Al-MCM-41 as a mild and ecofriendly catalyst for Michael addition of indole to α,β-unsaturated ketones

Mesoporous Al-MCM-41 catalyzes the chemoselective Michael addition reaction between indoles and α,β-unsaturated ketones to afford β-indolylketones at room temperature with excellent yields. The higher catalytic activity is attributed to Lewis acidic Al and the large surface area. The catalyst is readily recovered and reused more than six times without loss in its catalytic activity. The substitution at the indole nucleus occurs exclusively at the 3-position and N-alkylation products are not observed.

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► Al-MCM-41 catalyzes the chemoselective Michael addition reaction between indoles and α,β-unsaturated ketones.
► This procedure is operationally simple and can furnish a wide variety of 3-substituted indole derivatives.
► This method is a practical alternative due to its simplicity, environmental acceptability and inexpensiveness.
► The catalyst is readily recovered and reused more than six times without loss in its catalytic activity.