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Please login or sign up for a free trial to access the full content. 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, 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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M eeeeeeee eeeeeee ee eeeeee(eeeeeeeeeeeeeeeee)eeeeee (88) ee eeee ee eeeeeeee eeeeeeeeeee eeeeeeeeee eeeeeeeeeeeee, eeeeeee eee eeee-eeeeeeeeeeee (eeee-88) ee eeeeeeeeeeeeeeeee eeee eeeeee eee eeee eeeeeee eeeeee eeeeee eeeeeeeeeeeee eeee eee M,M- ee M,M-eeeeeeeeeeeee, eee ee e eeee eeeeee eeeeeeee eeeee.[‌88‌] Me e eeeeee, ee eee eeeeee eeeeeeee ee eeeee eeee eeeeeeeeeee 88% ee ()-α-eeeeee [()-88/(+)-88, 88:88] eee e eeeeee ee eeeeeeeeeeeeee ee eeeeeee eeeeeeee eeeee (+)-eeeeee(eeeeeeeeeeeeeeeee)eeeeee (eee-88) eeee eeeeeee ee eeee eeeee eeeeee 888 ee eee eeeeeeeeeeeee M-eeeeeee 888 ee 88% ee (Meeeee 88). Mee eeeeeee ee ee eeeeeeeeeeee ee eee eeeeeeeee ee M-888,888, e eeeeeeeeeee eeeeeeeeee.[‌88‌] Mee eeee eeeeeeeeeeee eeeeee eeeeeee eeee eee eeeeeee ee ()-eeeeee(eeeeeeeeeeeeeeeee)eeeeee [()88] ee eee eeeeeee ee eeeee 8.8% ee eee eeeeee ee (+)-88 ee eee eeeeeee.

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Meeeeeeeeeeee ee e eeeeeee eeeeeee ee α-eeeeeee eeeeee e eeeeeee eeee ee 88% eeee-88 eee 88% eeee ee eee eeeeee eeeeeee.[‌888‌] Meeeeeeeeeee eeeeeeee ee eee eeeeeee eeeeee eeeeee eee eeeeeeeeeeeee eeeeeee eeeeee eeee eee eeeeeeee eeeeee eeeeee eeee eee eeeeeeeeeeeee ee eeeeeeeee eeeee, eee eee eeeeee ee eeeeeeeeeee ee eeeeeeeeeeeee ee eee eeeeee eeeee eeeeeeee eee eeeee.

Meeeeeeeee eeee ()-88 eeee eeeeeee eeeeee eeeeeee eeeeeeeeeee.[‌888‌] M eeeeeee eeeeeee ee eee eeeeeeeeee ee eee eeeeeee eeeeeee ee (M)- eee (M)-8-eeeeeeeeeeeeeee-8-eeeeeeeeeeeeeeeeeeeee (M)- eee (M)-888 eeee e eeeeeee ee eeeeeeeee (M)-888 eee (M,M)-8-eeeeeeeeeeeeeee-8-eeeeeeeeeeeeeeeeeee [(M,M)-888] (88% ee) eeeeeee eeee (M)-888, eeee e eeeee eeeeee ee (M,M)-888 (88% ee) eeee (M)-888 (Meeeee 88). Mee eeeeeeeeeeee eeeeee ee eee eeeeeeeee (M)-888 eee ee eeee eeeeeeeeeee eeee ee eee eee ee eeee eeee 8.8 eeeeeeeeeee ee ()-88 ee eee eeee ee eeeee eeeeeeee, eeeeeeee eeee eeeeeeeeee ee eeee eeeeeeeeeeee (M,M)-888. Mee eeeeeeee eee eeeeeeeee ee eeeeeeeeeeeeee. Mee eeeeeee eeeeeeeeee ee eeeeeee eeeeeeeeeee eeeeeee[8.8.8]eeeeeeee eee eeee eeeeeeee.[‌888‌] Meeeeeeeeeeeeeeeee ee eee eeeeeeeee ee eeeeee eeeeeeeeeee eee eeee eeee eeee eee eeeeee(eeeeeeeeeeeeeeeee)eeeeee eee eeeeee eeeeeeeeeee eeee e eeee eeeeeee ee eeeee eeeeeee, eee eeee eeeee eee eeeee eeeeeee-eeeeeeeeee eeeeeeeeeeeeeeeeee eeee eee eeeeee eeeeeeee eeeeeeeeee eeee.[‌888‌]

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Meeeeeee 888 ee Meeeeeeeee Meeeeeeee ee Meeeeeee Meeeeeeee eeee ()-Meeeee(eeeeeeeeeeeeeeeee)eeeeee [()-88]; Meeeeee Meeeeeeee.[‌88‌]

()-Meeeee(eeeeeeeeeeeeeeeee)eeeeee (88) (8.8e, 88eeee) eee eeeeeeeeeee ee e eeeee eee eeee e 88-eM, eeeee-eeeeeeee eeeee eeee eee eeee eeeee ee ee eeee eee eeeeee eeeee M8 eee eee eeeeeeee eeee e eeeeeeee eeeeeeee eee, eeee-eee eeeeee eeee e eeeeee, eee e eeeeeeeeee eeee. Mee eeeeeeeeee ee eeee eeeee eeeeeee, MMM (88eM) eee eeeee eee eee eeee eee eeeeee ee 88°M eeeeee eeeeee eee eeeeee (88eeee); e eeeeeeeeeee ee 88°M eee eeeeeeeeee eee eee eeeeeeee ee eee eeeeeeee. Mee eeeeeeeeee eeeeeeee eeeee eeee-eeeee eeeeeee, eee eeeeeee eee eeeeeee eee eee eeeeeeee eee eee ee ee. Me eeeeeee eee eeeeeeee, eeeeeeee eeee eeeee ee eeeeeeee eeeeeeeee, eeeeeee eeee eeee MeMM (88°M), eee eeeeeeee ee 88MMMM. Meeee eee eeeeeeee eee eeeeeeee, eee MMM eee eeeeeeeee ee ee eeeee eeeeeeeee eeeeee eee eee α-eeeeee eeee eee eeee eeeeeeeee eeeeee eee eeeeeeee eee eeeeeeeee ee eeeeeeeeeeee eeee e eeee eeee eeeee eeeeee (8.8Meee, 8e). Mee eeeeeee ee eeeeee(eeeeeeeeeeeeeee)eeeeeeee eeeee eee eeeeeeeee ee Me8M (888eM) eee eeeeeee eeee eeeeeeeeeeeeee (88eeee). Meeee eeeeeeee eee 8e, eee eeeee eeeeeeeeeeeeee eeeee 888 ee eeeeeeeeeeeeeeeeeeeeee eeee eee eeeeeee ee eeeeeeeeee eee eeeeee eeee eeeeeee (8×88eM). Mee eeeeeeee eeeeeeeee eeee eeeeeeeeeeee eee eee eeeeeee ee eeeeeeeee eeeeeee eee eeeeeeeee (eeeeee eeeeeee >88%). Meeeeee eeeeeeeeeeee eee eeeeeeeeeeee ee eeeeeeeeeee MM (MM-8888 ee Meeeeeee 88M eeeeee). Meeeeeeeee ee ee eee eeeeeee eee ee eeeeeee eeeeeeee eeeeeeeeeee eee ee eeeeeeeeee ee ee α-eeeeeee-eeeeee-α-eeeeeeeeeeeeeeeeeeeeee (MMMM) eeeee ee eee eeeeeee ee eee eeeeeeeeeeeeeeeeeee (MMM) eeeeeeeee eeeeeeee ee eeeeeeeee MM eeeeeeee.

Meeeee 8-(8M)-8-{8-[(M)-8-(8-Meeeeeeeeeeeee-8-ee)eeeee]eeeeee}-8-eeeeeeeeeeeee)eeeeeeee (888) Meeee Meeee (+)-Meeeee(eeeeeeeeeeeeeeeee)eeeeee [(+)-88]:[‌88‌]

(+)-Meeeee(eeeeeeeeeeeeeeeee)eeeeee [(+)-88] eee eeeeeeee eeee ()-α-eeeeee (88% ee, 8.88M, 88.88eee) eee MMMe8MMM ee eeeeeeeee ee Meeeeee Mee eeee ee eeeee 88 eee eeeee eeeeee ee e eeeeeee eeee ee eeeeee 888 (8.888ee, 8.88eee) eee eMe8MMe (888eM, 8.88eee) ee MMM (88M) ee 88 ee 88°M. Mee eeeeeee eee eeee ee 88°M eee 8.8e eee eeeeee ee 8°M eeee 8e. Meeeee MMMM eeeeeeee eee eeeeeee 888 eee eeeeeee eee eeee e Meeeeeeee MM 8.8-ee×88-ee eeeeee (eeeeeee/eMeMM 8:8, 8.8eM·eee8, eeeeeeeee ee 888ee; eee eeeee 888, 88.8eee; (M)-eeeeeee eeeee 888, 88.8eee; (M)-eeeeeee eeeee eee-888, 88.8eee). Meee eee eeeeeeee eee eeeeeeee, ee eee eeeeeeee eeee eeeeeee (888eM) eee eee eeee eee eeeeeee ee ee eee 88e. M 88% ee eeee ee eeeeeeeee eeeeee eeeeeeee (88M) eee eeeee ee 88°M, eee eeeeeee eee eeeeeee eee 88eee, eee eee eeeeee eeee eeeeeeeee. Mee eeeeeee eeeee eee eeeeeee eeeeee eeee 88% eee. eeeee (88M). Mee eeeeeee eeeee eee eeeeeeeee eee eee eeeeee ee eee eeeeeee eeee eee eeeeeee eeeee eeeeee ee 88M. eMeMMe (88M) eee eeeee, eee eee eeeeee eee eeeee eeeeeee ee 88M. M8M (888eM) eee eeeee ee eee eeeeeee, eee eee eeeeee eeeeee eee eeee eee 88eee eeeeee eeeeeeee eeee eeeeeee (88M). Meeee eeeee eee eeeeeee 88eee, eee eeeeeeeeeeee eeeeeee eee eeeeeeeee ee eeeeeeeeee. Mee eeee eee eeeeee eeee eMeMMe/eeeeeee (8:8; 88M) eeeeeeee eeee eeeeeee (88M) eee eeeee. Mee eeeeeee eeeee 888 eee eeeeeeee ee eee eeeeeeeeeee; eeeee: 8.88ee (88%); 88% ee; ee 888888°M; [α]M88 88.8 (e 8, MMM88).