Lithium aluminum hydride LiAlH derivatives

Scheme 9.113. A representation of the reduction of the cyclohexene derivative (cis-l-methyl-3-oxa-2,4-dioxobicyclo[4.3.0]-7-nonene, cis-l-methyl-cyclohex-4-ene-l,3-dicarboxyUc acid anhydride) with lithium aluminum hydride (LiAlH,) to produce the corresponding lactone, cM-l-methyl-3-oxa-4-oxobicyclo[4.3.0]-7-nonene (cw-l-methyl-l-hydroxymethylcyclohex-4-...

Cha et al[12] have reported that acyloxy-9-BBN derivatives are also readily reduced by lithium aluminum hydride in the presence of pyridine, and the reduction stops at the aldehyde stage. Further, Cha and coworkers have found that lithium tris(diethylamino) aluminum hydride (LTDEA), readily prepared [13] from the reaction of LiAlH and 3 equiv of diethylamine in THE (Eq. 7.2), reduces the acyloxy group to the corresponding aldehyde in fair yield. However, in the presence of 2 equiv of pyridine the reduction stops at the aldehyde stage, and hydrolysis affords excellent yields of aldehydes (Eq. 7.3, Table 7.5) [13]. 

The conversion of carboxylic acid derivatives (halides, esters and lactones, tertiary amides and lactams, nitriles) into aldehydes can be achieved with bulky aluminum hydrides (e.g. DIBAL = diisobutylaluminum hydride, lithium trialkoxyalanates). Simple addition of three equivalents of an alcohol to LiAlH, in THF solution produces those deactivated and selective reagents, e.g. lithium triisopropoxyalanate, LiAlH(OPr )j (J. Malek, 1972). 

The most accessible synthesis of organohydrogermanes was based on the reduction of the corresponding organohalogermanes (R4 nGcX , n = 1-3) with complex hydrides such as LiAlH4173 183 230 237 318 335-342, NaBH4276 343, and LiAlH(OBu-t)3322,344. The less reactive lithium hydride and deuteride have been also recommended for this reduction270,345, and sodium hydride in the presence of boron or aluminum derivatives was also used. 

---