ORIGINAL PAPER

Synthesis of novel trans-stilbene derivatives containinga 4H-pyran-4-one unit and spectroscopic studiesof two of their malononitrile derivatives

Mahnaz Saraei • Nasrin Valizadeh •

Hakime Ebrahimi-asl

Received: 5 July 2014 / Accepted: 23 September 2014

� Springer-Verlag Wien 2014

Abstract New phosphonium salt was synthesized by

treatment of 2-(4-bromomethylphenyl)-6-phenyl-4H-pyran-

4-one with triphenylphosphine in toluene in 83 % yield.

Treatment of phosphonium salt with substituted benzalde-

hydes such as C6H5–, p-MeC6H4, p-MeOC6H4, p-NO2C6H4,

m-NO2C6H4, o-NO2C6H4, p-ClC6H4, o-ClC6H4, p-BrC6

H4CHO in the presence of NaOH in CH3CN:H2O (1:1 v:v)

afforded corresponding trans-stilbenes in 29–90 % yields.

Two malononitrile derivatives were synthesized and their

spectroscopic properties were investigated using UV–Vis and

fluorescence spectra. The results showed that these com-

pounds exhibited fluorescence emission.

Keywords 4H-Pyran-4-one � Phosphonium salt �Wittig reaction � trans-Stilbene derivatives �Malononitrile derivatives � Fluorescence

Introduction

Stilbene and its derivatives are widely distributed in nature

[1] and have been the subject of much research because of

their wide range of biological activities including anti-

bacterial, antimalarial, antitumor, antioxidant, etc. [2–5]. In

addition, stilbene derivatives have various applications as

dyes, optical brighteners, and whitening agent [6, 7].

The formation of carbon–carbon double bonds is one of

the most important challenges in synthetic organic chem-

istry [8]. It has been a key synthetic step in the preparation

of many natural products and drugs [9–11]. Several

methods for their construction have been described in the

literature [12–16]. Among them, the Wittig reaction is one

of the most popular and powerful methods to construct

carbon–carbon double bonds with a high level of stere-

oselectivity [17]. Since its discovery in 1953 [18], the

Wittig reaction has attracted much attention both from the

synthetic and mechanistic point of view [19–22]. The most

important intermediates for several biologically active

molecules [23–25] and fluoro compounds [26–28] have

been synthesized through the Wittig reaction, in which E-

alkenes are preferred for stabilized ylides, while the Z-

alkenes are the main product when non-stabilized ylides

are employed. The Wittig reagent is prepared by deproto-

nation of the corresponding phosphonium salt obtained by

the quaternization of a phosphine with a halo compound.

The subsequent reaction of the Wittig reagent with a car-

bonyl compound affords corresponding alkene.

Furthermore, 4H-pyran-4-one and 4H-pyran derivatives

are an important class of heterocyclic compounds which have

been extensively studied due to their widespread biological

activities and their presence in naturally occurring compounds

[29–32]. 4-(Dicyanomethylene)-2-methyl-6-[p-(dimethyl-

amino)styryl]-4H-pyran (DCM) is a stilbene derivatives

known as an excellent red emitter for use in OLEDs [33, 34].

As a part of our research interest in synthesis of 4H-

pyran-4-one derivatives [35, 36] herein we report a series

of novel stilbene derivatives with high E-selectivity via the

Wittig reaction of substituted benzaldehydes with phos-

phonium salt containing 4H-pyran-4-one moiety.

Results and discussion

In this work, we have synthesized a series of novel stilbene

derivatives containing a 4H-pyran-4-one unit 3a-3i by the

M. Saraei (&) � N. Valizadeh � H. Ebrahimi-asl

Department of Chemistry, Payame Noor University,

PO BOX 19395-3697, Tehran, Iran

e-mail: mahnaz_saraii@yahoo.com; m_saraei@pnu.ac.ir

123

Monatsh Chem

DOI 10.1007/s00706-014-1321-7

reaction of phosphonium salt 2 with substituted benzalde-

hydes at room temperature. All the synthesized stilbenes

were found to have E-geometry around the carbon–carbon

double bond.

The starting 4H-pyran-4-one was synthesized through

cyclization of related 1,3,5-triketone under acidic condi-

tions [37]. 2-(4-Bromomethylphenyl)-6-phenyl-4H-pyran-

4-one (1) was synthesized by reacting 4H-pyran-4-one with

N-bromosuccinimide (NBS) in dry CCl4 for 48 h in 70 %

yield [38]. Phosphonium salt 2 was synthesized by the

reaction of corresponding bromomethylphenyl pyrone 1

with triphenylphosphine in dry toluene under reflux con-

ditions in 83 % yield.

Stilbenes 3a-3i were synthesized in moderate to good

yields by the reaction of phosphonium salt 2 with substi-

tuted benzaldehydes in the presence of NaOH in

CH3CN:H2O (1:1 v:v) at room temperature (Scheme 1;

Table 1). The structures of synthesized compounds were

confirmed by FT-IR, 1H NMR, 13C NMR, MS, and ele-

mental analysis.

As shown in Scheme 2, we have synthesized two mal-

ononitrile derivatives 4a and 4b containing two cyano

groups as electron acceptors and investigated their spec-

troscopic properties.

The UV–Vis absorption spectra of the compounds 3b, 3c,

4a, and 4b were measured in dilute CHCl3 solution (10-5 M)

as shown in Fig. 1. The absorption spectra of 4a and 4b

exhibited an absorption maximum (kmax) at 398 and 406 nm,

respectively, that can be attributed to p ? p* transitions. The

maximum absorption peaks of the compounds 4a and 4b in

comparison with corresponding compounds 3b and 3c were

showed a red-shift (46 nm) with increase in the absorption

intensities which can be attributed to extended p-conjugated

system in these compounds.

PPh3, toluene

CH3CN:H2O(1:1)

1 2

3a-3i

ArCHO, NaOH, r.t., 1 h

O

O

Ph

Scheme 1

BrO

O

PhPPh3 Br

Reflux, 24 h, 83%

O

O

Ph

Ar

Ar = C6H5-, p-MeC6H4-, p-MeOC6H4-, p-NO2C6H4-, m-NO2C6H4, o-NO2C6H4-,p-ClC6H4-, o-ClC6H4-, p-BrC6H4-

O

O

Ph

Ar

Ar = p-MeC6H4-, p-MeOC6H4-

3b, 3cOPh

Ar

NC CN

CH2(CN)2, Ac2O

Reflux, 140 oC, 24 h

4a, 4b

Scheme 2

Table 1 Wittig reaction of substituted benzaldehydes with phos-

phonium salt 2

Entry Aldehyde Product Yielda/%

1

CHO3a 29

2

CHOMe3b 80

3

CHOMeO3c 68

4

CHOO2N3d 76

5

CHO

O2N

3e 89

6

CHO

NO2

3f 61

7

CHOCl3 g 86

8

CHO

Cl

3 h 83

9

CHOBr3i 90

a Isolated yields

M. Saraei et al.

123

Furthermore, the fluorescence spectra of the compounds

4a and 4b were investigated in dilute CHCl3 solution

(10-5 M) as shown in Fig. 2. The maximum fluorescence

emissions of these compounds are observed at 493 and

521 nm, respectively.

Conclusions

In this study, new phosphonium salt has been synthesized

by the reaction of 2-(4-bromomethylphenyl)-6-phenyl-4H-

pyran-4-one with triphenylphosphine. A series of novel

trans-stilbenes with a high selectivity have been synthe-

sized by the Wittig reaction of substituted benzaldehydes

with phosphonium salt containing 4H-pyran-4-one moiety

in moderate to good yields. Reaction with electron-with-

drawing substituted benzaldehydes was proceeded much

faster. Also, two malononitrile derivatives were synthe-

sized and their spectroscopic properties were investigated

using UV–Vis and fluorescence spectra. The results

showed that the malononitrile derivatives exhibited fluo-

rescence emission.

Experimental

All reagents were purchased from Merck or Fluka com-

panies and used without further purification. The

completion of the reactions and purity of the compounds

were followed by thin layer chromatography (TLC) on

silica gel 60 HF254, with detection by UV light. Crude

products were recrystallized from ethanol. Melting points

were determined on an Electrothermal Barnstead 9200

apparatus (Barnstead, UK). FT-IR spectra were obtained

using KBr pellets on a tensor 27-Bruker spectrometer

(Shimadzu, Japan). 1H NMR, 13C NMR, and 31P NMR

spectra were recorded with a Bruker FT-NMR spectrom-

eter (Germany), at 400, 100, and 161 MHz, respectively, in

CDCl3 and DMSO-d6. Mass spectra were recorded on

direct insert probe Agilent technologies 5975c with triple

axis detector. Elemental analyses were carried out on

Perkin–Elmer CHNS-O Analyzer Model 2400 Series II and

were found to agree favorably with the calculated values.

UV–Vis absorption spectra were measured on a PG-T80

UV/Vis spectrophotometer (UK). Fluorescence spectra

were obtained on a Jasco FP-750 spectrofluorometer

(Japan).

[4-(4-Oxo-6-phenyl-4H-pyran-2-yl)benzyl]triphenylphos-

phonium bromide (2, C36H28BrPO2)

2-(4-Bromomethylphenyl)-6-phenyl-4H-pyran-4-one (1,

0.5 g, 1.47 mmol) was dissolved in 20 cm3 dry toluene.

Then, a solution of 0.58 g triphenylphosphine (2.21 mmol)

in 5 cm3 toluene was added dropwise to the flask. The

reaction mixture was refluxed for 24 h to complete

precipitation. The resulting precipitates were filtered off,

washed with toluene, and dried in vacuum to give

phosphonium salt. The phosphonium salt was used without

further purification. White solid, 0.73 g (83 %); FT-IR

(KBr): �m = 3051, 2869, 2775, 1647 (pyrone-CO), 1612,

1498, 1431, 1384, 1110, 846, 690 cm-1; 1H NMR

(400 MHz, CDCl3): d = 5.73 (2H, d, J = 15.3 Hz,

–CH2–), 6.58 (1H, d, J = 1.9 Hz, pyrone-H), 6.67 (1H, d,

J = 1.9 Hz, pyrone-H), 7.39–7.83 (24H, m, Ar–H) ppm;13C NMR (100 MHz, CDCl3): d = 28.9 (d, J = 46.3 Hz),

110.1, 116.5 (d, J = 85.4 Hz), 124.6 (d, J = 3.3 Hz),

124.7, 128.1, 129.1 (d, J = 12.5 Hz), 129.7 (d,

J = 3.9 Hz), 129.9, 130.4, 130.5, 131.6 (d, J = 5.5 Hz),

133.5 (d, J = 9.9 Hz), 133.9 (d, J = 2.8 Hz), 161.1, 162.1,

Fig. 1 UV–Vis absorption spectra of the compounds 3b, 3c, 4a, and

4b in CHCl3 (concentration 10-5 M)

Fig. 2 Fluorescence emission spectra of the compounds 4a and 4b in

CHCl3 (concentration 10-5M)

Synthesis of novel trans-stilbene derivatives

123

178.9 ppm [39]; 31P NMR (161 MHz, CDCl3):

d = 24.9 ppm.

General procedure for the synthesis of trans-stilbenes

3a-3i

To a solution of 0.1 g phosphonium salt 2 (0.165 mmol)

and substituted benzaldehydes (0.165 mmol) in 8 cm3

CH3CN:H2O (1:1 v:v) was added NaOH powder

(0.165 mmol) at room temperature. The reaction mixture

was stirred for 1 h to complete reaction (monitored by

TLC). The resulting precipitates were collected by filtra-

tion and dried in vacuum to give the alkenes.

(E)-2-Phenyl-6-(4-styrylphenyl)-4H-pyran-4-one

(3a, C25H18O2)

Recrystallized from EtOH. Orange solid, 0.017 g (29 %);

m.p.: 167–168 �C; FT-IR (KBr): �m = 3058, 1649 (pyrone-

CO), 1602, 1502, 1386, 1078, 950, 873, 765 cm-1; 1H

NMR (400 MHz, CDCl3): d = 6.85 (d, 1H, J = 2.2 Hz,

pyrone-H), 6.86 (d, 1H, J = 2.2 Hz, pyrone-H), 7.18 (d,

1H, J = 16.4 Hz, alkene-H), 7.27 (d, 1H, J = 16.4 Hz,

alkene-H), 7.34–7.36 (m, 1H, Ar–H), 7.40–7.44 (m, 2H,

Ar–H), 7.56–7.60 (m, 5H, Ar–H), 7.69 (d, 2H, J = 8.4 Hz,

Ar–H), 7.88–7.91 (m, 4H, Ar–H) ppm; 13C NMR

(100 MHz, CDCl3): d = 111.1, 111.5, 126.0, 126.3,

126.8, 127.1, 127.3, 128.3, 128.8, 129.2, 130.2, 131.1,

131.5, 131.6, 136.7, 140.6, 163.1, 163.3, 180.4 (pyrone-

CO) ppm; MS: m/z (%) = 350 (M?, 27), 69 (100).

(E)-2-Phenyl-6-[4-[2-(4-methylphenyl)vinyl]phenyl]-4H-

pyran-4-one (3b, C26H20O2)

Recrystallized from EtOH. Cream solid, 0.048 g (80 %);

m.p.: 207–208 �C; FT-IR (KBr): �m = 3064, 3026, 2918,

1649 (pyrone-CO), 1600, 1514, 1448, 1419, 1390, 1257,

1022, 948, 828 cm-1; UV–Vis (CHCl3): kmax = 352 nm;1H NMR (400 MHz, CDCl3): d = 2.41(s, 3H, –CH3), 6.84

(d, 1H, J = 2.0 Hz, pyrone-H), 6.85 (d, 1H, J = 2.0 Hz,

pyrone-H), 7.12 (d, 1H, J = 16.0 Hz, alkene-H), 7.22–7.26

(m, 3H, (1H, alkene-H) and (2H, Ar–H)), 7.48 (d, 2H,

J = 8.0 Hz, Ar–H), 7.57–7.58 (m, 3H, Ar–H), 7.67 (d, 2H,

J = 8.0 Hz, Ar–H), 7.87–7.91 (m, 4H, Ar–H) ppm; 13C

NMR (100 MHz, CDCl3): d = 21.6, 111.0, 111.5, 126.0,

126.2, 126.3, 126.8, 126.9, 129.2, 129.6, 129.9, 131.1,

131.4, 131.6, 133.9, 138.4, 140.8, 163.1, 163.3, 180.3

(pyrone-CO) ppm; MS: m/z (%) = 364 (M1, 49), 69 (100).

(E)-2-[4-[2-(4-Methoxyphenyl)vinyl]phenyl]-6-phenyl-4H-

pyran-4-one (3c, C26H20O3)

Recrystallized from EtOH. Yellow solid, 0.043 g (68 %);

m.p.: 211–212 �C; FT-IR (KBr): �m = 3004, 2840, 1649

(pyrone-CO), 1596, 1512, 1446, 1386, 1255, 1176, 1022,

833 cm-1; UV–Vis (CHCl3): kmax = 360 nm; 1H NMR

(400 MHz, CDCl3): d = 3.87 (s, 3H, –OCH3), 6.84 (s, 2H,

pyrone-H), 6.95 (d, 2H, J = 8.4 Hz, Ar–H), 7.03 (d, 1H,

J = 16.4 Hz, alkene-H), 7.21 (d, 1H, J = 16.4 Hz, alkene-

H), 7.52 (d, 2H, J = 8.4 Hz, Ar–H), 7.57–7.58 (m, 3H, Ar–

H), 7.65 (d, 2H, J = 8.4 Hz, Ar–H), 7.86 (d, 2H,

J = 8.4 Hz, Ar–H), 7.89–7.90 (m, 2H, Ar–H) ppm; 13C

NMR (100 MHz, CDCl3): d = 55.4, 110.9, 111.5, 114.3,

125.2, 125.9, 126.3, 126.8, 128.1, 129.2, 129.5, 129.7,

130.7, 131.4, 131.6, 140.9, 159.9, 163.2, 163.3, 180.3

(pyrone-CO) ppm; MS: m/z (%) = 380 (M?, 87), 364

(100).

(E)-2-[4-[2-(4-Nitrophenyl)vinyl]phenyl]-6-phenyl-4H-

pyran-4-one (3d, C25 H17NO4)

Recrystallized from EtOH. Yellow solid, 0.05 g (76 %);

m.p.: 277–278 �C; FT-IR (KBr): �m = 3055, 1643 (pyrone-

CO), 1598, 1508, 1448, 1386, 1338, 1108, 1020, 946,

848 cm-1; 1H NMR (400 MHz, CDCl3): d = 6.86 (d, 1H,

J = 2.0 Hz, pyrone-H), 6.88 (d,1H, J = 2.0 Hz, pyrone-

H), 7.30 (d, 1H, J = 16.4 Hz, alkene-H), 7.35 (d, 1H,

J = 16.4 Hz, alkene-H), 7.57–7.60 (m, 3H, Ar–H),

7.71–7.75 (m, 4H, Ar–H), 7.90–7.92 (m, 2H, Ar–H), 7.93

(d, 2H, J = 8.4 Hz, Ar–H), 8.29 (d, 2H, J = 8.4 Hz, Ar–

H) ppm; 13C NMR (100 MHz, CDCl3): d = 111.5, 111.6,

124.3, 126.0, 126.5, 127.2, 127.7, 128.5, 129.2, 131.4,

131.5, 131.6, 131.8, 139.2, 143.1, 147.2, 162.7, 163.5,

180.2 (pyrone-CO) ppm; MS: m/z (%) = 395 (M?, 2), 69

(100).

(E)-2-[4-[2-(3-Nitrophenyl)vinyl]phenyl]-6-phenyl-4H-

pyran-4-one (3e, C25H17NO4)

Recrystallized from EtOH. Light yellow solid, 0.058 g

(89 %); m.p.: 227–228 �C; FT-IR (KBr): �m = 3068, 1645

(pyrone-CO), 1610, 1512, 1450, 1390, 1346, 1080, 954,

817, 680 cm-1; 1H NMR (400 MHz, CDCl3): d = 6.86 (d,

1H, J = 2.0 Hz, pyrone-H), 6.88 (d, 1H, J = 2.0 Hz,

pyrone-H), 7.28 (d, 1H, J = 16.4 Hz, alkene-H), 7.32 (d,

1H, J = 16.4 Hz, alkene-H), 7.58–7.62 (m, 4H, Ar–H),

7.72 (d, 2H, J = 8.4 Hz, Ar–H), 7.86–7.94 (m, 5H, Ar–H),

8.18 (dd, 1H, J = 1.4, 8.2 Hz, Ar–H), 8.45 (s, 1H, Ar–H)

ppm; 13C NMR (100 MHz, CDCl3): d = 111.4, 111.6,

121.2, 122.7, 126.0, 126.4, 127.5, 128.4, 129.2, 129.8,

130.4, 131.2, 131.5, 131.6, 132.6, 138.6, 139.4, 148.1,

162.8, 163.3, 180.2 (pyrone-CO) ppm; MS: m/z (%) = 395

(M?, 71), 367 (100).

(E)-2-[4-[2-(2-Nitrophenyl)vinyl]phenyl]-6-phenyl-4H-

pyran-4-one (3f, C25H17NO4)

Recrystallized from EtOH. Yellow solid, 0.04 g (61 %);

m.p.: 221–222 �C; FT-IR (KBr): �m = 3064, 1652 (pyrone-

CO), 1608, 1571, 1515, 1448, 1419, 1386, 1342, 1257,

1074, 950, 690 cm-1; 1H NMR (400 MHz, CDCl3):

d = 6.85 (d, 1H, J = 2.0 Hz, pyrone-H), 6.87 (d, 1H,

J = 2.0 Hz, pyrone-H), 7.15 (d, 1H, J = 16.4 Hz, alkene-

H), 7.47–7.51 (m, 1H, Ar–H), 7.58–7.59 (m, 3H, Ar–H),

M. Saraei et al.

123

7.66–7.70 (m, 1H, Ar–H), 7.71–7.78 (m, 3H, (2H, Ar–H)

and (1H, alkene-H)), 7.83 (d, 1H, J = 8.4 Hz, Ar–H),

7.89–7.93 (m, 4H, Ar–H), 8.04 (d, 1H, J = 8.4 Hz, Ar–H)

ppm; 13C NMR (100 MHz, CDCl3): d = 111.4, 111.6,

124.9, 126.0, 126.4, 127.7, 128.3, 128.6, 129.2, 131.2,

131.5, 132.4, 132.6, 133.3, 139.6, 148.1, 162.8, 163.4,

180.2 (pyrone-CO) ppm; MS: m/z (%) = 395 (M?, 9),

57(100).

(E)-2-[4-[2-(4-Chlorophenyl)vinyl]phenyl]-6-phenyl-4H-

pyran-4-one (3 g, C25H17ClO2)

Recrystallized from EtOH. Yellow solid, 0.055 g (86 %);

m.p.: 218–219 �C; FT-IR (KBr): �m = 3065, 1652 (pyrone-

CO), 1600, 1512, 1450, 1419, 1394, 1259, 1087, 948, 835,

684 cm-1; 1H NMR (400 MHz, CDCl3): d = 6.85 (d, 1H,

J = 2.0 Hz, pyrone-H), 6.86 (d, 1H, J = 2.0 Hz, pyrone-

H), 7.15 (d, 1H, J = 16.4 Hz, alkene-H), 7.21 (d, 1H,

J = 16.4 Hz, alkene-H), 7.39 (d, 2H, J = 8.4 Hz, Ar–H),

7.51 (d, 2H, J = 8.4 Hz, Ar–H), 7.57–7.59 (m, 3H, Ar–H),

7.68 (d, 2H, J = 8.4 Hz, Ar–H), 7.88–7.92 (m, 4H, Ar–H)

ppm; 13C NMR (100 MHz, CDCl3): d = 111.2, 111.5,

126.0, 126.4, 127.2, 127.9, 128.0, 129.0, 129.2, 129.7,

130.5, 131.5, 131.6, 134.0, 135.2, 140.2, 163.0, 163.3,

180.2 (pyrone-CO) ppm; MS: m/z (%) = 384.5 (M?, 98),

386.5 ([M ? 2]?, 51), 356 (100).

(E)-2-[4-[2-(2-Chlorophenyl)vinyl]phenyl]-6-phenyl-4H-

pyran-4-one (3 h, C25H17ClO2)

Recrystallized from EtOH. Orange solid, 0.053 g (83 %);

m.p.: 164–165 �C; FT-IR (KBr): �m =3072, 1654 (pyrone-

CO), 1612, 1504, 1446, 1417, 1386, 1026, 950, 759 cm-1;1H NMR (400 MHz, CDCl3): d = 6.85 (d, 1H,

J = 2.0 Hz, pyrone-H), 6.87 (d, 1H, J = 2.0 Hz, pyrone-

H), 7.15 (d, 1H, J = 16.4 Hz, alkene-H), 7.26 (dd, 1H,

J = 1.4, 7.4 Hz, Ar–H), 7.31–7.34 (m, 1H, Ar–H), 7.44

(dd, 1H, J = 1.0, 7.8 Hz, Ar–H), 7.57–7.59 (m, 3H, Ar–H),

7.67 (d, 1H, J = 16.4 Hz, alkene-H), 7.72–7.76 (m, 3H,

Ar–H), 7.91 (d, 4H, J = 8.4 Hz, Ar–H) ppm; 13C NMR

(100 MHz, CDCl3): d = 111.2, 111.5, 126.0, 126.3, 126.6,

127.1, 127.5, 129.2, 129.8, 130.0, 130.6, 131.4, 131.5,

133.8, 134.8, 140.2, 162.9, 163.3, 180.2 (pyrone-CO) ppm;

MS: m/z (%) = 384.5 (M?, 91), 386.5 ([M ? 2]?, 32), 356

(100).

(E)-2-[4-[2-(4-Bromophenyl)vinyl]phenyl]-6-phenyl-4H-

pyran-4-one (3i, C25H17BrO2)

Recrystallized from EtOH. Cream solid, 0.064 g (90 %);

m.p.: 219–220 �C; FT-IR (KBr): �m =3060, 1647 (pyrone-

CO), 1604, 1384, 1070, 1008, 943, 829, 684, 518 cm-1; 1H

NMR (400 MHz, CDCl3): d = 6.84 (d, 1H, J = 2.0 Hz,

pyrone-H), 6.85 (d, 1H, J = 2.0 Hz, pyrone-H), 7.14 (d,

1H, J = 16.4 Hz, alkene-H), 7.19 (d, 1H, J = 16.4 Hz,

alkene-H), 7.44 (d, 2H, J = 8.4 Hz, Ar–H), 7.54 (d, 2H,

J = 8.4 Hz, Ar–H), 7.57-7.59 (m, 3H, Ar–H), 7.67 (d, 2H,

J = 8.4 Hz, Ar–H), 7.88 (d, 4H, J = 8.4 Hz, Ar–H) ppm;13C NMR (100 MHz, CDCl3): d = 111.2, 111.5, 122.2,

126.0, 126.4, 127.2, 128.0, 128.3, 129.2, 129.8, 130.5,

131.5, 131.7, 131.9, 135.7, 140.2, 163.0, 163.4, 180.2

(pyrone-CO) ppm.

General procedure for the synthesis of malononitrile

derivatives 4a and 4b

A solution of 3b or 3c compound (0.27 mmol) and mal-

ononitrile (2.16 mmol) in 6 cm3 acetic anhydride was

heated at 140 �C for 24 h under nitrogen atmosphere and

monitored by TLC. The reaction mixture was cooled to

room temperature and cold water was added to the solu-

tion. The resulting precipitates were filtered off and washed

with water, then dried in vacuum. The crude product was

recrystallized from ethanol.

2-[2-[4-(4-Methystyryl)phenyl]-6-phenyl-4H-pyran-4-yli-

dene]malononitrile (4a, C29H20N2O)

Brown solid, 0.81 g (73 %); m.p.: 162–163 �C; FT-IR

(KBr): �m = 3012, 2972, 2206 (CN), 1635, 1512, 1444,

1427, 1369, 1220, 1089, 929, 837, 680 cm-1; UV–Vis

(CHCl3): kmax = 398 nm; 1H NMR (400 MHz, CDCl3):

d = 2.36 (3H, s, –CH3), 6.60 (1H, d, J = 12.4 Hz, alkene-

H), 6.76 (1H, d, J = 12.4 Hz, alkene-H), 7.10 (2H, d,

J = 8.0 Hz, Ar–H), 7.17 (2H, d, J = 8.0 Hz, Ar–H), 7.21

(1H, d, J = 2.1 Hz, pyrone-H), 7.22 (1H, d, J = 2.1 Hz,

pyrone-H), 7.45 (2H, d, J = 8.4 Hz, Ar–H), 7.58–7.62

(3H, m, Ar–H), 7.79 (2H, d, J = 8.4 Hz, Ar–H), 7.91–7.94

(2H, m, Ar–H) ppm; 13C NMR (100 MHz, CDCl3):

d = 21.3, 104.2, 115.2, 122.7, 126.1, 126.3, 126.6, 126.8,

127.1, 128.0, 128.7, 129.2, 129.8, 130.2, 132.4, 133.0,

137.7, 142.0, 159.9, 160.1, 168.5, 179.9, 184.8 ppm; MS

(EI): m/z (%) = 412 (M?, 52).

2-[2-[4-(4-Methoxystyryl)phenyl]-6-phenyl-4H-pyran-4-

ylidene]malononitrile (4b, C29H20N2O2)

Brown solid, 0.074 g (64 %); m.p.: 247–248 �C; FT-IR

(KBr): �m = 3080, 2921, 2220 (CN), 1639, 1512, 1425,

1259, 1180, 1085, 1022, 931, 804, 680 cm-1; UV–Vis

(CHCl3): kmax = 406 nm; 1H NMR (400 MHz, DMSO-

d6): d = 3.80 (3H, s, –OCH3), 6.95 (1H, s, pyrone-H), 6.97

(1H, s, pyrone-H), 7.16–7.28 (3H, m, (2H, Ar–H) and (1H,

alkene-H)), 7.37 (1H, d, J = 16.4 Hz, alkene-H),

7.60–7.63 (5H, m, Ar–H), 7.74 (2H, d, J = 7.2 Hz, Ar–

H), 8.03–8.07 (4H, m, Ar–H) ppm; 13C NMR (100 MHz,

DMSO-d6): d = 55.7, 103.9, 104.4, 114.7, 115.8, 125.3,

127.0, 127.3, 127.4, 128.1, 128.8, 129.2, 129.3, 129.6,

129.9, 130.2, 130.5, 131.5, 131.9, 156.5, 160.3, 160.4,

169.2 ppm; MS (EI): m/z (%) = 428 (M?, 100).

Acknowledgments The authors are grateful to the Payame Noor

University for financial support.

Synthesis of novel trans-stilbene derivatives

123

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