Lithium aluminum hydride: A powerful reducing agent

Abstract

(A) Stereoselective reduction: Various syn-1,3-diols were prepared convienently by reduction of β-alkoxy ketones with LiI and LAH (syn/anti selectivity up to >99:1). Here the coordination of LiI gives rise to a syn-selective reducing agent as a consequence of the intervention of a Li +-containing six-membered chelation.5 (Chemical Equation Presented) (B) Reductive removal of a tosylated hydroxy group/epoxide formation/epoxide opening: LAH is also employed in a highly chemo- and regioselective reduction of 2-tosyloxy esters, followed by epoxide formation via an SN2 mechanism and reductive opening of the epoxide.6 (Chemical Equation Presented) (C) Enantioselective reduction of ketones by modified LAH: Highly enantioselective reduction of ketones by chiral-diol modified LAH was successfully demonstrated, with good yields and high ee. 7 (Chemical Equation Presented) (D) Synthesis of amines: LAH is a powerful reducing agent, it reduces azide and nitro functionalities into the corresponding amines in a one-pot process.8 (Chemical Equation Presented) (E) Reduction of amides: LAH reduces both cyclic and acyclic amides to the corresponding amines.9 (Chemical Equation Presented) (F) Epoxide ring opening: LAH attacks the epoxide at the less hindered side and produces the alcohols.10 (Chemical Equation Presented) (G) Reduction of lactones LAH reduces lactones to the corresponding diols.11 (Chemical Equation Presented) (H) Formation of cyclopropane derivatives: A homoallylic mesylate, when subjected to LAH, provided the cyclopropane derivative through homoallylic π-participation.12 (Chemical Equation Presented). © Georg Thieme Verlag Stuttgart.