[3 + 2] cycloaddition of 1-(4-Methoxybenzyl)indoles and azaindoles with nitrile oxides

We studied [3 + 2] cycloaddition reactions of indoles and azaindoles with various nitrile oxides. N-Protection of indoles and azaindoles with the 4-methoxybenzyl group was found to be effective for [3 + 2] cycloaddition with nitrile oxides. Due to the propensity of the nitrile oxides to dimerize, it was necessary to optimize reaction conditions in the case of unstable nitrile oxides. This method was used to synthesize various key intermediates of biologically active 3-substituted azaindole derivatives.