Norbornene, selective hydrogenation

Since this reaction is a unimolecular example of the selective hydrogenation of an alkene mixture, the successful saturation of the less-substituted double bond should take place most readily over those catalysts that are most effective for the preferential saturation of one olefin in a mixture. Ruthenium has not been used extensively for such hydrogenations, but P-2 Ni(B) has been effective in promoting the selective hydrogenation of one of the double bonds in 46, methylene norbornene (49) (Eqn. 15.30), dicyclopentadiene (50) (Eqn. 15.31), and 2-methyl-1,5-hexadiene (51) (Eqn. 15.32).6 9,80,81... 

P-2 Nickel boride shows a remarkable ability to selectively hydrogenate the strained double bond of norbornene. Thus hydrogenation of 5-methylenenor-bornene (1) and of the endo-dicyclopentadiene (3) give essentially quantitative yields of the dihydro derivatives (2) and (4), respectively.8... 

Nickel affords selective catalysts for the hydrogenation of alkenes, dienes, and alkynes. When catalyzed by C. A. Brown s P-2 nickel, prepared by the reduction of Ni(0Ac)2 with NaBH in ethanol, the individual rates as well as the competitive rates appear to be sensitive to the alkene structure as judged by the reported initial rates of hydrogen addition (ref. 23). Alkene isomerization is relatively slow. Except for the most reactive alkenes such as norbornene, the individual hydrogenations seem to be first order in alkene. This indicates that alkenes are more weakly bound to Ni than to Pt or Pd. Similar selectivities are reported by Brunet, Gallois, and Caubere for a catalyst prepared by the reduction of Ni(0Ac)2 with NaH and t-amyl alcohol in THF (ref. 27). 

In this study we show that it is possible to selectively epoxidize higher olefins to their corresponding epoxides if the olefins do not contain reactive allylic hydrogen atoms. Many olefins, including styrene, substituted butadienes, and norbornene have been selectively epoxidized. Because of the usefulness of 3,4-epoxy-1-butene as a new chemical intermediate, most of the data and discussion will involve the selective epoxidation of butadiene. The catalyst composition and overall kinetics of the reaction will be discussed in some detail. 

IrHj (diene) (PPhg )2 either by H2 elimination or by hydrogenation of coordinated nbd to norbornene. Further examples of hydroxy-directed stereochemical control occur in cyclic and acyclic systems catalysed by [Ir(cod) (py) (PCyg )] PFg and [Rh(nbd) (dppb)]BF, unless steric conjestion overrides . However, 3-methylene cyclohexanol gives trans-3-methvlcvclohexanol with 98% selectivity but low selectivity is observed for 2-methylenecyclohexanol . ... 

---