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6.1.5.13.2 Method 2: Reduction of Ketones to Alcohols

DOI: 10.1055/sos-SD-006-00134

Matteson, D. S.Science of Synthesis, (20056233.

The synthesis of ()-chloro(diisopinocampheyl)borane (50; Scheme 21, Section 6.1.5.4.2.1), a useful reagent for the asymmetric reduction of ketones, has been described earlier.[‌95‌] The process of reducing a ketone is outlined in Scheme 67. A ketone 162 having a large (R1) and a small (R2) substituent reacts with 50 via postulated transition state 163, which is cleaved to α-pinene (49) and a chloroboronate ester of the asymmetric secondary alcohol (164). Treatment with diethanolamine then liberates the asymmetric alcohol 165 [predominantly S-isomer, assuming R1 has the higher CahnIngoldPrelog priority] and the diethanolamine ester 166 of (isopinocampheyl)boronic acid (for further examples see Table 3).

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References