Re: ORGLIST: imine reduction

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From: Krupa (krupa_shukla$##$yahoo.com)
Date: Mon Jun 16 2008 - 00:02:45 EDT


hi bhushan
reductive amination using sodium cyanoborohydride works best under acidic conditions. make sure you are doing reaction under acidic conditions (pH = 4-5). under acidic conditions imine will be much more electrophilic than aldehyde and so reduction will be preferentially for imine. sodium borohydride is not selective. protection of aldehyde as acetal  under acidic condition might hydrolyze imine . so it may not be good idea i believe. however, if your imine is derived from ketone, you might get lucky protecting aryl aldehyde only without touching imine. lastly, below is ref for paper where it was possible to do imine reduction exclusively in presence of aromatic ketone and ester. another paper did using nickel catalyst. check it out.
Tetrahedron Lett, 42, 2001, 2525-2527
Organic Lett, 8, 2006, 139-142
good luck!
krupa
 

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Today's Topics:

   1. Imine reduction (Bhushan Deodhar)

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Message: 1
Date: Sat, 7 Jun 2008 17:26:58 -0400
From: "Bhushan Deodhar" <bsdeodhar$##$gmail.com>
Subject: ORGLIST: Imine reduction
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Dear Members ,

                        I am trying to reduce a imine selectively in
presence of an aryl aldehyde which is part of the same molecule , iam
trying to use sodium cyanoborohydride for the same,but after i do the
work up i see that the aryl aldehyde also gets reduced to Ar-OH ,so
please help me on the above,can i use sodium borohydride to do the
same ,replies will be highly appreciated.

-- 
Regards,

Bhushan

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