Lithium borohydride LiBH

On the other hand, the number of highly reactive chemicals that advance from the sta of laboratory curiosities to commercial items is constantly increasing, Some of these are sodium hydride (NaH), lithium aluminum hydride (LiAlH ), lithium borohydride (LiBH ), aluminum and beryllium borohydride, Al(BH4)3 and BefBH ), the sodium salt of nitromethane sodium methane nitronate or if one prefers sodium nitro methanate (HjCNOgNa), - and barium carbide (BaCg)/ all of which can flame on contact with water. Again, it must be stressed that particle size and other conditions of exposure may determine whether there is flaming or merely a violent reaction on exposure to water, air, or both. 

The final push to biotin itself required a reduction of the methyl ester with lithium borohydride (LiBH,), treatment with hydrogen bromide (HBr) to generate a thio-phanium bromide salt, which underwent reaction with diethyl malonate to a diester. The latter was not isolated but was hydrolyzed directly to the corresponding dicar-boxylic acid (barium hydroxide), which, on acidification, underwent decarboxylation to yield biotin. 

Alkyl borohydrides with even greater steric hindrance but with similar reactivity and selectivity to the Selec-trides, were prepared from trisiamylborane (siamyl = Me2CH2CHMe- s tri-scc-isoamyl, sec. 5.2.A). Lithium trisiamylborohydride [LiBH(CHMeCHMe2)] and the potassium salt [KBH(CHMeCHMe2)], are similar to the L- and the K-Selectrides and are called LS-Selectride and KS-Selectride, respectively. in Bonjoch s synthesis of aeruginosin 298-A, LS-Selectride reduction of 157 gave 158 in 53% yield. 

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