Organic Reactions Volume 4 - Sciencemadness Dot Org

PREPARATION OF AMINES BY REDUCTIVE ALKYLATION 195
methylations even when both the alkyl groups of the secondary amine
are secondary, as in the following example. 18 In contrast, the alkylation
CH3
Pt I
CH3CH2CHNHCHCH2CH3 + CH2O + H2 —> CH3CH2CHNCHCH2CH3 + H2O
CH3 C2Hs CH3 C2HS
(64%)
of diisopropylamine with propionaldehyde gives only a 26% yield, and
that of di-sec-butylamine with heptaldehyde only a 6% yield. However,
Pt
[(CHs)2CH]2NH + CH3CH2CHO + H2 —> [(CHS)2CH]2NCH2CH2CH3 + H2O
(26%)
[CH3CH2CH(CH3)]2NH + CH3(CH2)BCHO + H2 A
[CH3CH2CH(CH3)]2N(CH2)6CH3 + H2O
(6%)
good yields are obtained with the higher aliphatic aldehydes when the
secondary amine contains only primary alkyl groups.
Most of the preparations of this type have been carried out with
hydrogen and platinum catalyst; there are a few examples of the use of
nickel catalyst and of chemical reductions (see Table XI).
The only recorded alkylation of a secondary aliphatic amine with an
aromatic aldehyde is the preparation, in unspecified yield, of benzyldimethylamine
from dimethylamine, benzaldehyde, hydrogen, and platinum.
73
Only poor yields (up to 47%) are obtained in the preparation of
tertiary amines from aliphatic secondary amines and ketones. The
yields decrease with increasing size and complexity of the groups attached
to the nitrogen atom of the amine or the carbonyl group of the
ketone. These effects are shown in Tables VII and VIII, p. 207.
From Secondary Aromatic Amines and Aldehydes and Ketones.
Simple alkylanilines can be alkylated in good yields (55-93%) by treatment
with formaldehyde or acetaldehyde and zinc and acid. Higher
aliphatic aldehydes and aromatic aldehydes have not been tested in
similar preparations. The only recorded synthesis of a tertiary amine
from an arylalkylamine and a ketone is that employing methylaniline
and methyl ethyl glyoxal. 28
C6H5NHCH3 + CH3COCOCH2CH3 + H2 —> CH3CHCOCH2CH3
I
C6H5NCH3
r Pd