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imidazoles, where the addition of a suitable nitrogen nucleophile is followed by the
elimination of an activated leaving group such as a halogen or alkyl sulfoxide or
sulfone. This method has been applied with limited success to electron-poor
imidazoles or when fluorine is the leaving group. 4,15 An interesting synthetic route to
functionalized 2-AI's, which were difficult to obtain by other methods, has been
achieved using a base catalyzed rearrangement of 3-amino-1,2,4-oxadiazoles. 16
Another type of heterocyclic rearrangement involves the reaction of 2-aminooxazoles
with ammonia or formamide. 17 Most recently, the synthesis of 2-amino-4(5)-(αhydroxyalkyl)imidazoles
has been demonstrated where 2-AI was reacted with
aldehydes under neutral conditions. 18
The microwave-assisted procedure for the synthesis of 1,4,5-substituted 2aminoimidazoles
(Scheme-1) is two-step protocol based on the cyclocondensation of
2-aminopyrimidines and bromocarbonyl compounds at 130-150 °C, followed by the
cleavage of the intermediary imidazo[1,2-a]pyrimidin-1-ium salts with an excess of
hydrazine.
3.2 Reaction Scheme
Scheme-1
N
N
+
N
H
Br O
H
H 2N
N
N
R 1
R 2
R 1
R 2
MeCN
MW
80 °C, 30 min
MeCN
64% N2H4 MW
100 °C, 10 min
Br
N
N
N
N
N R1 OH
R 2
PPA, 150 °C
aq. HClO4 N R 1
R 2
ClO 4