With LiAIHj

Stereoselective reduction of a y-hydroxy ketone. Reaction of the y-liydroxy ketone 1 with LiAIHj. ZnBHi. or NaBHj yields about equal amounts of the two possible diols. However, reduction 4 ith Li(C,H,),BH (2 cquiv.) yields only one product (2) in yield. The high stereoi-icicctivity is attributed to formation of a chelated boron intermediate that favors attack by the hydride from the (3-facc. The diol (2) is converted by TsCI into ancistrofuran (3), a ddfensive secretion of certain termites. 

NoH, LiAIHJ. For instance, they can act as reducing agents toward many organic compounds and are capable of hydrogenating aikynes and alkenes. Thus their H ligands are intermediate between the strictly hydridic hydrogens in the saline hydrides and the protonic hydrogens in compounds with nonmetals (e.g.. HCI, NH3). 

Asymmetric reduction of ketones. Chiral ketals 2, obtained by reaction of 1 with prochiral ketones, are reduced diastereoselectively to 3 by several aluminum hydride reagents, the most selective of which is dibromoalane (LiAIHj-AIBr, 1 3). Oxidation and cleavage of the chiral auxiliary furnishes optically active alcohols (4) in optical yields of 78-96% ee (equation 1). 

Masters reports that CO can be converted into ethene in high selectivity by treating nicial carbonyls such as Ru3(C0)ii. M(CO)6 (M=Cr.. Mo, W) with Allis and LiAIHj (49J. 

P configuration as it proceeds with retention when SiHCls, SiH2Ph2 and other hydrosilanes are used. LiAIHj or Si2Cl6 are also possible reductants, but inversion sometimes occurs, especially with disilanes (equation (1)). 

Reaction with alkali metals 8, 4.6.7 Reaction with FefCOls/LiAIHj 8, 4.8.4.4.3 Reaction with (f/ -CsHjIFetCOliCHi 8,... 

Precaution Highly flamm. dangerous fire and explosion hazard avoid heat, flame incompat. with oxidizers violent reaction with AIH, and LiAIHj explosions possible with nitric acid, oxygen, ozone may form explosive peroxides may generate electrostatic charge containers may rupture or explode if exposed to heat Hazardous Decomp. Prods. Heated to decomp., emits acrid smoke and irritating fumes... 

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