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No.
12 60 120 traces 84
a
All reactions were carried out on a 1 mmol scale of 2-methylaminopyrimidine (1, R1 = Me) with
1.35 equiv of α-phenacylbromide (2, R2 = Ph) in MeCN (5 Ml); b isolated yield after recrystallization
from MeCN.
Table-1: Investigation of the condensation under conventional heating and
microwave irradiation a
As the transformation of salts (3) into salts (4) is relatively rapid at the temperatures
above 100 °C, the synthesis of salts 3 was conducted at 80 °C. Treatment of
substituted 2-aminopyrimidines (1) with 15 mol % excess of α-bromoketones (2) in
MeCN under microwave irradiation for 30 min generated the intermediate salts (3)
which, in most cases, precipitated from the reaction mixture upon cooling (Table-2).
Reaction progress was monitored by mass-spectrometry. In all cases examined, the
reaction appeared to be complete after 30 min. The cleavage step was performed
under microwave irradiation at 90 °C, using 7 equivalents of hydrazine hydrate. Based
on the data given in (Table-2), the reaction appears to be compatible with both aryl
and alkyl substitutions. All the reactions were clean, smooth, and provided the
products in good and high yields. The compounds were purified by column
chromatography using 5−10% MeOH in CH2Cl2 as the eluent. All the final 2-amino-
1H-imidazoles were characterized by 1 H and 13 C NMR spectroscopy. Their
composition was also confirmed by HRMS.
R1 HN
N
N
H
R 2
Compound
Code
R1 R2 Yield
1 BS-136* CH3 2,4-(di-OCH3) 48
2 BS-137* (benzo[d][1,3]dioxol-6- naphthalen-1-yl 72