A Facile Method for the Synthesis of 3-Alkyloxindole

Benzylamine in combination with acetic acid was identified as a powerful catalyst for the condensation of oxindole with aldehydes, acetone or cyclic ketones. A variety of 3-alkyloxindoles could be readily prepared in 10 mmol scale via the sequential benzylamine acetate catalyzed condensation of oxindoles with aldehydes (or ketones) and conjugate reduction by NaBH4. Keywords: 3-alkenyloxindoles, 3-alkyloxindoles, benzylamine, conjugate reduction, carbonyl compounds, Knoevenagel condensations, alkylation, oxindoles, amination, arylation