Reduction of Non-aromatic Heterocycles Containing the C N Function

The carbon-nitrogen double bond in cyclic Schiff s bases can be reduced by either borohydride or aluminum hydride ions. Examples in the literature are so numerous that only a few representative examples will be mentioned to indicate the scope of the reaction. 

3-if-Indoles (indolenines) (82) are converted into indolines (83) by sodium borohydride,104 and the related 4a-methyl-l,2,3,4-tetrahydro-4a-H-carbazole (84) was converted into the hexahydro-derivative (85) with lithium aluminum hydride.105 Cervinka106 caused a partial asymmetric conversion of l-methyl-2-phenyl-3,4,5,6-tetrahydro-pyridinium perchlorate (86) to 1-methyl-2-phenylpiperidine (87) by reduction with sodium borohydride in an ethereal solution of (—)-menthol. The carbon-nitrogen double bond of various derivatives of 3,4-dihydroisoquinolines has been reduced by sodium or potassium borohydride using the free bases,107 the proton 

Cervinka, Collection Czech. Chem. Commun. 26, 673 (1961) Chem. Abstr. 55, 15479 (1961). 

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