Efficient synthesis of indoles from 2-alkynylaniline derivatives in water using a recyclable copper catalyst system

A recyclable, effective CuI/PSP (polystyrene-supported pyrrole-2-carbohydrazide) catalyst system was established, with which a variety of N-(2-ethynylphenyl)-sulfonamides, even those with bulky substituents on the aromatic ring, have been smoothly cyclized to indoles in water with excellent yields.