was carried out in ethanol and in ethanol-water mixtures as environmentally friendly systems using Ni(II) complexes as the catalysts. The reduction of the substrates proceeds one-electron cleavage of the carbon-bromine bond to form a radical-type intermediate that undergoes cyclisation to afford cyclic ethers in moderate to good yields.