Reduction reactions Chlorodiisopinocampheylborane

Oxidation reactions r-Butyl hydroperoxide-Dialkyl tar-trate-Titanium(IV) isopropoxide, 51 m-Chloroperbenzoic acid, 76 Reduction reactions Chlorodiisopinocampheylborane, 72 Diisobutylaluminum hydride-Tin(II) chloride- (S) -1 - [ l-Methyl-2-pyrrolidi-nyljmethylpiperidine, 116 Lithium borohydride, 92 Lithium tri-sec-butylborohydride, 21 B-3-Pinanyl-9-borabicyclo[3.3.1]-nonane, 249... 

Asymmetric reduction of the ketone on a 1.0-g (4.0-mmol) scale to provide (R)-(-)-2,2-diphenylcyclopentanol (96% ee) has been reported employing (+)-( -chlorodiisopinocampheylborane however, the reaction is extremely slow and inefficient [70% yield, 5 days, 2.6 equiv of (+)-p-chlorodiisopinocampheylborane].5 Other efforts to obtain enantiomerically pure 1 by means of enzymatic hydrolysis of the corresponding racemic acetates using horse liver acetone powder (HLAP) and pig... 

The oxazaborolidine-catalyzed borane reduction to prepare (R)-1 is an improvement over existing methods such as the p-chlorodiisopinocampheylborane reduction,6 and enzymatic resolution14 for several reasons. First, the reaction uses an easily obtained catalytic reducing agent that provides the chiral alcohol in 92% ee. Secondly, the reaction proceeds at a reasonable rate (6-8 hr) and affords the chiral alcohol (92% ee) In nearly quantitative yield (97%). Finally, the work-up, isolation and purification of the product is straightforward and requires no column chromatography, only bulb-to-bulb distillation and recrystallization, affording (R)-1 in 75% yield with 97% ee. In addition, the catalyst precursor, (S)-a,a-diphenylpyrrolidinemethanol. can be easily recovered in excellent yield. 

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