Comparative study of “ship-in-a-bottle” and anchored heterogenized Rh complexes

Heterogenized rhodium complexes were prepared by two different methods (“ship-in-a-bottle” and anchoring methods) and the catalysts were used in the hydrogenation of simple and prochiral alkenes. The “ship-in-a-bottle” type heterogenized rhodium complexes were active in the hydrogenation of hex-1-ene, cyclohexene, and 1-methylcyclohexene. At the same time the heterogenized catalyst had all the expected advantages of the heterogeneous system, namely easy handling and recyclability. The anchored catalyst could also catalyze the same hydrogenation reactions and showed all the advantages of the heterogeneous catalysts. However, the latter one was much more active in the above hydrogenation reactions than the “ship-in-a-bottle” type catalysts. Moreover, the anchored catalyst showed higher ee in the enantioselective hydrogenation of trans-2-methylpent-2-enoic acid than its encapsulated counterpart.