Key words heterogeneous catalysis - anthranilamide - benzaldehydes - hybrid catalysts
Heterocyclic compounds are vital in daily life, and they play an essential role in
the metabolism of living cells. These compounds contain one or more hetero atoms in
their structure, and they are biosynthesized by plants and animals.[1 ] Moreover, numerous natural products are used as antibiotics such as penicillins
and cephalosporin, and some alkaloids (morphine, vinblastine, and reserpine) comprise
a heterocyclic moiety.[2 ] A large number of heterocyclic compounds show a range of applications in pharmaceuticals,
agrochemicals, and veterinary products.[3 ] Some of the heterocyclic compounds can be used as sanitizers, antioxidants, developers,
copolymers, corrosion inhibitors and dyestuff.[4 ] DNA and RNA compounds also contain heterocyclic bases such as pyrimidines and purines.[5 ]
We have been interested in the synthesis of heterocyclic compounds such as 2-aryl-2,3-dihydroquinazolin-4(1H )-ones, which belong to the family of six-membered heterocycles. In particular, 2,3-dihydroquinazolin-4(1H )-one derivatives have proven to provide a useful framework for bioactive compounds,
as shown in Figure [1 ]. These analogues exhibit significant biological properties that can be effectively
utilized as antitumor, anticancer, herbicidal, diuretic compounds, and in plant growth
regulation.[6 ] Moreover, these compounds are oxidized to the quinazolin-4(3H )-one moiety, which constitutes an important core structure in many natural products.[7 ] Very recently, our group has been developing a synthesis of 2-aryl-2,3-dihydroquinazolin-4(1H )-ones by using a one-pot approach mediated by β-cyclodextrin under aqueous conditions.[8 ] In view of the importance of these heterocycles, several methods were reported for
the synthesis of 2-aryl-2,3-dihydroquinazolin-4(1H )-one derivatives;[9 ] approaches include the use of silica sulfuric acid,[10 ] gallium(III)triflate,[11 ] montmorillonite K-10,[12 ] Amberlyst-15,[13 ] KAl(SO4 )2 ·12H2 O,[14 ] Al(H2 PO4 )3 ,[15 ] zinc(II) perfluorooctanoate [Zn(PFO)2 ],[16 ] MCM-41-SO3 H,[17 ] 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4 ),[18 ] and molecular iodine.[19 ] However, these methods are associated with some limitations such as hazardous organic
solvents, expensive catalysts, low yields, long reaction time, elevated temperature,
non-recyclability, toxic metals, stoichiometric loadings, or low conversions.
Figure 1 Bioactive scaffolds featuring a quinazolin-4(1H )-one moiety
Therefore, it is essential to establish a greener method for the preparation of 2,3-dihydroquinazolin-4(1H )-ones. Fortunately, we have overcome all the limitations noted above and, herein,
we report a novel an efficient green approach to 2-aryl-2,3-dihydroquinazolin-4(1H )-ones through a one-pot protocol using anthranilamide, and several aldehydes in the
presence of [Ce(l -Pro)2 ]2 (Oxa) as heterogeneous catalyst, and EtOH as a green solvent at 50–55 °C (Scheme
[1 ]).
We analyzed [Ce(l -Pro)2 ]2 (Oxa) as an efficient and accessible catalyst for the preparation of 2-aryl-2,3-dihydroquinazolin-4(1H )-one derivatives under mild conditions. The catalyst comprises mild Lewis acid properties,[20 ] is chemically stable, and does not dissociate at high temperatures.
At the beginning of the study, we conducted a model reaction between anthranilamide
and benzaldehyde with neither catalyst nor solvent, at room temperature, and found
that the corresponding product was formed in low yield after several hours of reaction.
Hence, we conducted the reaction in the presence of both [Ce(l -Pro)2 ]2 (Oxa) as catalyst and solvent by using the same starting materials, and the reaction
was found to proceed sluggishly at room temperature with the desired product being
formed in around 62% in 6 hours. To improve the reaction yield, the reaction temperature
was increased from r.t. to 50–55 °C with the same starting materials, and [Ce(l -Pro)2 ]2 (Oxa) was used as catalyst in EtOH as green solvent. Under these conditions we obtained
the desired product in 89% yield within 4–4.5 hours. In addition, we carried out the
present protocol using different catalyst loadings (1.0, 2.5, 5 mol% etc). Thus, 5
mol% catalyst loading was found to form 2-phenyl-2,3-dihydroquinazolin-4(1H )-one with optimal conversion. The yield was unaffected when the catalyst loading
was increased to 20 mol%.
Scheme 1 Synthesis of 2-aryl-2,3-dihydroquinazolin-4(1H )-ones
Table 1 Screening of Solvents for the Synthesis of 2-Phenyl-2,3-dihydroquinazolin-4(1H )-one (3k ; Table [2 ], entry 11)a
Entry
Solvent
T (°C)
Yield (%)b
1
–
–
12c
2
CH2 Cl2
r.t.
54
3
CHCl3
r.t.
56
4
ACN
50
63
5
H2 O
70
67
6
EtOH
r.t.
70
7
EtOH
50–55
89
a Reaction conditions: Anthranilamide (1.0 mmol), benzaldehyde (1.0 mmol), [Ce(l -Pro)2 ]2 (Oxa) (5 mol%).
b Isolated yield.
c In the absence of catalyst and solvent.
The reaction was then performed using several solvents including CH2 Cl2 , CHCl3 , tetrahydrofuran (THF), H2 O and EtOH; we observed that EtOH was a suitable solvent for the preparation of 2-phenyl-2,3-dihydroquinazolin-4(1H )-one (3k ) as shown in Table [1 ]. Subsequent reactions were carried out using similar reaction conditions.
Starting benzaldehydes possessing either electron-donating groups such as -Me, -OMe,
-OH, and -allyloxy, or electron withdrawing groups such as -NO2 , -F, -Cl, and -Br gave excellent yields (Table [2 ]).
Table 2 Synthesis of 2-Aryl-2,3-dihydroquinazolin-4(1H )-ones using [Ce(l -Pro)2 ]2 (Oxa)a
Entry
Aldehyde
Product
Yield (%)b
1
4-methylbenzaldehyde
3a
87
2
4-methoxybenzaldehyde
3b
88
3
4-hydroxybenzaldehyde
3c
87
4
2,5-dimethylbenzaldehyde
3d
86
5
3,4-dihydroxybenzaldehyde
3e
81
6
4-fluorobenzaldehyde
3f
89
7
4-chlorobenzaldehyde
3g
89
8
4-bromobenzaldehyde
3h
88
9
4-nitrobenzaldehyde
3i
96
10
3-nitrobenzaldehyde
3j
90
11
benzaldehyde
3k
89, 62c
12
1-naphthaldehyde
3l
84
13
anthracene-9-carbaldehyde
3m
84
14
3-phenylpropanal
3n
72
15
thiophene-2-carbaldehyde
3o
89
16
4-(allyloxy)benzaldehyde
3p
87
a Reaction conditions: Anthranilamide (1.0 mmol), benzaldehyde (1.0 mmol), [Ce(l -Pro)2 ]2 (Oxa) (5 mol%).
b Isolated yield.
c In the presence of catalyst and solvent at r.t.
Figure 2 Recyclability of the catalyst
Upon completion of the reaction, the reaction mass was cooled to r.t., and the catalyst
was filtered off and cleaned with diethyl ether before drying at 80 °C for 2 h. The
recovered catalyst was reused with the same substrates, and the yields and the catalytic
activity were monitored; the results are shown in Figure [2 ]. In all these reactions the catalyst could be recycled and reused with little loss
of its catalytic activity (Figure [2 ]).
We proposed a mechanism for the formation of 2-aryl-2,3-dihydroquinazolin-4(1H )-one derivatives as shown in Figure [3 ]. Based on the experimental results, the mechanism of the reaction is thought to
proceeded through condensation of aldehyde with anthranilamide, which subsequently
forms an imine intermediate that cyclizes to afford the corresponding 2-aryl-2,3-dihydroquinazolin-4(1H )-one as the desired product, as shown in Figure [3 ].[21 ]
[14 ] SEM images of native (A) and used catalyst (B) are shown in Figure [4 ]; their analysis confirmed that the morphology of the fresh catalyst and the catalyst
after the reaction are similar. IR (C) and X-ray diffraction pattern (D) of the catalyst
are shown in Figure [5 ].
Figure 3 Proposed mechanistic pathway for the synthesis of 2,3-diphenyl-2,3-dihydroquinazolin-4(1H )-one mediated by [Ce(l -Pro)2 ]2 (Oxa)[21 ]
Figure 4 SEM images of native and used catalyst
Figure 5 Catalyst IR (C) and X-ray diffraction pattern (D)
All the products were compared with authentic samples and characterized by 1 H, 13 C NMR, IR and mass spectroscopic analyses.[8 ]
[21 ] All spectral data matched the corresponding data in the literature.
All chemical reagents and solvents were used without specific treatment. The respective
reactions were monitored using thin-layer chromatography (TLC) MACHEREY-NAGEL (SIL
G/UV254 ). The compounds were purified by recrystallization. 1 H and 13 C NMR spectra were recorded in CDCl3 with a Bruker spectrometer (300 MHz, and 75 MHz, respectively). The IR spectra were
recorded with a FT/IR 4100 type A spectrometer (Jasco).
[Ce(l -Pro)2 ]2 (Oxa)[22 ]
l-Proline (2.7 mmol) was dissolved in methanol (15 ml), an aqueous solution of sodium
hydroxide (2.7 mmol in 1 mL) was added at room temperature, and the mixture was stirred
for 10 minutes. Then cerium (III) chloride (1.4 mmol) was added to it, and the reaction
mixture was stirred for 45 minutes. Then a few drops of sodium oxalate solution (0.1
g mL–1 ) were added to it. It was used as a precipitating agent. The semi-solid was centrifuged,
washed with methanol, and dried overnight at 40 °C to obtain a pale yellow semi-solid.
2-(p -Tolyl)-2,3-dihydroquinazolin-4(1H )-one; Typical Procedure[8 ]
[21 ]
2-(p -Tolyl)-2,3-dihydroquinazolin-4(1H )-one; Typical Procedure[8 ]
[21 ]
[Ce(l -Pro)2 ]2 (Oxa) was dissolved in EtOH (10 mL), and anthranilamide (1.0 mmol) and 4-methyl benzaldehyde
(1.0 mmol) were added. The reaction mixture was heated at 50–55 °C until completion
of the reaction as indicated by TLC. The reaction mixture was cooled to r.t., and
the catalyst was separated from the reaction mixture by filtration. The solvent was
evaporated under reduced pressure and the crude compound was purified by column chromatography
(EtOAc/ hexane, 3:7).
Yield: 207 mg (87%); yellow solid; mp 223–225 °C.
IR (KBr): 3310, 3192, 3060, 2924, 2855, 1908, 1662, 1607, 1509 cm–1 .
1 H NMR (300 MHz, CDCl
3
): δ = 7.93 (d, J = 7.2 Hz, 1 H), 7.46 (d, J = 8.3 Hz, 2 H), 7.34–7.23 (m, 3 H), 6.89 (t, J = 7.2 Hz, 1 H), 6.65 (d, J = 7.2 Hz, 1 H), 5.86 (s, 1 H), 5.76 (br. s, 1 H), 4.34 (br. s, 1 H), 2.39 (s, 3 H).
13 C NMR (50 MHz, CDCl
3
): δ = 167.15, 133.99, 129.73, 128.69, 127.29, 119.61, 114.53, 68.84, 29.57.
MS (ESI): m /z = 239 [M + H]+ .
2-(4-Methoxyphenyl)-2,3-dihydroquinazolin-4(1H )-one (3b)[8 ]
2-(4-Methoxyphenyl)-2,3-dihydroquinazolin-4(1H )-one (3b)[8 ]
Yield: 223 mg (88%); light-yellow solid; mp 182–184 °C.
IR (KBr): 3448, 3315, 3183, 2923, 1676 cm–1 .
1 H NMR (300 MHz, CDCl
3
): δ = 7.91 (d, J = 7.2 Hz, 1 H), 7.45 (d, J = 8.3 Hz, 2 H), 7.34–7.23 (m, 3 H), 6.88 (t, J = 7.2 Hz, 1 H), 6.63 (d, J = 7.2 Hz, 1 H), 5.84 (s, 1 H), 5.75 (br. s, 1 H), 4.39 (br. s, 1 H), 3.89 (s, 3 H).
13 C NMR (50 MHz, CDCl
3
): δ = 167.14, 133.97, 129.70, 128.67, 127.24, 119.60, 114.51, 68.83, 56.52.
MS (ESI): m /z = 255 [M + H]+ .
2-(4-Hydroxyphenyl)-2,3-dihydroquinazolin-4(1H )-one (3c)[8 ]
2-(4-Hydroxyphenyl)-2,3-dihydroquinazolin-4(1H )-one (3c)[8 ]
Yield: 208 mg (87%); white solid; mp 278–280 °C.
IR (KBr): 3302, 3187, 3068, 2932, 1668, 1612, 1509, 1486 cm–1 .
1 H NMR (300 MHz, CDCl
3
): δ = 9.33 (br. s, 1 H), 7.75 (d, J = 7.7 Hz, 1 H), 7.37 (d, J = 7.1 Hz, 3 H), 7.22 (t, J = 7.3 Hz, 1 H), 6.83–6.69 (m, 4 H), 6.28 (br. s, 1 H), 5.72 (s, 1 H).
13 C NMR (50 MHz, CDCl
3
): δ = 160.98, 156.32, 146.66, 132.71, 128.07, 118.90, 115.65, 113.89, 65.59.
MS (ESI): m /z = 241 [M + H]+ .
2-(2,5-Dimethylphenyl)-2,3-dihydroquinazolin-4(1H )-one (3d)[8 ]
2-(2,5-Dimethylphenyl)-2,3-dihydroquinazolin-4(1H )-one (3d)[8 ]
Yield: 216 mg (86%); yellow solid; mp 222–224 °C.
IR (KBr): 3312, 3192, 3061, 2924, 2855, 1908, 1662, 1607, 1509 cm–1 .
1 H NMR (300 MHz, CDCl
3
): δ = 7.89 (d, J = 6.9 Hz, 1 H), 7.50 (s, 1 H), 7.30 (t, J = 6.9 Hz, 1 H), 7.06 (s, 3 H), 6.85 (t, J = 6.9 Hz, 1 H), 6.69 (d, J = 7.9 Hz, 1 H), 6.20 (br. s, 1 H), 6.07 (s, 1 H), 2.37 (s, 3 H), 2.30 (s, 3 H).
13 C NMR (50 MHz, CDCl
3
): δ = 163.17, 147.12, 135.70, 133.42, 131.60, 129.05, 127.65, 126.69, 126.00, 125.14,
124.63, 115.84, 113.34, 113.04, 63.55, 19.25, 16.84.
MS (ESI): m /z = 253 [M + H]+ .
2-(3,4-Dihydroxyphenyl)-2,3-dihydroquinazolin-4(1H )-one (3e)[8 ]
[21 ]
2-(3,4-Dihydroxyphenyl)-2,3-dihydroquinazolin-4(1H )-one (3e)[8 ]
[21 ]
Yield: 207 mg (81%); light-yellow solid; mp 288–290 °C.
1 H NMR (300 MHz, CDCl
3
): δ = 8.83 (br. s, 1 H), 7.79–7.56 (m, 2 H), 7.40 (t, J = 7.5 Hz, 1 H), 7.20 (t, J = 7.1 Hz, 1 H),7.03 (s, 1 H), 6.88 (d, J = 8.3 Hz, 1 H), 6.81–6.65 (m, 2 H), 5.64 (s, 1 H), 3.58 (br. s, 2 H).
13 C NMR (50 MHz, CDCl
3
): δ = 162.66, 161.08, 150.89, 147.84, 147.43, 146.84, 146.29, 143.95, 143.64, 143.36,
132.97, 131.90, 130.57, 125.76, 124.97, 124.39, 124.21, 121.77, 118.63, 118.23, 116.38,
115.60, 113.80, 113.50, 113.35, 112.86, 112.46, 64.97.
MS (ESI): m /z = 257 [M + H]+ .
2-(4-Fluorophenyl)-2,3-dihydroquinazolin-4(1H )-one (3f)[8 ]
[21 ]
2-(4-Fluorophenyl)-2,3-dihydroquinazolin-4(1H )-one (3f)[8 ]
[21 ]
Yield: 215 mg (89%); yellow solid; mp 202–204 °C.
IR (KBr): 3300, 3183, 3066, 2929, 1658, 1610, 1508, 1482 cm–1 .
1 H NMR (300 MHz, CDCl
3
): δ = 7.94 (d, J = 8.3 Hz, 1 H), 7.62–7.57 (m, 2 H), 7.37–7.32 (m, 1 H), 7.14 (t, J = 8.3 Hz, 2 H), 6.92 (t, J = 8.3 Hz, 1 H), 6.66 (d, J = 8.3 Hz, 1 H), 5.91 (s, 1 H), 5.78 (br. s, 1 H), 4.34 (br. s, 1 H).
13 C NMR (50 MHz, CDCl
3
): δ = 161.87, 158.69, 146.93, 132.64, 128.29, 128.18, 126.86, 117.83, 114.52, 114.24,
113.75, 66.39.
MS (ESI): m /z = 243 [M + H]+ .
2-(4-Chlorophenyl)-2,3-dihydroquinazolin-4(1H )-one (3g)[8 ]
2-(4-Chlorophenyl)-2,3-dihydroquinazolin-4(1H )-one (3g)[8 ]
Yield: 229 mg (89%); light-yellow solid; mp 196–198 °C.
1 H NMR (300 MHz, CDCl
3
): δ = 7.89 (d, J = 7.1 Hz, 1 H), 7.56 (d, J = 8.0 Hz, 2 H), 7.44 (d, J = 8.9 Hz, 2 H), 7.30 (t, J = 7.1 Hz, 1 H), 6.85 (t, J = 7.1 Hz, 1 H), 6.61 (d, J = 7.1 Hz, 1 H), 5.82 (s, 1 H), 5.72 (br. s, 1 H), 4.30 (br. s, 1 H).
13 C NMR (50 MHz, CDCl
3
): δ = 163.07, 146.44, 139.03, 133.12, 132.21, 130.34, 130.08, 128.30, 127.76, 126.36,
121.04, 116.50, 113.73, 113.36, 65.61.
MS (ESI): m /z = 259 [M + H]+ .
2-(4-Bromophenyl)-2,3-dihydroquinazolin-4(1H )-one (3h)[8 ]
2-(4-Bromophenyl)-2,3-dihydroquinazolin-4(1H )-one (3h)[8 ]
Yield: 265 mg (88%); yellow solid; mp 200–202 °C.
IR (KBr): 3306, 3188, 3060, 2927, 1658, 1607 cm–1 .
1 H NMR (300 MHz, CDCl
3
): δ = 7.90 (d, J = 7.1 Hz, 1 H), 7.54 (d, J = 8.0 Hz, 2 H), 7.43 (d, J = 8.9 Hz, 2 H), 7.31 (t, J = 7.1 Hz, 1 H), 6.88 (t, J = 7.1 Hz, 1 H), 6.63 (d, J = 7.1 Hz, 1 H), 5.84 (s, 1 H), 5.74 (br. s, 1 H), 4.31 (br. s, 1 H).
13 C NMR (50 MHz, CDCl
3
): δ = 163.09, 146.45, 139.05, 133.13, 132.22, 130.37, 130.09, 128.31, 127.77, 126.38,
121.06, 116.51, 113.74, 113.38, 65.60.
MS (ESI): m /z = 303 [M + H]+ .
2-(4-Nitrophenyl)-2,3-dihydroquinazolin-4(1H )-one (3i)[8 ]
2-(4-Nitrophenyl)-2,3-dihydroquinazolin-4(1H )-one (3i)[8 ]
Yield: 258 mg (96%); yellow solid; mp 204–206 °C.
IR (KBr): 3278, 3174, 3032, 2922, 2855, 1647, 1608, 1520, 1461 cm–1 .
1 H NMR (300 MHz, CDCl
3
): δ = 8.31 (d, J = 8.3 Hz, 1 H), 7.96 (m, 1 H), 7.83–7.79 (m, 2 H), 7.41–7.35 (m, 1 H), 7.27 (s, 1 H),
6.98–6.92 (m, 1 H), 6.70 (d, J = 7.5 Hz, 1 H), 6.15 (br. s, 1 H), 6.05 (s, 1 H), 4.43 (br. s, 1 H).
13 C NMR (50 MHz, CDCl
3
): δ = 162.96, 147.60, 146.50, 145.97, 132.46, 126.78, 126.49, 122.25, 116.70, 113.70,
64.89.
MS (ESI): m /z = 270 [M + H]+ .
2-(3-Nitrophenyl)-2,3-dihydroquinazolin-4(1H )-one (3j)[8 ]
2-(3-Nitrophenyl)-2,3-dihydroquinazolin-4(1H )-one (3j)[8 ]
Yield: 242 mg (90%); yellow solid; mp 210–212 °C.
IR (KBr): 3293, 3190, 3072, 2924, 2854, 1654, 1608, 1533 cm–1 .
1 H NMR (300 MHz, CDCl
3
): δ = 8.47 (s, 1 H), 8.30 (d, J = 7.9 Hz, 1 H), 7.97 (t, J = 7.9 Hz, 2 H),7.66 (t, J = 7.9 Hz, 1 H), 7.37 (t, J = 6.9 Hz, 1 H), 6.95 (t, J = 6.9 Hz, 1 H), 6.70 (d, J = 7.9 Hz, 1 H), 6.05 (s, 1 H), 5.91 (br. s, 1 H), 4.42 (br. s, 1 H).
13 C NMR (50 MHz, CDCl
3
): δ = 163.23, 146.98, 146.12, 142.74, 132.59, 132.13, 128.50, 126.66, 122.24, 120.94,
116.99, 114.02, 113.69, 65.08.
MS (ESI): m /z = 270 [M + H]+ .
2-Phenyl-2,3-dihydroquinazolin-4(1H )-one (3k)[8 ]
2-Phenyl-2,3-dihydroquinazolin-4(1H )-one (3k)[8 ]
Yield: 201 mg (90%); light-yellow solid; mp 225–227 °C.
IR (KBr): 3302, 3184, 3061, 2924, 1658, 1612 cm–1 .
1 H NMR (300 MHz, CDCl
3
): δ = 7.94 (d, J = 7.5 Hz, 1 H), 7.61–7.58 (m, 2 H), 7.47–7.44 (m, 2 H), 7.37–7.31 (m, 2 H), 6.91
(t, J = 6.7 Hz, 1 H), 6.66 (d, J = 7.5 Hz, 1 H), 5.91 (s, 1 H), 5.78 (br. s, 1 H), 4.39 (br. s, 1 H).
13 C NMR (50 MHz, CDCl
3
): δ = 164.76, 147.20, 138.50, 134.03, 130.15, 129.11, 128.71, 127.38, 119.68, 114.56,
69.06.
MS (ESI): m /z = 225 [M + H]+ .
2-(Naphthalen-1-yl)-2,3-dihydroquinazolin-4(1H )-one (3l)[8 ]
2-(Naphthalen-1-yl)-2,3-dihydroquinazolin-4(1H )-one (3l)[8 ]
Yield: 230 mg (84%); yellow solid; mp 208–210 °C.
IR (KBr): 3311, 3190, 3061, 2926, 2845, 1910, 1664, 1604, 1506 cm–1 .
1 H NMR (300 MHz, CDCl3 ): δ = 8.11–8.08 (m, 2 H), 8.01 (d, J = 1.5 Hz, 1 H), 7.47 (t, J = 8.3 Hz, 1 H), 7.37–7.25 (m, 3 H), 7.19–7.17 (m, 3 H), 6.88 (t, J = 8.3 Hz, 1 H), 6.61 (d, J = 8.3 Hz, 1 H), 6.10 (s, 1 H).
13 C NMR (50 MHz, CDCl3 ): δ = 163.11, 145.26, 133.86, 130.13, 128.96, 128.71, 128.42, 126.94, 126.74, 119.61,
114.83, 74.62.
MS (ESI): m /z = 275 [M + H]+ .
2-(Anthracen-9-yl)-2,3-dihydroquinazolin-4(1H )-one (3m)[8 ]
2-(Anthracen-9-yl)-2,3-dihydroquinazolin-4(1H )-one (3m)[8 ]
Yield: 272 mg (84%); yellow solid; mp 235–237 °C.
IR (KBr): 3443, 2922, 2852, 1717, 1461, 1375, 1274 cm–1 .
1 H NMR (300 MHz, CDCl
3
): δ = 8.54 (s, 1 H), 8.07–8.01 (m, 3 H), 7.51–7.34 (m, 6 H), 7.24 (m, 2 H), 6.96
(t, J = 6.7 Hz, 1 H), 6.67 (d, J = 8.3 Hz, 1 H), 6.22 (s, 1 H), 4.63 (s, 1 H).
13 C NMR (50 MHz, CDCl
3
): δ = 162.20, 130.86, 129.25, 125.34, 114.71, 63.89.
MS (ESI): m /z = 325 [M + H]+ .
2-Phenethyl-2,3-dihydroquinazolin-4(1H )-one (3n)[8 ]
2-Phenethyl-2,3-dihydroquinazolin-4(1H )-one (3n)[8 ]
Yield: 181 mg (72%); light-yellow solid; mp 209–211 °C.
IR (KBr): 3445, 3315, 3185, 2934, 1673, 1594, 1473, 1235, 1130, 1013, 750 cm–1 .
1 H NMR (300 MHz, CDCl
3
): δ = 7.87 (d, J = 8.1 Hz, 1 H), 7.37–7.21 (m, 4 H), 6.85 (t, J = 7.2 Hz, 1 H), 6.68–6.52 (m, 3 H), 5.75 (br. s, 1 H), 4.91 (t, J = 5.4 Hz, 1 H), 4.12 (br. s, 1 H), 2.89–2.75 (m, 2 H), 2.14–2.10 (q, J = 7.2 Hz, 2 H).
13 C NMR (50 MHz, CDCl
3
): δ = 170.33, 163.57, 147.73, 147.08, 140.02, 132.84, 131.84, 130.75, 127.43, 126.92,
126.26, 124.42, 116.06, 115.78, 114.30, 113.79, 113.23, 63.00, 35.58, 28.36, 27.99.
MS (ESI): m /z = 253 [M + H]+ .
2-(Thiophen-2-yl)-2,3-dihydroquinazolin-4(1H )-one (3o)[8 ]
2-(Thiophen-2-yl)-2,3-dihydroquinazolin-4(1H )-one (3o)[8 ]
Yield: 204 mg (89%); light-yellow solid; mp 210–212 °C.
IR (KBr): 3448, 2923, 2853, 1763, 1651, 1457, 1376 cm–1 .
1 H NMR (300 MHz, CDCl
3
): δ = 7.93 (d, J = 7.5 Hz, 1 H), 7.41–7.32 (m, 2 H), 7.22 (d, J = 3.7 Hz, 1 H), 7.02 (t, J = 4.5 Hz, 1 H), 6.92 (t, J = 7.5 Hz, 1 H), 6.70 (d, J = 8.3 Hz, 1 H), 6.20 (s, 1 H), 6.13 (br. s, 1 H), 4.56 (br. s, 1 H).
13 C NMR (50 MHz, CDCl
3
): δ = 161.95, 132.33, 126.49, 125.26, 124.89, 124.76, 116.93, 113.72, 102.96, 62.28.
MS (ESI): m /z = 231 [M + H]+ .
Anal. Calcd. for C12 H10 N2 OS: C, 62.59; H, 4.38; N, 12.16. Found: C, 62.51; H, 4.24; N, 12.12.
2-[4-(Allyloxy)phenyl]-2,3-dihydroquinazolin-4(1H )-one (3p)[8 ]
2-[4-(Allyloxy)phenyl]-2,3-dihydroquinazolin-4(1H )-one (3p)[8 ]
Yield: 243 mg (87%); light-yellow solid; mp 220–222 °C.
IR (KBr): 3299, 3187, 3061, 1651, 1611, 1509, 1484 cm–1 .
1 H NMR (300 MHz, CDCl
3
): δ = 7.93 (d, J = 6.8 Hz, 1 H), 7.49 (d, J = 8.0 Hz, 2 H), 7.32 (t, J = 8.0 Hz, 1 H), 6.95 (d, J = 8.0 Hz, 2 H), 6.89 (t, J = 8.0 Hz, 1 H), 6.65 (d, J = 8.0 Hz, 1 H), 6.09–6.01 (m, 1 H), 5.84 (s, 1 H), 5.71 (br. s, 1 H), 5.40 (d, J = 17.1 Hz, 1 H), 5.30 (d, J = 9.1 Hz, 1 H), 4.57 (d, J = 5.7 Hz, 2 H), 4.33 (br. s, 1 H).
13 C NMR (50 MHz, CDCl
3
): δ = 161.90, 160.92, 147.36, 133.98, 132.87, 131.76, 129.14, 127.86, 127.15, 125.75,
125.49, 125.27, 119.73, 117.23, 116.88, 114.12, 113.91, 68.03, 67.88, 67.13.
MS (ESI): m /z = 281 [M + H]+ .
