One-pot multicomponent synthesis of highly substituted piperidines using p-toluenesulfonic acid monohydrate as catalyst

p-Toluenesulfonic acid monohydrate (p-TsOH center dot H2O) is a highly effective and efficient catalyst for the one-pot multicomponent coupling of aldehydes, amines, and beta-ketoesters in EtOH at ambient temperature to give highly functionalized piperidines in high yields. This one-pot reaction has some important advantages such as the easy workup procedure, simple and readily available precursors, nontoxic and inexpensive catalyst, and good to high yields.