In this paper, an alternative and efficient copper(I)-catalyzed synthesis of 2-sulfonyliminocoumarins is developed through a three-component reaction of ortho-hydroxybenzyl alcohol, alkynes, and p-toluenesulfonyl azide. The proposed route for access to the 2-iminocoumarin ring involves a [4 + 2] hetero-Diels-Alder reaction between ortho-quinone methide and ketenimine intermediates generated in situ.
Keywords: alkyne; copper-catalyzed; ortho-hydroxybenzyl alcohol; sulfonyliminocoumarins.