一般而言，金属氢化物还原酮为亚甲基该主要用于芳基酮或二芳基酮的还原。常见的还原剂主要为LAH和硼氢化钠，通常要和Lewis 酸联用。这类还原易于进行时，如芳环上带有许多富电子基团或二芳基的酮，有时不需要加任何Lewis 酸也可以进行。

反应实例

A solution of AlCl3 (106.7 g, 0.8 mol) in diethyl ether (200 mL) was added slowly to a stirred slurry of LiAlH4 (15.2 g, 0.4 mol) in ether (100 mL), and the mixture was stirred for 5 min. A solution of 4-methylbenzophenone (49.1 g, 0.25 mol) was then added dropwise, while the reaction mixture was stirred. The exothermic reaction kept the mixture refluxing. When the refluxing stopped, the mixture was stirred for another 15 min, and ethyl acetate (53 mL, 0.55 mol) was added dropwise to decompose excess reagent. The mixture was poured onto

ice (300 g) and NH4Cl (85 g), and the ethereal layer was separated and washed with saturated sodium chloride solution (100 mL). The aqueous layer was extracted with dichloromethane (2*100 mL), the extracts were combined with the ether solution and driedwith MgSO4, and the solvent was evaporated. The crude product was distilled under vacuum (bp 112 oC/0.05 Torr) to yield a pure colorless liquid (42.9 g, 94%).

【Roman Popielarz and Donald R. Arnold， J . Am. Chem. Soc. 1990, 112, 3068-3082】

A solution of benzophenone (42 g, 0.2 mol) in ether (400 mL) was added dropwise to a solution of lithium aluminum hydride (35.6 g, 0.93 mol) in ether (1400 mL) and the mixture was bolied under reflux for 6 g. The solution was cooled. Then 36 mL of water was added dropwise. The solid was removed and filtrate was concentrated and the risidue distilled (bp 88-90 at 0.027 mmHg) to afford the product (22 g, 61 %), which on collong solidified。

【Wardrop, J. Chem. Soc. Perkin Trans.1 1976, 1279-1285】

To magnetically stirred trifluoroacetic acid (50 mL) at 0 oC under nitrogen, sodium borohydride (2.0 g, 53 mmol) was carefully added in portion over 45 min. To this slurry a solution of substrate (10 mmol) in dry dichloromethane (40 mL) was added dropwise. As each drop of solution comes in contact with the slurry, a strong coloration (the carbocation) was observed which rapidly disappeared. The rate of addition is governed by the rate of color discharge. After the mixture was stirred at room temperature under nitrogen for typically 20 h, it was quenched with ice cooled aqueous 2 M sodium chloride until alkaline.

After extraction into dichloromethane (3*60 mL), the separated organic layers were combined and washed with saturated sodium carbonate (100 mL). The organic layer was dried over anhydrous magnesium sulfate for 3 h. After filtration the dichloromethane was evaporated off, giving a crude solid which was re-crystallized from ethanol or propan-2-ol.

【James H. P. Utley and Gregor G. Rozenberg Tetrahedron, 2002, 58, 5251-5265】

本文内容非原创，版权归原作者所有，如涉及版权问题，请联系删除。