Hydromagnesite Rectangular Thin Sheets as Efficient Heterogeneous Catalysts for the Synthesis of 3‑Substituted Indoles via Yonemitsu-Type Condensation in Water

The anisotropic controlled assembly of nanobuilding blocks into uncommon uniform rectangular thin sheet morphology of hydromagnesite (RS-HM) with a high surface area of 110 m²/g was achieved by a simple conventional heating under green reaction condition. The synthesized RS-HM was calcined at 450 °C in the presence of air and resulted in the formation of MgO with a surface area 120 m²/g. RS-HM was found to be a more efficient catalyst than MgO for the synthesis of novel 3-substituted indoles via Yonemitsu-type condensation selectively in excellent yields. The present method has advantages such as environmentally benign, ease to handle, selectivity and excellent yields, low <i>E</i>-factor (0.15) and high atom economy (96%)