Prochiral ketones which contain nitrogen atoms have been reduced enantioselectively with chiral oxazaborolidines in the presence of excess borane. However, the pyridine system has been shown to be a poor substrate for this asymmetric reduction. For example, catalytic reduction of 2-acetylpyridine with a chiral oxazaborolidine provided the product alcohol in only 28% ee. We wish to report the enantioselective reduction of 2-(bromoacetyl)-pyridine 1 with chiral oxazaborolidines. Good enantiomeric excess was obtained in the reductions (80% ee) and could be improved to ≤95% ee upon recrystallization. Subsequently, bromohydrin 6 was used to prepare Ro 25-8210.
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