Enantioselective hydroboration of cyclopentadiene Ipc-borane

^{Click the reaction arrow in sequence to view the 3D models and animations respectively}

Diisopinocampheylborane (Ipc)₂BH (from pinene) is an enantioselective hydroboration reagent. In the case of a substituted cyclopentadiene, attack occurs opposite the methyl group to establish two stereogenic centres. The two terpene fragments dictate the enantioselectivity. The methyl group can only accommodate a hydrogen from the alkene in the transition state.

The product borane is converted to the alcohol with retention of stereochemistry by the H₂O₂/NaOH mechanism.

H. C. Brown and P. Veeraraghavan Ramachandran, J. Organomet. Chem., 1995, 500, 1–19.