Enantioselective hydroboration of cyclopentadiene Ipc-borane
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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.