Re: ORGLIST:Reductive Amination: suggestions

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From: samarium Steiner (neptunium$##$gmx.net)
Date: Thu May 22 2003 - 00:47:49 EDT

Hi,

just try the classical method using ammonium acetate (10eq) as the "amine"
source and NaBH3CN (1.2eq) in MeOH and stirr at r.t. for several hours.

this is an efficient way and are mild conditions.

Another, quite efficient (general) method to transform aldehydes or ketones
into primary amines is to mix the aldehyde with benzylamine (1:1) in EtOH and
hydrogenate at 1-3bar H2 over Pd-C. In your case, there may be problems,
since there is formed a (unsymmetrical) bisbenzylamine intermediate. Which
benzyl-moiety will be removed by H2 depends on the substitutents and on the
substitution pattern. Generally, e-acceptors accelerate and e-donors prevent
debenzylation of an amine (e.g. a benzyl group attached to an amine can selectively
be removed in the presence of a PMB or DMB attached to an amine).

hope this helps, greets

samarium

> Dear all,
>
> I would like to ask you some suggestions regarding a reductive amination
> procedure I would like to perform.
> I have an aromatic ring with these substituents:
> a -CHO group
> a -OCH2COOMe group
> a -OMe group
> a -NO2 group
>
> I need to trasform -CHO into -CH2-NH2 without affecting the NO2 and the
> OCH2COOMe groups
>
> a) a classical way, say NH3 + reductive agent, would trasform the ester
> into
> the amide (right or wrong?) plus adding some by-products. Trasformation
> first
> of the ester into the free acid i guess may overcome this (right or
> wrong?)
> under the same conditions, but i would like to trasform -OCH2COOMe into -
> OCH2COOH (which I need anyway...) at the very end.
>
> b) Would hydrazine + reductive agent work well? Or something like
> allylamine or
> NH2-CH2-Si(Me)3 or NH2-O-Si(Me)3 + reductive agent?? Or, why not,
> something
> LESS TOXIC??
>
> So, my question is: do you know any procedure/reagents/conditions to
> achieve
> the goal? Some updated references on reductive amination will also be well
>
> accepted!
> Thanks v.m.!
> --
> Andrea Giordano
> PhD student, Schultz group
> Gene Expression Program
> EMBL
> Meyerhofstrasse, 1
> 69117 Heidelberg, Germany
> tel: 0049 6221 387 498
> fax: 0049 6221 387 206
>
>
>
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