Indirect electrochemical cyclization of bromoalkoxylated derivatives mediated by nickel(II) complex in environmental-friendly medium

An improved procedure has been developed using a catalytic amount of a nickel(II) complex in the efficient and selective electrochemical cyclization of propargyloxy and allyloxy bromo derivatives into substituted tetrahydrofurans using ethanol and ethanol–water mixtures as environmental-friendly systems. The reduction of the substrates proceeded via one-electron cleavage of the carbon–bromine bond to form a radical-type intermediate that undergoes cyclization to afford the tetrahydrofuran structures in good yields.

Graphical abstractNi(II)-catalyzed radical-type cyclization of unsaturated bromoethers to the corresponding cyclic compounds in EtOH and EtOH–H2O mixtures. Figure optionsDownload full-size imageDownload as PowerPoint slide