Zinc bromide supported on hydroxyapatite as a new and efficient solid catalyst for Michael addition of indoles to electron-deficient olefins

The synthesis of 3-substituted indoles was carried out in presence of zinc bromide supported on hydroxyapatite. The substitution on the indole nucleus occurred exclusively at the 3-position and N-alkylation products have not been observed. The results obtained in this reaction demonstrate the potential application of hydroxyapatite as inorganic macroligand for Lewis acid catalyst.