An Efficient One-Pot Green Protocol for the Synthesis of 5-Unsubstituted 3,4-Dihydropyrimidin-2(1H)-Ones Using Recyclable Amberlyst 15 DRY as a Heterogeneous Catalyst via Three-Component Biginelli-Like Reaction
Table 3
Amberlyst 15 DRY catalyzed synthesis of dihydropyrimidine-2-(1H)-ones/thiones.
Entry
R1
R2
X
Productsa
Yieldb (%)
M.P (°C)
1
C6H5
Et
O
1a
89
205–207
2
4-(CH3O)–C6H4
Et
O
1b
90
202-203
3
4-(NMe2)–C6H4
Et
O
1c
83
254–256
4
4-NO2–C6H4
Et
O
1d
94
212-213
5
4-(Cl)–C6H4
Et
O
1e
91
214–215
6
4-(NO2)C6H4
Me
O
1f
95
237–239
7
4-(CH3O)–C6H4
Me
O
1g
84
192-193
8
C6H5–CH=CH
Et
O
1h
94
231–233
9
3-NO2–C6H4
Et
S
1i
92
206-207
10
4-(CH3O)–C6H4
Et
S
1j
90
154–156
11
C4H4N
Et
O
1k
83
180–182
12
C4H3O
Et
O
1l
85
211–213
13
C4H3S
Et
O
1m
86
201–203
14
C8H6N
Et
O
1n
80
212–214
15
C5H4N
Et
O
1o
91
193-194
16
C5H4N
Et
S
1p
85
168-169
17
C9H6N
Et
O
1q
91
245–247
18
C4H3N2
Et
O
1r
89
255–257
19
C10H7
Et
O
1s
92
182–185
20
C9H5O3
Et
O
1t
89
277–279
aReaction conditions: -ketoester (1.0 mmol), aldehyde (1.0 mmol), and urea/thiourea (1.2 mmol) in dry ethanol (10 mL), ion exchange resin (50 mg) at refluxing temperature. bIsolated yields.
