Carbon-based leaving group capability of Meldrum’s acid in substitution reactions: a new strategy toward the synthesis of 4-phenyl-3, 4-dihydro-2H-benzo[g]chromene-2, 5, 10-triones

Article abstract of DOI:10.1007/s13738-017-1129-6

Abstract: An efficient and straightforward method for the synthesis of new 5,5′-(2-benzylidenemalonyl)bis(2,2-dimethyl-1,3-dioxane-4,6-dione) derivatives by the reaction of Meldrum’s acid and aldehydes under mild reaction conditions is reported. Furthermore, the leaving group potency of Meldrum’s acid molecules toward the synthesis of 3,4-dihydro-2H-benzo[g]chromene-2,5,10-triones is investigated.

Full text of DOI:10.1007/s13738-017-1129-6

J IRAN CHEM SOC
DOI 10.1007/s13738-017-1129-6
ORIGINAL PAPER
Carbon‑based leaving group capability of Meldrum’s acid
in substitution reactions: a new strategy toward the synthesis
of 4‑phenyl‑3, 4‑dihydro‑2H‑benzo[g]chromene‑2, 5, 10‑triones
Milad Pedarpour Vajargahy1 · Minoo Dabiri1 · Ayoob Bazgir1
Received: 25 December 2016 / Accepted: 21 April 2017
© Iranian Chemical Society 2017
Abstract An effcient and straightforward method for
the synthesis of new 5,5′-(2-benzylidenemalonyl)bis(2,2-
dimethyl-1,3-dioxane-4,6-dione) derivatives by the reac-
tion of Meldrum’s acid and aldehydes under mild reaction
conditions is reported. Furthermore, the leaving group
potency of Meldrum’s acid molecules toward the synthe-
sis of 3,4-dihydro-2H-benzo[g]chromene-2,5,10-triones is
investigated.
Graphical Abstract
* Minoo Dabiri
m_dabiri@sbu.ac.ir
* Ayoob Bazgir
a_bazgir@sbu.ac.ir
1
Department of Chemistry, Shahid Beheshti University,
General Campus, Tehran 1983963113, Iran
1 3

J IRAN CHEM SOC
Keywords 3,4-Dihydro-2H-benzo[g]chromene-2,5,10-
triones · Meldrum’s acid arylidene Meldrum’s acid ·
Benzo[g]chromene-triones · Meldrum’s acid · Arylidene
Meldrum’s acid · 2-Hydroxynaphthalene-1,4-dione
and 13CNMR spectra were obtained in DMSO-d6 using
TMS as internal standard.
X‑ray crystallography
The X-ray diffraction measurements were taken with a
STOE IPDS-II diffractometer with graphite-monochro-
mated MoKa radiation. Cell constants and an orienta-
tion matrix for data collection were obtained by least-
squares refnement of diffraction data from 4998 unique
refections for 6a. Data were collected at a temperature
of 298(2) K to a maximum 2q value of 51.988 and in a
series of w scans in 18 oscillations and integrated using
the Stoe X-AREA [27] software package. The data were
corrected for Lorentz and Polarizing effects. The struc-
tures were solved by direct methods and refned on F2
by full-matrix least-squares procedure. All hydrogen
atoms were added at ideal positions and constrained to
ride on their parent atoms, with Uiso(H) = 1.2 Ueq. All
refnements were performed by using the X-STEP32
crystallographic software package [28]. Complete crys-
tallographic data for compound 6a have been deposited
with the Cambridge Crystallographic Data Centre as
supplementary publication No. CCDC-1455796. These
data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
Introduction
The use of environmentally friendly methods and reagents
to deplete undesirable products, harsh work-up procedures,
and evaluation of toxic gases is important in synthetic
chemistry and the chemical industry. Within the recent
years, the development of sustainable, eco-friendly routes
for the construction of medicinally important compounds
has become a signifcant area in the feld of synthesis [1].
Reactions that can be performed in the presence of benign
solvent such as water, ethanol, or in the absence of solvents
are a worthwhile aspect of green chemistry [2, 3].
Meldrum’s acid and its derivatives have garnered a great
deal of interest regarding their value as reagents for chemi-
cal synthesis and due to their unusually high acidities [4–
10], serving as powerful acylating agents in C–C [11–17],
C–O, and C–N bond forming reactions [18, 19] and as
building blocks in the synthesis of numerous natural prod-
ucts. Due to its great acidity (pKa 7.5) [20] and tendency to
regenerate acetone, Meldrum’s acid appears to be an excep-
tional reagent in organic synthesis [21, 22].
Although Knoevenagel condensation of aldehydes and
Meldrum’s acid for the synthesis of arylidene Meldrum’s
acids or 5,5′-(2-benzylidenemalonyl)bis(2,2-dimethyl-
1,3-dioxane-4,6-dione) has been reported in various con-
ditions [23–26], to the best of our knowledge, employ-
ing aldehydes and Meldrum’s acid for the synthesis of
5,5′-(2-benzylidenemalonyl)bis(2,2-dimethyl-1,3-dioxane-
4,6-dione) has not been reported yet. Herein, for the frst
time, the preparation of novel Meldrum’s acid derivatives,
5,5′-(2-benzylidenemalonyl)bis(2,2-dimethyl-1,3-dioxane-
4,6-dione) derivatives, by the reaction of aldehydes and
Meldrum’s acid is reported.
Typical
procedure
for
the
preparation
of
5,5′‑(2‑(2‑Nitrobenzylidene)malonyl)bis(2,2‑dime-
thyl‑1,3‑dioxane‑4,6‑dione) (3a) A mixture of 2-nitroben-
zaldehyde (1 mmol), Meldrum’s acid (3 mmol), and Et3N
(10 mol %) in EtOH (5 mL) was stirred at room tempera-
ture for 24 h. After completion of the reaction, the reaction
mixture was fltered and the precipitate was purifed using
fash chromatography to afford the pure product 3a: Yield
85%. white powder; m.p. 174–175 °C. IR (KBr) (νmax
/
cm−1): 3001, 2930, 2869, 1784, 1744, 1529, 1314. 1H
NMR (300 MHz, DMSO-d6): δH1.71 (s, 6H, 2Me), 1.78 (s,
6H, 2Me), 4.03 (s, 2 CH), 7.61 (d, 3J = 7.5 Hz, 1H arom),
7.74 (t, 3J = 8 Hz, 1H arom), 7.85 (t, 3J = 8 Hz, 1H arom),
8.27 (d, J = 7.5 Hz, 1H arom), 8.85 (1H, s). 13C NMR
3
Experimental
(75 MHz, DMSO-d6): δC 27.3, 27.4, 27.6, 31.1, 105.8,
106.2, 117.9, 124.8, 130.7, 130.8, 131.4, 134.7, 146.8,
156.6, 159.5, 161.7, 164.6, 168.8. MS, m/z: 489 (M+).
Anal. Calcd. for C22H19NO12: C, 53.99; H, 3.91; N, 2.86.
Found: C, 53.91; H, 3.83; N, 2.94%.
All starting materials were obtained from Merck or Acros
and were used without further purifcation. Melting points
were measured on an Electrothermal 9100 apparatus and
are uncorrected. Mass spectra were recorded on a FINNI-
GAN-MAT 8430 mass spectrometer operating at an ion-
ization potential of 70 eV. IR spectra were recorded on
1
a FT-IR 102 MB BOMEM apparatus. H and 13C NMR
5,5′‑(2‑Benzylidenemalonyl)bis(2,2‑dimethyl‑1,3‑diox-
ane‑4,6‑dione) (3b) Yield 80%. White powder; m.p. 164–
165 °C. IR (KBr) (νmax/cm−1): 3001, 2950, 2904, 2860,
spectra were recorded on a BRUKERDRX-300 AVANCE
1
spectrometer at 300.13 and 75.47 MHz, respectively. H
1 3

J IRAN CHEM SOC
1
1775, 1737. H NMR (300 MHz, DMSO-d6): δH 1.72 (s,
powder; m.p. 156–157 °C. IR (KBr) (νmax/cm−1): 3003,
2922, 2860, 1773, 1737, 1537, 1319. H NMR (300 MHz,
1
6H, 2Me), 1.77 (s, 6H, 2Me), 4.03 (s, 2 CH), 7.49 (m, 2H
arom), 7.60 (m, 1H arom), 8.00 (d, 3J = 7.5 Hz, 2H arom),
8.38 (1H, s). 13C NMR (75 MHz, DMSO-d6): δC 27.4,
27.5, 31.1, 105.1, 106.2, 116.2, 128.9, 129.3, 132.3, 133.3,
133.5, 157.0, 160.0, 163.0, 168.8. MS, m/z: 444 (M+).
Anal. Calcd. for C22H20O10: C, 59.46; H, 4.54. Found: C,
59.38; H, 4.44%.
DMSO-d6): δH 1.70 (s, 6H, 2Me), 1.78 (s, 6H, 2Me),
3
4.02 (s, 2H, CH), 7.78 (d, J = 7.5, 1H arom), 8.29 (d,
3
3J = 7.5 Hz, 1H arom), 8.37 (d, J = 7.5 Hz, 1H arom),
8.52 (s, 1H arom), 8.87 (1H, s). 13C NMR (75 MHz,
DMSO-d6): δC 27.4, 27.6, 31.1, 102.8, 106.1, 118.1,
122.8, 123.4, 124.7, 130.2, 133.9, 147.9, 148.4, 154.4,
159.5, 162.6, 168.6. MS, m/z: 489 (M+). Anal. Calcd. for
C25H19NO12: C, 53.99; H, 3.91; N, 2.86. Found: C, 54.12;
H, 4.02; N, 2.77%.
5,5′‑(2‑(2‑bromobenzylidene)malonyl)bis(2,2‑dime-
thyl‑1,3‑dioxane‑4,6‑dione) (3c) Yield 83%. White pow-
der; m.p. 173–174 °C. IR (KBr) (νmax/cm−1): 2999, 2925,
2860, 1784, 1742. 1H NMR (300 MHz, DMSO-d6): δH 1.71
(s, 6H, 2Me), 1.79 (s, 6H, 2Me), 4.03 (s, 2 CH), 7.44–7.46
(m, 2H, arom), 7.63 (m, 1H arom), 7.75 (d, 3J = 7 Hz, 1H
arom), 8.41 (s, 1H). 13C NMR (75 MHz, DMSO-d6): δC
27.4, 27.7, 31.2, 105.7, 106.3, 119.2, 123.7, 127.8, 129.2,
131.9, 132.9, 133.1, 133.6, 155.0, 159.2, 162.0, 164.6. MS,
m/z: 522 (M+). Anal. Calcd. for C22H19BrO10: C, 50.50; H,
3.66. Found: C, 50.39; H, 3.57%.
5,5′‑(2‑(4‑Nitrobenzylidene)malonyl)bis(2,2‑dime-
thyl‑1,3‑dioxane‑4,6‑dione) (3g) Yield 79%. White
powder; m.p. 186–187 °C. IR (KBr) (νmax/cm−1): 3006,
1
2917, 2862, 1772, 1734, 1527, 1317. H NMR (300 MHz,
DMSO-d6): δH 1.72 (s, 6H, 2Me), 1.76 (s, 6H, 2Me), 4.03
3
(s, 2H, CH), 8.06 (d, J = 9.0 Hz, 2H arom), 8.28 (d,
3J = 9.0 Hz, 2H arom), 8.51 (s, 1H). 13C NMR (75 MHz,
DMSO-d6): δC 27.7, 31.1, 102.8, 105.6, 119.6, 123.6,
124.7, 133.0, 139.0, 149.1, 154.3, 159.5, 162.1, 162.6. MS,
m/z: 489 (M+). Anal. Calcd. for C25H19NO12: C, 53.99; H,
3.91; N, 2.86. Found: C, 53.88; H, 4.00; N, 2.77%.
5,5′‑(2‑(3‑Bromobenzylidene)malonyl)bis(2,2‑dime-
thyl‑1,3‑dioxane‑4,6‑dione) (3d) Yield 81%. White pow-
der; m.p. 165–166 °C. IR (KBr) (νmax/cm−1): 3079, 2907,
2811, 1791, 1648. 1H NMR (300 MHz, DMSO-d6): δH 1.71
(s, 6H, 2Me), 1.77 (s, 6H, 2Me), 4.03 (s, 2 CH), 7.46 (t,
5,5′‑(2‑(3‑Hydroxybenzylidene)malonyl)bis(2,2‑dime-
thyl‑1,3‑dioxane‑4,6‑dione) (3h) Yield 87%. White pow-
der; m.p. 126–127 °C. IR (KBr) (νmax/cm−1): 3483, 3004,
3J = 7.5 Hz, 1H arom), 7.75 (d, J = 7.5 Hz, 1H arom),
3
1
7.91 (d, 3J = 7.5 Hz, 1H arom), 8.22 (s, 1H arom), 8.35 (s,
1H). 13C NMR (75 MHz, DMSO-d6): δC 27.4, 27.5, 36.4,
104.8, 105.5, 106.2, 116.2, 122.4, 130.1, 131.7, 133.4,
135.1, 135.9, 155.8, 159.3, 162.6, 163.2. MS, m/z: 522
(M+). Anal. Calcd. for C22H19BrO10: C, 50.50; H, 3.66.
Found: C, 50.61; H, 3.78%.
2910, 2852, 1778, 1738. H NMR (300 MHz, DMSO-d6):
δH 1.71 (s, 6H, 2Me), 1.75 (s, 6H, 2Me), 4.03 (s, 2H, CH),
3
3
6.98 (d, J = 7.5 Hz, 1H arom), 7.31(t, J = 7.5 Hz, 1H
3
arom), 7.38 (d, J = 7.5 Hz, 1H arom), 7.47 (s, 1H arom),
8.25 (1H, s), 9.83 (1H, s, OH). 13C NMR (75 MHz, DMSO-
d6): δC 27.4, 31.1, 105.0, 106.2, 116.0, 119.0, 120.9, 125.0,
130.0, 133.3, 157.1, 157.5, 159.9, 163.1, 164.6, 168.8. MS,
m/z: 460 (M+). Anal. Calcd. for C22H20O11: C, 57.40; H,
4.38. Found: C, 57.50; H, 4.47%.
5,5′‑(2‑(4‑Methylbenzylidene)malonyl)bis(2,2‑dime-
thyl‑1,3‑dioxane‑4,6‑dione) (3e) Yield 87%. White pow-
der; m.p. 195–196 °C. IR (KBr) (νmax/cm−1): 3001, 2948,
2915, 2865, 1774, 1736. H NMR (300 MHz, DMSO-d6):
δH 1.71 (s, 6H, 2Me), 1.75 (s, 6H, 2Me), 2.39 (s, 3H, Me),
1
5,5′‑(2‑(2‑Fluorobenzylidene)malonyl)bis(2,2‑dime-
thyl‑1,3‑dioxane‑4,6‑dione) (3i) Yield 75%. White
powder; m.p. 173–174 °C. IR (KBr) (νmax/cm−1): 3001,
3
4.03 (s, 2H, CH), 7.32 (d, J = 9 Hz, 2H arom), 7.98 (d,
1
3J = 9 Hz, 2H arom), 8.33 (s, 1H). 13C NMR (75 MHz,
DMSO-d6): δC 21.9, 27.4, 37.1, 104.9, 106.2, 114.7, 129.2,
129.6, 129.7, 134.0, 144.9, 157.2, 160.2, 163.2, 164.6. MS,
m/z: 458 (M+). Anal. Calcd. for C23H22O10: C, 60.26; H,
4.84. Found: C, 60.17; H, 4.73%.
2909, 2948, 2910, 2864, 1779, 1737. H NMR (300 MHz,
DMSO-d6): δH 1.71 (s, 6H, 2Me), 1.78 (s, 6H, 2Me), 4.02
(s, 2 CH), 7.29–7.36 (m, 2H arom), 7.57–7.61(m, 1H
3
arom), 7.84 (t, J = 7.5 Hz, 1H arom), 8.34 (s, 1H). 13C
NMR (75 MHz, DMSO-d6): δC 27.5, 27.8, 31.2, 105.4,
106.0, 106.2, 116.1, 116.4, 119.5, 121.2, 124.6, 124.9,
132.6, 134.6, 148.4, 159.7, 162.1, 164.6. MS, m/z: 462
(M+). Anal. Calcd. for C22H19FO10: C, 57.15; H, 4.14.
Found: C, 57.03; H, 4.04%.
5,5′‑(2‑(3‑Nitrobenzylidene)malonyl)bis(2,2‑dime-
thyl‑1,3‑dioxane‑4,6‑dione) (3f) Yield 83%. White
1 3

J IRAN CHEM SOC
5,5′‑(2‑(3‑Fluorobenzylidene)malonyl)bis(2,2‑dime-
thyl‑1,3‑dioxane‑4,6‑dione) (3j) Yield 73%. White pow-
der; m.p. 168–169 °C. IR (KBr) (νmax/cm−1): 3001, 2950,
c = 25.056(6) Å, α = 90o, β = 91.50(2)o, γ = 90o,
V = 1434.6(5) Å3, Z = 4, Dc = 1.409 g.cm−3
,
μ(Mo-Kα)
=
0.099 mm−1
,
crystal dimension of
1
2916, 2862, 1776, 1739. H NMR (300 MHz, DMSO-d6):
0.50 × 0.49 × 0.35 mm. The structure was solved by
using SHELXS. The structure refnement and data reduc-
tion were carried out with SHELXL of the X-Step32
suite of programs. The non-hydrogen atoms were refned
anisotropically by full-matrix least squares on F2 val-
ues to fnal R1 = 0.0608, wR2 = 0.1113, and S = 1.021
with 208 parameters using 3865 independent refection (θ
range = 2.54–29.18). Hydrogen atoms were located from
expected geometry and were not refned.
δH 1.72 (s, 6H, 2Me), 1.78 (s, 6H, 2Me), 4.03 (s, 2H, CH),
3
7.44 (t, J = 9.0 Hz, 1H arom), 7.53–7.60(m, 1H arom),
7.77 (d, 3J = 7.5 Hz, 1H arom), 7.90 (d, 3J = 10.5 Hz, 1H
arom), 8.38 (s, 1H). 13C NMR (75 MHz, DMSO-d6): δC
27.4, 27.6, 31.1, 104.0, 105.3, 106.2, 117.5, 118.7, 119.8,
129.6, 130.8, 134.4, 155.3, 159.8, 162.7, 164.6, 168.8. MS,
m/z: 462 (M+). Anal. Calcd. for C22H19FO10: C, 57.15; H,
4.14. Found: C, 57.07; H, 4.23%.
4‑(P‑tolyl)‑3,4‑dihydro‑2H‑benzo[g]chromene‑2,5,10‑tri-
one (6b) Yield 90%. Yellow powder; m.p. 187–188 °C.
IR (KBr) (νmax/cm−1): 3024, 2919, 2854, 1793, 1680,
1656, 1634, 1594. 1H NMR (300 MHz, DMSO-d6): δH 2.27
5,5′‑(2‑(4‑Chlorobenzylidene)malonyl)bis(2,2‑dime-
thyl‑1,3‑dioxane‑4,6‑dione) (3k) Yield 77%. White pow-
der; m.p. 193–194 °C. IR (KBr) (νmax/cm−1): 3005, 2950,
1
1
2909, 2863, 1780, 1740. H NMR (300 MHz, DMSO-d6):
(s, 3H, Me), 2.89 (bd, 1H, CH), 3.35 (dd, J = 16.5 Hz,
δH 1.71 (s, 6H, 2Me), 1.76 (s, 6H, 2Me), 4.03 (s, 2 CH),
2J = 7.0 Hz CH), 4.56 (d, 3J = 7.5 Hz, CH), 7.12–7.18 (m,
4H arom), 7.87–7.90 (m, 2H arom), 8.00 (m, 1H arom),
8.11 (m, 1H arom). 13C NMR (75 MHz, DMSO-d6): δC
21.0, 34.6, 36.3, 125.6, 126.5, 126.6, 127.2, 130.0, 131.4,
131.5, 134.8, 135.1, 136.9, 137.3, 152.5, 166.0, 177.6,
183.1. MS, m/z: 318 (M+). Anal. Calcd. For C20H14O4: C,
75.46; H, 4.43. Found: C, 75.35; H, 4.52%.
3
3
7.57 (d, J = 8.0 Hz, 2H arom), 8.02 (d, J = 8.0 Hz, 2H
arom), 8.37 (s, 1H). 13C NMR (75 MHz, DMSO-d6): δC
27.4, 27.5, 31.1, 105.2, 106.2, 116.6, 129.0, 131.2, 131.4,
135.0, 138.1, 155.6, 159.9, 162.8, 164.6. MS, m/z: 478
(M+). Anal. Calcd. for C22H19ClO10: C, 55.18; H, 4.00.
Found: C, 55.26; H, 4.09%.
Typical procedure for the preparation of 4‑Phenyl‑3,4‑di-
hydro‑2H‑benzo[g]chromene‑2,5,10‑trione (6a) A mix-
ture of 2-hydroxynaphthalene-1,4-dione (5) (1 mmol),
5,5′-(2-benzylidenemalonyl)bis(2,2-dimethyl-1,3-dioxane-
4,6-dione) (3b) (1 mmol), and Et3N (10 mol %) in EtOH
(5 mL) was stirred at room temperature for 24 h. After
completion of the reaction (monitored by TLC), the reac-
tion mixture was fltered and the precipitate was recrystal-
lized from chloroform/ethanol to afford the pure product
(6a) [29]: Yield 86%. Yellow powder; m.p. 207–208 °C. IR
(KBr) (νmax/cm−1): 3095, 3083, 3006, 2901, 1790, 1679,
1660, 1642, 1592. 1H NMR (300 MHz, DMSO-d6): δH 2.89
(bd, 1H, CH), 3.38 (dd, J = 16.0 Hz, J = 7.0 Hz CH),
4.60 (d, 3J = 7.5 Hz, CH), 7.27–7.32 (m, 4H, arom), 7.89–
7.91 (m, 2H arom), 7.99–8.02 (m, 1H arom), 8.10–8.13 (m,
1H arom). 13C NMR (75 MHz, DMSO-d6): δC 35.0, 36.3,
125.4, 126.5, 126.7, 127.4, 128.1, 129.6, 131.5, 134.8,
135.1, 140.1, 152.6, 166.0, 177.6, 183.2. MS, m/z: 304
(M+). Anal. Calcd. for C19H12O4: C, 74.99; H, 3.98. Found:
C, 75.11; H, 4.08%.
4‑(3‑Bromophenyl)‑3, 4‑dihydro‑2H‑benzo[g]
chromene‑2,5,10‑trione (6c) Yield 81%. Yellow pow-
der; m.p. 214–215 °C. IR (KBr) (νmax/cm−1): 3075, 3046,
1
2905, 1791, 1681, 1657, 1637, 1590. H NMR (300 MHz,
1
DMSO-d6): δH 2.90 (bd, 1H, CH), 3.38 (dd, J = 16.0 Hz,
3
2J = 7.0 Hz CH), 4.60 (d, J = 7.5 Hz, CH), 7.26–7.36
(m, 2H arom), 7.47 (d, 3J = 7.5 Hz, 1H arom), 7.61 (s, 1H
arom), 7.89–7.91 (m, 2H arom), 7.99–8.01 (m, 1H arom),
8.10–8.13 (m, 1H arom). 13C NMR (75 MHz, DMSO-d6):
δC 34.7, 36.2, 122.8, 124.3, 126.4, 126.6, 130.3, 131.0,
131.5, 131.6, 134.8, 135.0, 142.8, 153.0, 165.8, 177.5,
183.2. MS, m/z: 381 (M+). Anal. Calcd. for C19H11BrO4:
C, 59.55; H, 2.89. Found: C, 59.46; H, 2.78%.
1
2
4 ‑ ( 2 ‑ N i t ro p h e n y l ) ‑ 3 , 4 ‑ d i h y d ro ‑ 2 H ‑ b e n z o [ g ]
chromene‑2,5,10‑trione (6d) Yield 89%. Yellow powder;
m.p. 221–222 °C. IR (KBr) (νmax/cm−1): 3073, 2929, 2854,
1
1798, 1683, 1650, 1592, 1523, 1344. H NMR (300 MHz,
1
DMSO-d6): δH 2.94 (bd, 1H, CH), 3.56 (dd, J = 16.2 Hz,
3
2J = 8.7 Hz CH),, 4.95 (d, J = 7.5 Hz, CH), 7.51–7.64
(m, 3H arom),, 7.90–7.92 (m, 3H arom), 8.07–8.14 (m,
2H arom). 13C NMR (75 MHz, DMSO-d6): δC 31.6, 35.2,
123.6, 125.9, 126.4, 126.7, 129.3, 129.8, 131.3, 131.5,
134.1, 134.8, 134.9, 135.1, 148.6, 153.4, 165.2, 177.4,
183.0. MS, m/z: 349 (M+). Anal. Calcd. for C19H11NO6:
X‑ray data for 6a
C19H12O4, M = 304.29 g/mol, monoclinic system,
space group P21/n, a = 5.4870(13), b = 10.4386(18),
1 3

J IRAN CHEM SOC
Table 1 Optimization of the reaction conditions
Table 2 Synthesis of products 3a–k
Product 3
X
Yield (%)
Entry
Solvent
Catalyst
Yield (%)
a
b
c
d
e
f
2-NO2
H
85
80
83
81
87
83
79
87
75
73
77
1
2
3
4
5
6
7
8
9
Toluene
CH2Cl2
MeCN
H2O
Et3N
31
Et3N
38
Et3N
62
2-Br
3-Br
4-Me
3-NO2
4-NO2
3-OH
2-F
Et3N
Trace
57
MeOH
EtOH
EtOH
EtOH
EtOH
Et3N
Et3N
85
g
h
i
p-TSA
H2SO4
Catalyst free
52
56
49
j
3-F
2-nitro benzaldehyde (1 mmol), Meldrum’s acid (3 mmol), cat. (10%
mol), room temperature, reaction time = 24 h
k
4-Cl
C, 65.33; H, 3.17; N, 4.01 Found: C, 65.42; H, 3.28; N,
3.92%.
4H arom), 8.16–8.19 (d, 3J = 7.5 Hz, 2H arom). 13C NMR
(75 MHz, DMSO-d6): δC 31.2, 34.9, 124.1, 124.6, 126.2,
126.5, 126.6, 129.0, 131.5, 134.9, 135.1, 147.4, 147.7,
153.0, 165.5, 177.5, 183.1. MS, m/z: 349 (M+). Anal.
Calcd. for C19H11NO6: C, 65.33; H, 3.17; N, 4.01. Found:
C, 65.45; H, 3.30; N, 3.88%.
4 ‑ ( 3 ‑ N i t ro p h e n y l ) ‑ 3 , 4 ‑ d i h y d ro ‑ 2 H ‑ b e n z o [ g ]
chromene‑2,5,10‑trione (6e) Yield 85%. Yellow pow-
der; m.p. 235–236 °C. IR (KBr) (νmax/cm−1): 3085, 3035,
2930, 2852, 1800, 1685, 1659, 1637, 1532, 1346. 1H NMR
(300 MHz, DMSO-d6): δH 2.99 (bd, 1H, CH), 3.43 (dd,
1J = 16.2 Hz, 2J = 7.8 Hz CH), 4.80 (d, 3J = 7.5 Hz, CH),
4‑(3‑Hydroxyphenyl)‑3,4‑dihydro‑2H‑benzo[g]
chromene‑2,5,10‑trione (6g) Yield 93%. Yellow powder;
m.p. 243–244 °C. IR (KBr) (νmax/cm−1): 3391, 3051, 3019,
3
3
7.62 (t, J = 7.5 Hz, 1H arom), 7.79 (d, J = 7.5 Hz, 1H
arom), 7.86–7.91 (m, 2H arom), 7.98–8.00 (m, 1H arom),
8.10–8.15 (m, 2H arom), 8.27 (s, 1H arom). 13C NMR
(75 MHz, DMSO-d6): δC 31.1, 34.7, 122.8, 123.1, 124.1,
126.5, 126.6, 131.0, 131.5, 134.1, 134.8, 135.0, 142.3,
148.7, 153.0, 165.7, 177.5, 183.2. MS, m/z: 349 (M+).
Anal. Calcd. for C19H11NO6: C, 65.33; H, 3.17; N, 4.01.
Found: C, 65.24; H, 3.25; N, 4.11%.
1
2919, 1784, 1670, 1660, 1640, 1594. H NMR (300 MHz,
DMSO-d6): δH 2.85 (bd, 1H, CH), 3.41 (d, 1H, CH Over-
lapped with solvent), 4.49 (d, 3J = 7.5 Hz, CH), 6.65–6.72
3
(m, 3H arom), 7.12 (t, J = 7.5 Hz, CH), 7.92 (bs, 2H
arom), 8.01 (bs, 1H arom), 8.11 (bs, 1H arom), 9.49 (s, 1H,
OH). 13C NMR (75 MHz, DMSO-d6): δC 34.8, 36.1, 114.1,
114.9, 117.8, 125.6, 126.5, 126.7, 130.6, 131.3, 131.4,
134.9, 135.2, 141.3, 152.3, 158.1, 166.0, 177.6, 183.1. MS,
m/z: 320 (M+). Anal. Calcd. for C19H12O5: C, 71.25; H,
3.78. Found: C, 71.14; H, 3.66%.
4 ‑ ( 4 ‑ N i t ro p h e n y l ) ‑ 3 , 4 ‑ d i h y d ro ‑ 2 H ‑ b e n z o [ g ]
chromene‑2,5,10‑trione (6f) Yield 86%. Yellow pow-
der; m.p. 216–217 °C. IR (KBr) (νmax/cm−1): 3075, 2999,
2937, 2858, 1782, 1731, 1678, 1640, 1520, 1347. 1H NMR
(300 MHz, DMSO-d6): δH 2.95 (bd, 1H, CH), 3.47 (bd,
4‑(2‑Fluorophenyl)‑3,4‑dihydro‑2H‑benzo[g]
chromene‑2,5,10‑trione (6h) Yield 86%. Yellow pow-
der; m.p. 227–228 °C. IR (KBr) (νmax/cm−1): 3064,
3010, 2923, 1796, 1682, 1658, 1640, 1594. 1H NMR
3
1H, CH Overlapped with solvent), 4.77 (d, J = 7.5 Hz,
3
CH), 7.65–7.68 (d, J = 7.5 Hz, 2H arom), 7.82–7.99 (m,
1 3

J IRAN CHEM SOC
(300 MHz, DMSO-d6): δH 2.81 (bd, 1H, CH), 3.42 (dd,
1 J = 15.9 Hz, 2J = 8.1 Hz CH), 4.75 (d, 3J = 7.5 Hz, CH),
8.09–8.10 (m, 1H arom). 13C NMR (75 MHz, DMSO-d6):
δC 34.4, 36.1, 124.8, 126.5, 126.6, 129.4, 129.5, 131.4,
131.5, 132.7, 134.8, 135.0, 139.0, 152.7, 165.8, 177.5,
183.1. MS, m/z: 338 (M+). Anal. Calcd. for C19H11ClO4:
C, 67.37; H, 3.27. Found: C, 67.46; H, 3.17%.
3
7.10 (t, J = 6 Hz, 1H arom), 7.22–7.35 (m, 3H arom),
7.88 (bs, 2H arom), 7.96 (s, 1H arom), 8.09 (s, 1H arom).
13C NMR (75 MHz, DMSO-d6): δC 29.6, 34.8, 116.3 (d,
2J = 21.7 Hz), 123.6, 125.3, 126.4, 126.6, 126.8, 129.4,
130.3 (d, 3J = 7.8 Hz), 131.4, 134.8, 135.1, 153.0, 160.2 (d,
1J = 243.8 Hz), 165.3, 177.4, 183.0. MS, m/z: 322 (M+).
Anal. Calcd. for C19H11FO4: C, 70.81; H, 3.44. Found: C,
70.73; H, 3.53%.
Results and discussion
Initially, the reaction of 2-nitro benzaldehyde 2a
(1 mmol) and Meldrum’s acid 1 (3 mmol) in the pres-
ence of various catalysts and solvents was investigated
(Table 1). As shown in Table 1, the use of ethanol as a
green solvent at room temperature in the presence of
Et3N (10 mol %) as base catalyst allowed the formation
of 5,5′-(2-(2-nitrobenzylidene)malonyl)bis(2,2-dimethyl-
1,3-dioxane-4,6-dione) (3a) in 85% yield (Table 1, entry
6).
4‑(4‑Chlorophenyl)‑3,4‑dihydro‑2H‑benzo[g]
chromene‑2,5,10‑trione (6i) Yield 82%. Yellow pow-
der; m.p. 214–215 °C. IR (KBr) (νmax/cm−1): 3102, 3019,
1
2936, 1792, 1680, 1656, 1637, 1593. H NMR (300 MHz,
1
DMSO-d6): δH 2.89 (bd, 1H, CH), 3.37 (dd, J = 16.2 Hz,
3
2J = 7.5 Hz CH), 4.61 (d, J = 7.5 Hz, 1H), 7.38 (s, 4H
arom), 7.89–7.90 (m, 2H arom), 7.98–7.99 (m, 1H arom),
Scheme 1 Proposed mecha-
nism for the synthesis of
products 3
1 3

J IRAN CHEM SOC
According to the optimized conditions, vari-
ous aldehydes 2a–k were selected to react with Mel-
decomposed to acetone and H2O by the reaction with sec-
ond molecule of Meldrum’s acid to afford intermediate 5.
The intermediate 5 reacts with the other molecule of Mel-
drum’s acid 1 and after elimination of water [30] affords
5,5′-(2-benzylidenemalonyl)bis(2,2-dimethyl-1,3-diox-
ane-4,6-dione) derivatives 3 (Scheme 1).
drum’s acid
1 under optimal conditions to give
5,5′-(2-benzylidenemalonyl)bis(2,2-dimethyl-1,3-diox-
ane-4,6-dione) 3a–k in good yields (Table 2).
All the products were characterized by IR, mass, NMR
spectra, and elemental analysis. The mass spectrum of 3a
shows the molecular ion peak at m/z 489. The IR spectrum
of 3a exhibits distinct absorption bands due to carbonyl
Fillion et al. for the frst time reported the leav-
ing group ability of Meldrum’s acid in hydrogenoly-
sis of unstrained carbon–carbon σ-bonds. They have
described substitution reactions employing Meldrum’s
acid and 5-methyl Meldrum’s acid as carbon-based leav-
ing groups which transform unstrained quaternary and
tertiary benzylic Csp3–Csp3 bonds into Csp3–X bonds
(X=C, H, N) [31, 32]. So, we investigated the leav-
ing group ability of Meldrum’s acid in the reaction of
5,5′-(2-benzylidenemalonyl)bis(2,2-dimethyl-1,3-diox-
ane-4,6-dione) derivatives 3 with 2-hydroxynaphtha-
lene-1,4-dione 5 and obtained 4-phenyl-3,4-dihydro-
2H-benzo[g]chromene-2,5,10-trione derivatives 6a–j in
good isolated yields (Table 3). Up to now, the synthesis
of benzo[g]chromene-2,5,10-trione has reported via a
three-component reaction of aldehyde, Meldrum’s acid,
and 2-hydroxynaphthalene-1,4-dione [33–35]. Fortu-
nately, herein for the frst time, we report the leaving
group capability of Meldrum’s acid in an organic reac-
tion which includes functionalization of Csp2–Csp3
bond into Csp2–X bond (X=O). This observation brings
about the fact that Meldrum’s acid is not only capable of
1
groups at 1784 and 1744 cm−1. The H-NMR spectrum of
3a consisted of two sharp singlet for the methyl groups of
Meldrum’s acid (δH 1.71, 1.78 ppm), one sharp singlet (δH
4.03 ppm) for two methine groups of two Meldrum’s acid.
Four aromatic hydrogens were observed as two doublets
(δH 7.61 and 8.27 ppm, J = 8.0 Hz) and two triplet (δH
7.74 and 7.85 ppm, J = 8.0 Hz), and fnally, the alkylidene
hydrogen was appeared as a sharp singlet (δH 8.85 ppm).
The 1H-decoupled 13C-NMR spectrum of 3a shows 18 dis-
tinct signals, in agreement with the proposed structure.
As of yet, in spite of great deal of research around the
interesting properties related to Meldrum’s acid, there
has not been any reports in the literature which indi-
cates that Meldrum’s acid could react with aldehyde
with 3:1 molar ratio. Surprisingly, and in continuation
of the studies around the unique characteristics of the
Meldrum’s acid, we observed for the frst time that one
molecule of arylidene Meldrum’s acid 4 (formed in situ
by the reaction of Meldrum’s acid 1 and aldehyde 2) was
Table 3 Synthesis of benzo[g]chromene-2,5,10-trione 6
Product 6
X
Yield (%)
a
b
c
d
e
f
H
86
90
81
4-Me
3-Br
2-NO2
3-NO2
4-NO2
3-OH
2-F
89
85
86
93
86
82
g
h
i
4-Cl
1 3

J IRAN CHEM SOC
Conclusion
In summary, we have described a facile method for the
synthesis of novel 5,5′-(2-benzylidenemalonyl)bis(2,2-
dimethyl-1,3-dioxane-4,6-dione) derivatives with superb
leaving group ability of Meldrum’s acid molecules for the
synthesis of benzo[g]chromene-triones. The reactions in
both categories are easy to perform in good yields by using
inexpensive starting materials. The operational simplicity,
combined with environmental friendly aspect, makes this
new heterocycle synthetic strategy highly attractive and
promising for the development of compounds of poten-
tial synthetic interest. Finally, the arylidene framework
presented here is likely to be inserted to organic struc-
tures regarding their potential bidentate leaving group
capability.
Fig. 1 ORTEP diagram of product 6a
decomposing to acetone and CO2 [36], but can also serve
as a potential leaving group in organic synthesis.
1
The structures of products 6 were established by IR, H
NMR, and 13CNMR spectroscopy. The structure of 6a was
confrmed by a single-crystal X-ray analysis (Fig. 1).
A possible mechanism for the formation of 6 is
proposed in Scheme 2. Michael-type addition reac-
tion of the 2-hydroxynaphthalene-1,4-dione 5 and the
5,5′-(2-benzylidenemalonyl)bis(2,2-dimethyl-1,3-dioxane-
4,6-dione) 3 followed by cyclization and losing one mole-
cule of Meldrum’s acid leads to intermediate 8. The nucleo-
philic attack of H2O on the carbonyl group of intermediate
8 followed by the extrusion of the second Meldrum’s acid’s
molecule produces intermediate 9. Finally, the decarboxy-
lation reaction of 9 creates product 6 (Scheme 2).
Acknowledgements We gratefully acknowledge fnancial support
from the Research Council of Shahid Beheshti University.
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1 3

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1 3