General procedure for the synthesis of 2-chloro-5-ethylpyridine from 2-chloro-5-vinylpyridine: 2-chloro-5-vinylpyridine (1 g, 7.2 mmol) was dissolved in 20 mL of methanol. Hydrogen was passed into the resulting solution for 2 min, followed by the addition of 1,5-cyclooctadiene(pyridine)(tricyclohexylphosphine)iridium(I) hexafluorophosphate catalyst (0.1 g). The mixture was placed in a hydrogenation reactor and reacted for 2 hours under 1 atm hydrogen. Upon completion of the reaction, the reaction solution was filtered through diatomaceous earth and concentrated. The organic phase was separated by adding 10 mL of dichloromethane and 10 mL of water to the concentrate. The organic phase was dried with anhydrous magnesium sulfate, filtered and the solvent was evaporated and concentrated to give 0.84 g of 2-chloro-5-ethylpyridine as a pale yellow liquid in 83% yield.
