Lindlar catalyst

A Lindlar catalyst is a heterogeneous catalyst consisting of palladium deposited on calcium carbonate or barium sulfate then poisoned with various forms of lead or sulfur.

Lindlar catalyst is commercially available but can also be created by reducing palladium chloride in a slurry of calcium carbonate (CaCO3) and adding lead acetate.

[1][2] A variety of other "catalyst poisons" have been used, including lead oxide and quinoline.

Alkyne hydrogenation is stereospecific, occurring via syn addition to give the cis-alkene.

An example of commercial use is the organic synthesis of vitamin A which involves an alkyne reduction with the Lindlar catalyst.