2.1.1.7 Reduction of Epoxides
The epoxides are reduced to the corresponding alcohols (Scheme 8). The hydride ion is transferred to the less hindered side of the epoxides.
 |
 |
Scheme 8 |
2.1.2 Lithium Trialkoxyaluminum Hydride [LiAlH(OR)3]
2.1.2.1 Introduction
Though LAH is a powerful reducing agent but is less selective. The reactivity and selectivity can be modified by replacing the three hydride ion with alkoxy groups such as tert-butoxy or ethoxy group. The resulting reagents are less reactive but more selective than LAH.
2.1.2.2 Preparation
The lithium trialkoxyaluminum hydride can be prepared by treating LAH with the alcohol and better to prepare in situ prior to use (Scheme 9).
 |
Scheme 9 |
2.1.2.2.1 Lithium tri-t-Butoxyaluminum Hydride [LiAlH(Ot-Bu)3]
This is less reactive compared to LAH and reduces aldehydes and ketones to alcohols and acid chlorides to aldehydes (Scheme 10). The other functional groups such as acids, amides and nitriles do not react or react very slowly.
 |
Scheme 10 |
2.1.2.2.2 Lithium tri-Ethoxyaluminum Hydride [LiAlH(OEt)3]
Lithium tri-ethoxyaluminum hydride is comparatively stronger reducing agent than lithium tri-t-butoxyaluminum hydride (Scheme 11). It can reduce amides and nitriles to the corresponding aldehydes in good yield.
 |
Scheme 11 |