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Z-selective reduction of alkynes using Lindlar’s catalyst

المؤلف:  Jonathan Clayden , Nick Greeves , Stuart Warren

المصدر:  ORGANIC CHEMISTRY

الجزء والصفحة:  ص681-682

2025-07-06

1005

The Z alkene below was needed pure for studies on the mechanism of a rearrangement reaction, you met catalytic hydrogenation as a means of reducing alkenes to alkanes, and we introduced Lindlar’s catalyst (palladium and lead acetate on a support of calcium carbonate) as a means of controlling chemoselectivity so that alkynes could be reduced to alkenes. What we did not emphasize then was that the two hydrogen atoms add to the alkyne in a syn fashion and the alkene produced is a Z alkene. The stereoselectivity arises because two hydrogen atoms, bound to the catalyst, are delivered simultaneously to the alkyne.

The compound below is the pheromone of a destructive beetle. The synthetic pheromone can be used to trap the beetles, but it is active only as the Z isomer. Reduction of the alkyne with the Lindlar catalyst gives pure Z isomer, while the alternative way of making Z alkenes, the Wittig reaction, gives significant amounts of the E isomer.