Enantioselective Reduction of Ketones with BINAL-H

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Asymmetric reduction of carbonyl with BINAL-H

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The unsaturated group (alkyne in this case) has an unfavourable orbital interaction with lone pairs on the BINOL oxygen, so it is equatorial. This gives only one face for the hydride to attack. Note the transition state is a distorted chair - this is due to the number of heteroatoms (atoms other than carbon) in the ring.

Animations based on R. Noyori, I. Tomino, Y. Tanimoto and M. Nishizawa, J. Am. Chem. Soc. 1984, 106, 6709-6716