Hydrovinylation of norbornene. Ligand-dependent selectivity and asymmetric variations.

[reaction: see text] Norbornene undergoes Ni-catalyzed (1-2 mol% allylnickel bromide/phosphine/NaBARF or AgSbF(6), 1 bar ethylene, -50 degrees C) hydrovinylation (>97% yield), giving either a 1:1 or a 2:1 (norbornene/ethylene) adduct depending on the size of the phosphine. Use of binaphthol-derived phosphoramidite ligand results in up to 80% ee for the 1:1 adduct. The course of the reaction is highly dependent on the ligand (size and configuration of the appendages) and the counteranion present.