Hydrogenation of functionalised pyridines with a rhodium oxide catalyst under mild conditions

Piperidines are one of the most widely used building blocks in the synthesis of pharmaceutical and agrochemical compounds. The hydrogenation of pyridines is a convenient method to synthesise such compounds as it only requires reactant, catalyst, and a hydrogen source. However, this reaction still remains difficult for the reduction of functionalised and multi-substituted pyridines. Here we report the use of a stable, commercially available rhodium compound, Rh 2 O 3 , for the reduction of various unprotected pyridines. The reaction only requires mild conditions, and the substrate scope is broad, making it practically useful. The commercially available, easy-to-handle Rh 2 O 3 catalyses the hydrogenation of functionalised pyridines under mild conditions.