Reduction of Ketimines, Ketoximes and Hydrazones

Ketimines are reduced to amines very easily by catalytic hydrogenation, by complex hydrides and by formic acid. They are intermediates in reductive amination of ketones (p. 134). An example of the reduction of a ketimine is conversion of 3-aminocarbonyl-2,3-diphenylazirine to the corresponding aziridine by sodium borohydride (yield 73%), by potassium borohydride (yield 71%) and by sodium bis (2-methoxyethoxy) aluminum hydride (yield 71%) [939]. 

Reduction of ketoximes is one of the most useful ways to primary amines. 

Reduction of cyclohexanone oxime with lithium aluminum hydride in tetra-hydrofuran gave cyclohexylamine in 71% yield [809], and reduction of ketoximes with sodium in methanol and liquid ammonia [945] or in boiling ethanol [946] afforded alkyl amines, usually in good to high yields. Stannous chloride in hydrochloric acid at 60° reduced the dioxime of 9,10-phenanthra- 

Oximes of a,/i-unsatiirated ketones, on reduction with lithium aluminum hydride, depending on the structure of the ketoxime and on the reaction conditions, yield unsaturated amines, saturated amines, and sometimes aziridines in fair yields [947], 

Whereas diborane in tetrahydrofuran reduces oximes only at 105-110 , oxime ethers and oxime esters are reduced to amines and alcohols at room temperature in good yields. For example the p-nitrobenzoyl ester of cyclohexanone oxime gave a 67% yield of cyclohexylamine and 81% yield of p-nitrobenzyl alcohol [948]. 

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