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Helvetica Chimica Acta – Vol. 95 (2012)
Table 5. Synthesis of 3,4-Dihydropyrimidin-2(1H)-one or -thione Derivatives in the Presence of
Al(NO3)3 · 9 H2O as Oxidant Catalyst (cf. Scheme)a)
Entry
R1
R2
X
Time [min]
Yield [%]b)
1
2
3
4
5
6
7
8
9
Ph
Et
Et
Et
Et
Me
Me
Me
Me
Me
Et
O
O
O
O
O
O
O
O
O
S
10
30
20
90
30
90
20
45
30
15
10
120
90
80
89
80
80
83
92
98
98
82
86
80
4-MeOꢀC6H4
4-BrꢀC6H4
3-NO2ꢀC6H4
4-MeOꢀC6H4
3-NO2ꢀC6H4
4-BrꢀC6H4
4-FꢀC6H4
4-FꢀC6H4
Ph
10
11
12
4-BrꢀC6H4
Et
Et
S
O
PhCH¼CH
a) Reaction conditions: alcohol (1 mmol) and Al(NO3)3 · 9 H2O (1.5 mmol) at 808; then urea (1.5 mmol)
and b-keto ester (1 mmol) at 808. b) Yield refers to the isolated product. The products were characterized
by comparison of their spectroscopic and physical data with those of samples synthesized by reported
procedures.
Experimental Part
Typical Procedure: Synthesis of Ethyl 1,2,3,4-Tetrahydro-6-methyl-2-oxo-4-phenylpyrimidine-5-
carboxylate (Table 5, Entry 1). A mixture of BnOH (1 mmol, 108 mg) and Al(NO3)3 · 9 H2O (1.5 mmol,
562 mg) was heated at 808 for 15 min in a test tube (TLC monitoring). After completion of the oxidation
process, ethyl acetoacetate (1 mmol, 105 mg) and urea (1.5 mmol, 90 mg) were added to the mixture,
which was heated with stirring at 808. The reaction was completed within 10 min. After cooling to r.t.,
96% EtOH (ca. 10 ml) was added under vigorous stirring. The almost pure product was gradually
precipitated. The precipitate was filtered, washed with cold EtOH (5 ml), and dried under vacuum; ethyl
1,2,3,4-tetrahydro-6-methyl-2-oxo-4-phenylpyrimidine-5-carboxylate (468 mg, 90%). M.p. 202 – 2048
[18]: 200 – 2028).
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