H. Tavakol and S. Zakery, Preparation of secondary amines from one-pot reduction of ketimines  13^th Iranian seminar of Organic Chemistry, Bu-Ali Sina University, Hamedan, Iran, 6-8 September 2006

Abstract

Preparation of amines is one of the useful methods in synthetic organic chemistry because of wide range of amine usage in synthesis [1] and industry [2]. However, most of these methods are limited because of some problems such as polyalkylation, oxidation of nitrogen and so on. Notwithstanding these problems, one of these methods is very useful and unlimited; this named aminoreduction [3] that by using this method, we can synthesize amines from reduction of imines or iminium salts.

Although we saw many papers about reductive amination reactions of aldehydes in the literature, but we read only a few report about reductive amination of ketones. Because the condensation reaction between ketones and amines is not a facile reaction with high yield while the condensation reaction between aldehydes and amines is very simple. For example, we succeeded at doing it in ten minutes in lithium perchlorate/diethyl ether solution in previous researches [4]. So that we decide to use borane-tetrahydrofuran complex for reductive amination of ketones. In our reaction, we first prepare imines from condensation reaction between ketones and amines then reduced it to corresponding amines. Both of two steps, the preparation of imines and reduction of it, can be carried out in one vessel as a one-pot synthesis and in presence of lithium perchlorate as a catalyst in diethyl ether solution. The reaction was preceded smoothly at room temperature by using various ketones and amines in 14 hours with good yield (scheme 1).