LiAlH from nitriles

With few exceptions, organometalUcs add only once to nitriles (Section 8.6.4). Only if there is a very strong Lewis acid present to activate the anionic intermediate of the first nucleophilic attack will a second addition take place. An example of this second addition is the reduction of nitriles with LiAlH4, which proceeds all the way to the amine (Section 8.6.3). The AIH3 formed from the initial reduction acts as a Lewis acid to catalyze the second addition. This second addition can be prevented by using one equivalent of a less reactive aluminum hydride like LiAlH(OEt)3 or diisobutylaluminum hydride, [(CH3)2CHCH2l2AlH. The reactions in the acidic water workup are the reverse of imine formation (Section 10.5.2). 

Reduction Nitriles and amides can be easily reduced to alkylamines using lithium aluminium hydride (LiAlH ). In the case of a nitrile, a primary amine is the only possible product. Primary, secondary, and tertiary amines can be prepared from primary, secondary and tertiary amides, respectively. 

Various other reductive methods have been applied to amino-alcohol synthesis. (S)-(-)-3-Piperidinol was synthesised from both L-glutamic acid and (S)-malic acld. The routes involved cycli-sations of amino-alcohols in which the amino moiety was established by azide and nitrile reductions with H /Pd-C and LiAlH j respectively. Acyl cyanides were reduced to optically active amino-... 

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