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. Author manuscript; available in PMC: 2009 Jun 23.
Published in final edited form as: J Org Chem. 2008 May 1;73(11):4017–4026. doi: 10.1021/jo800204n

Table 3.

Optimization Studies for the Asymmetric Reduction of Pyridyl Ethanone O-Benzyl Oximes

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entry benzyl oxime cat 10 (equiv) T (°C) solvent time (h) yield (%)a ee (%)b
1 16a 0.1 0 THF 72 46 92
2 16a 0.1 25 THF 48 53 89
3 16a 0.1 0 t-BuOMe 72 42 93
4 16a 0.1 0 dioxane 72 38 98
5 16a 0.3 0 dioxane 72 50 99
6 16a 0.3 10 dioxane 48 75 98
7 18a 0.1 0 THF 72 38 99
8 18a 0.2 10 dioxane 72 64 94
9 18a 0.1 25 THF 48 63 90
10 18a 0.3 10 dioxane 48 84 99
11 18a 0.5 10 dioxane 48 79 98
a

The reactions were carried out using 5 equiv of borane stabilized with NaBH4. Isolated yield of amides by column chromatography.

b

Determined by GC of acetyl derivatives on a chiral column (CP-Chirasil-Dex-CB).