Synthesis of substituted tetrahydrochromenes by the reactions of α, β-unsaturated cyanoesters with dimedone/1,3-cyclohexanedione

Article abstract of DOI:10.1080/00397911.2010.515346

Ethyl esters of 2-cyano-3-arylacrylic acid 1a-d (a=4-CH₃-C ₆H₄-, b=4- N(CH₃)₂-C ₆H₄-, c=2-CH₃O-C₆H₄-, d=2-Cl-C₆H₄-) reacted

Full text of DOI:10.1080/00397911.2010.515346

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Synthesis of Substituted
Tetrahydrochromenes by the Reactions
of α,β-Unsaturated Cyanoesters with
Dimedone/1,3-Cyclohexanedione
M. Giasuddin Ahmed a , U. K. R. Romman a , Kawsari Akhter a
,
Khorshada Jahan a , M. Nazmul Hasan Bhuiyan a & M. Ershad Halim a
a Department of Chemistry, University of Dhaka, Dhaka, Bangladesh
Version of record first published: 29 Jun 2011.
To cite this article: M. Giasuddin Ahmed, U. K. R. Romman, Kawsari Akhter, Khorshada Jahan, M.
Nazmul Hasan Bhuiyan & M. Ershad Halim (2011): Synthesis of Substituted Tetrahydrochromenes
by the Reactions of α,β-Unsaturated Cyanoesters with Dimedone/1,3-Cyclohexanedione, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry,
41:19, 2822-2827
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Synthetic Communications1, 41: 2822–2827, 2011
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.515346
SYNTHESIS OF SUBSTITUTED TETRAHYDROCHROMENES
BY THE REACTIONS OF a,b-UNSATURATED CYANOESTERS
WITH DIMEDONE/1,3-CYCLOHEXANEDIONE
M. Giasuddin Ahmed, U. K. R. Romman, Kawsari Akhter,
Khorshada Jahan, M. Nazmul Hasan Bhuiyan, and
M. Ershad Halim
Department of Chemistry, University of Dhaka, Dhaka, Bangladesh
GRAPHICAL ABSTRACT
Abstract Ethyl esters of 2-cyano-3-arylacrylic acid 1a–d (a ¼ 4-CH3-C6H4-, b ¼ 4-
N(CH3)2-C6H4-, c ¼ 2-CH3O-C6H4-, d ¼ 2-Cl-C6H4-) reacted with 5,5-dimethyl-1,3-
=
cyclohexanedione (2p,
Y
CH3), and 1e–g (e ¼ 4-CH3-C6H4-, f ¼ 2-CH3O-C6H4-,
=
g ¼ 2-Cl-C6H4-) reacted with 1,3-cyclohexanedione (2q, Y H) in the presence of alcoholic
sodium ethoxide to give the corresponding ethyl esters of 2-amino-7,7-dimethyl-5-oxo-
4-aryl-5,6,7,8-tetrahydro-4H-chromene-3-carboxylic acid 4a–d and 2-amino-5-oxo-4-aryl-
5,6,7,8-tetrahydro-4H-chromene-3-carboxylic acid 4e–g. The structures of the compounds
4a–g were confirmed by their ultraviolet, infrared, 1H NMR, 13C NMR, and mass spectral
data and elemental analyses.
Keywords 4H-Chromene; 1,3-cyclohexanedione; 5,5-dimethyl-1,3-cyclohexanedione;
a,b-unsaturated cyanoesters
INTRODUCTION
Synthesis of chromenes and its derivatives has been a subject of considerable
interest during past decades because of their usefulness as biologically active
agents.[1,2] Reports are available for the biological and pharmacological properties
of substituted 4H-chromenes, such as spasmolytic, diuretic, anti-coagulant,
anti-cancer,[3] anti-ancaphylactia,[4] and molluscicidal activity.[5] They are also used
Received April 6, 2010.
Address correspondence to M. Giasuddin Ahmed, Department of Chemistry, University of Dhaka,
Dhaka 1000, Bangladesh. E-mail: mgahmed1@gmail.com
2822

SUBSTITUTED TETRAHYDROCHROMENES
2823
for the treatment of neurodegenerative disease, AIDS-associated dementia, and
Down syndrome as well as for schizophrenia and mycolonus. Besides, polysubsti-
tuted 4H-chromenes constitute the structural unit of many natural products,[6] and
2-amino-4H-chromenes are useful as photoactive materials.[7] Thus, several methods
have been reported for the synthesis of these compounds.[8–15] However, many of
these methods were associated with use of hazardous organic solvents, poor yields
of products, and lack of general applicability; particularly, synthesis of substituted
4H-chromene was rarely addressed. This prompted us to develop a convenient
method for the synthesis of 4-aryl-4H-chromene derivatives, and we report herein
the synthesis of 4-aryl-4H-chromene derivatives via a tandem Knoevenagel and
cyclocondensation reaction using sodium ethoxide as catalyst.
a,b-Unsaturated cyanoesters 1a–g were prepared via Knoevenagel conden-
sation of the corresponding aldehydes with ethyl cyanoacetate in the presence of a
base catalyst as reported in the literature.[16] Compounds 1a–g were reacted with
dimedone=1,3-cyclohexanedione 2p–q in the presence of sodium ethoxide in ethanol
to give tetrahydro-4H-chromenes 4a–g (Scheme 1). The structures of 4a–g were
Scheme 1. Synthesis of tetrahydro-4H-chromenes 4a–g.

2824
M. G. AHMED ET AL.
1
confirmed with the help of their ultraviolet (UV), Infrared (IR), H NMR, 13C
NMR, mass spectrum, and elemental analyses. The formation of 4a–g may be
explained by the initial formation of 1:1 adduct 3a–g, which presumably underwent
subsequent cyclization.
EXPERIMENTAL
Melting points were determined on an Electrothermal micromelting-point
apparatus and uncorrected. The UV spectra were recorded using a Shimadzu
UV-160A spectrophotometer. IR spectra were recorded using a Shimadzu IR-
470A spectrophotometer. The 1H NMR and 13C NMR spectra were taken in CDCl3
with tetramethylsilane (TMS) as an internal standard on a Bruker 400-MHz spectro-
photometer. Mass spectra were carried out using a Jeol JMS-HX 110A instrument.
General Procedure
A mixture of a,b-unsaturated cyanoester 1a-g (5 mmol), dimedone=1,3-cyclo-
hexanedione 2p–q (5 mmol), 5% sodium ethoxide in dry ethanol (1.5 ml), and dry
ethanol (25 ml) was refluxed for 12–15 h. The progress of the reaction was followed,
and purity of the product was checked by thin-layer chromatographic (TLC)
silica-gel plates using CHCl3 as eluting solvent. The reaction mixture was cooled
to room temperature, and the volume was reduced by evaporation. It was then neu-
tralized with 0.1 M HCl acid and extracted with ether (3 ꢀ 25 ml). The ether extract
was dried over anhydrous Na2SO4 and evaporated in a rotary vacuum evaporator.
A solid mass was obtained, which was recrystallized from hot ethanol.
2-Amino-7,7-dimethyl-5-oxo-4-(4-methylphenyl)-5,6,7,8-
tetrahydro-4H-chromene-3-carboxylic Acid Ethyl Ester, 4a
Yield 92%; white crystalline solid; mp 160–162 ꢁC; Rf value in TLC 0.56 (neat
chloroform); IR (KBr) (nmax, cmꢂ1): 3395, 3280 (N-H), 1680, 1650 (C O), 1610,
=
=
1510 (C C stretching of phenyl), 1350 (C-N stretching), 1270, 1190 (C-O stretching);
1H NMR d (in ppm): 7.14 (d, J ¼ 8.0 Hz, ArH, 2H), 6.99 (d, J ¼ 8.0 Hz, ArH, 2H),
6.14 (br s, NH2, 2H), 4.66 (s, C4-H, 1H), 4.02 (q, J ¼ 8.0 Hz, -CH2CH3, 2H), 2.40 (s,
methylene protons at C-6, 2H), 2.25 (s, ArCH3, 3H), 2.15 (d, J ¼ 16.40 Hz, C8-H,
1Hax), 2.13 (d, J ¼ 16.40 Hz, C8-H, 1Heq), 1.17 (t, J ¼ 8.0 Hz, -CH2CH3, 3H),
1.08 (s, CH3 at C-7, 3H), 0.97 (s, another CH3 at C-7, 3H); 13C NMR d (in ppm):
=
196.4 (C O), 169.1 (C-2), 161.2 (–COOCH2CH3), 158.3 (C-9), 142.8, 135.4, 128.5
(2C), 128.0 (2C) (6C-aromatic), 117.0 (C-10), 81.0 (C-3), 59.6 (COOCH2CH3),
50.8 (C-6), 40.7 (C-8), 33.4 (C-4), 32.2 (C-7), 29.1 (CH3 at C-7), 27.5 (another
CH3 at C-7), 21.0 (ArCH3), 14.2 (COOCH2CH3); MS: m=z 355.11 (Mþ). Anal. calcd.
for C21H25NO4: C, 70.98; H, 7.04; N, 3.94. Found: C, 70.80; H, 7.03; N, 3.91.
2-Amino-4-(4-N,N-Dimethylaminophenyl)-7,7-dimethyl-5-oxo-
5,6,7,8-tetrahydro-4H-chromene-3-carboxylic Acid Ethyl Ester, 4b
Yield 70%; white solid; mp 155–157 ꢁC; Rf value in TLC 0.60 (neat chloro-
form); IR (KBr) (nmax, cmꢂ1): 3400, 3280 (N-H), 1680, 1640 (C O), 1610, 1510
=

SUBSTITUTED TETRAHYDROCHROMENES
2825
1
=
(C C stretching of phenyl), 1350 (C-N stretching), 1275, 1190 (C-O stretching); H
NMR: d (in ppm): 7.13 (d, J ¼ 8.0 Hz, ArH, 2H), 6.99 (d, J ¼ 8.0 Hz, ArH, 2H), 6.21
(s, NH2, 2H), 4.66 (s, C4-H, 1H), 4.05 (q, J ¼ 7.10 Hz, -CH2CH3, 2H), 2.40 (s, meth-
ylene protons at C-6, 2H), 2.25 (s, NCH3, 6H), 2.23 (d, J ¼ 13.60 Hz, C8-H, 1Hax),
2.17 (d, J ¼ 13.60 Hz, C8-H, 1Heq), 1.16 (t, J ¼ 7.10 Hz, -CH2CH3, 3H), 1.07 (s, CH3
13
=
at C-7, 3H), 0.96 (s, another CH3 at C-7, 3H); C NMR d (in ppm): 196.3 (C O),
169.6 (C-2), 161.2 (COOCH2CH3), 158.3 (C-9), 142.8, 135.3, 128.5 (2C), 128.0 (2C)
(6C-aromatic), 117.0 (C-10), 80.7 (C-3), 59.5 (COOCH2CH3), 50.8 (C-6), 40.6 (C-8),
33.3 (C-4), 32.1 (C-7), 29.0 (CH3 at C-7), 27.3 (another CH3 at C-7), 20.9–20.6
[N(CH3)2], 14.1 (COOCH2CH3). MS: m=z 384.08 (Mþ). Anal. calcd. for
C22H28N2O4: C, 68.75; H, 7.29; N, 3.64. Found: C, 63.95; H, 5.88; N, 3.66.
2-Amino-4-(2-methoxyphenyl)-7,7-dimethyl-5-oxo-5,6,7,8-
tetrahydro-4H-chromene-3-carboxylic Acid Ethyl Ester, 4c
Yield 70%; white crystalline solid; mp 153–154 ꢁC; Rf value in TLC 0.69 (neat
chloroform); IR (KBr) (nmax, cmꢂ1): 3450, 3400 (N-H), 1690, 1640 (C O), 1590,
=
=
1505 (C C stretching of phenyl), 1360 (C-N stretching), 1270, 1190 (C-O stretching);
1H NMR d (in ppm): 7.35 (d, J ¼ 7.70 Hz, ArH, 1H), 7.15–7.05 (m, ArH, 1H),
6.88–6.80 (m, ArH, 1H), 6.75 (d, J ¼ 8.40 Hz, ArH, 1H), 6.15 (br s, NH2, 2H),
4.80 (s, C4-H, 1H), 4.0 (q, J ¼ 7.80 Hz, -CH2CH3, 2H), 3.75 (s, OCH3, 3H), 2.45
(d, J ¼ 14.20 Hz, C6-H, 1Hax), 2.35 (d, J ¼ 14.20 Hz, C6-H, 1Heq), 2.20 (d,
J ¼ 15.40 Hz, C8-H, 1Hax), 2.15 (d, J ¼ 15.40 Hz, C8-H, 1Heq), 1.20 (t, J ¼ 7.80 Hz,
Hz, -CH2CH3, 3H), 1.10 (s, CH3 at C-7, 3H), 0.95 (s, another CH3 at C-7, 3H); MS:
m=z 371.20 (Mþ). Anal. calcd. for C21H25NO5: C, 67.92; H, 6.79; N, 3.77. Found: C,
67.73; H, 6.74; N, 3.75.
2-Amino-4-(2-chlorophenyl)-7,7-dimethyl-5-oxo-5,6,7,8-
tetrahydro-4H-chromene-3-carboxylic Acid Ethyl Ester, 4d
Yield 60%; white solid powder; mp 162–164 ꢁC; Rf value in TLC 0.70 (neat
chloroform); IR (KBr) (nmax, cmꢂ1): 3400, 3300 (N-H), 1680, 1640 (C O), 1630,
=
=
1520 (C C stretching of phenyl) 1360 (C-N stretching), 1270, 1190 (C-O stretching);
1H NMR d (in ppm): 7.35 (d, J ¼ 7.70 Hz, ArH, 1H), 7.20 (d, J ¼ 8.20 Hz, ArH, 1H),
7.18–7.10 (m, ArH, 1H), 7.10–7.02 (m, ArH, 1H), 6.25 (br s, NH2, 2H), 5.00 (s, C4-
H, 1H), 4.05 (q, J ¼ 7.40 Hz, -CH2CH3, 2H), 2.45 (s, methylene protons at C-6, 2H),
2.25 (d, J ¼ 13.80 Hz, C8-H, 1Hax), 2.15 (d, J ¼ 13.80 Hz, C8-H, 1Heq), 1.15 (t,
J ¼ 7.40 Hz, -CH2CH3, 3H), 1.10 (s, CH3 at C-7, 3H), 0.950 (s, another CH3 at
C-7, 3H); MS: m=z 375.15 (Mþ). Anal. calcd. for C20H22NO4Cl: C, 64.0; H, 5.87;
N, 3.73. Found: C, 63.84; H, 5.92; N, 3.84.
2-Amino-4-(4-methylphenyl)-5-oxo-5,6,7,8-tetrahydro-4H-
chromene-3-carboxylic Acid Ethyl Ester, 4e
Yield 55%; white crystalline solid; mp 168–169 ꢁC; Rf value in TLC 0.75 (neat
chloroform); IR (KBr) (nmax, cmꢂ1): 3400, 3000 (N-H), 1680, 1640 (C O), 1520
=
=
(C C stretching of phenyl), 1360 (C-N stretching), 1280, 1210 (C-O stretching);

2826
M. G. AHMED ET AL.
1H NMR d (in ppm): 7.15 (d, J ¼ 8.50 Hz, ArH, 2H), 7.00 (d, J ¼ 8.0, ArH, 2H), 6.15
(br s, NH2, 2H), 4.70 (s, C4-H, 1H), 4.00 (q, J ¼ 7.80 Hz, -CH2CH3, 2H), 2.60–2.50
(m, methylene protons at C-6, 2H), 2.40–2.30 (m, methylene protons at C-8, 2H),
2.30 (s, ArCH3, 3H), 2.10–1.90 (m, methylene protons at C-7, 2H), 1.15 (t,
J ¼ 7.80 Hz, -CH2CH3, 3H) ; MS: m=z 327.20 (Mþ). Anal. calcd. for C19H21NO4:
C, 69.72; H, 6.42; N, 4.28. Found: C, 69.62; H, 6.50; N, 4.15.
2-Amino-4-(2-methoxyphenyl)-5-oxo-5,6,7,8-tetrahydro-4H-
chromene-3-carboxylic Acid Ethyl Ester, 4f
Yield 50%; white crystalline solid; mp 208–210 ꢁC; Rf value in TLC 0.72 (neat
chloroform); IR (KBr) (nmax, cmꢂ1): 3350, 3200 (N-H), 1710, 1640 (C O), 1590,
=
=
1505 (C C stretching of phenyl), 1390 (C-N stretching), 1280, 1210 (C-O stretching);
1H NMR d (in ppm): 7.35 (d, J ¼ 7.70 Hz, ArH, 1H), 7.18–7.10 (m, ArH, 1H),
6.88–6.80 (m, ArH, 1H), 6.75 (d, J ¼ 8.60 Hz, ArH, 1H), 6.15 (br s, NH2, 2H),
4.80 (s, C4-H, 1H), 4.05 (q, J ¼ 7.80 Hz, -CH2CH3, 2H), 3.80 (s, OCH3, 3H),
2.58–2.50 (m, methylene protons at C-6, 2H), 2.35–2.27 (m, methylene protons at
C-8, 2H), 2.05–1.85 (m, methylene protons at C-7, 2H), 1.15 (t, J ¼ 7.80 Hz,
-CH2CH3, 3H); MS: m=z 343.20 (Mþ). Anal. calcd. for C19H21NO5: C, 66.47; H,
6.12; N, 4.08. Found: C, 65.84; H, 6.11; N, 4.15.
2-Amino-4-(2-chlorophenyl)-5-oxo-5,6,7,8-tetrahydro-4H-
chromene-3-carboxylic Acid Ethyl Ester, 4g
Yield 60%; white crystalline solid; mp 222–224 ꢁC; Rf value in TLC 0.64 (neat
chloroform); IR (KBr) (nmax, cmꢂ1): 3400, 3000 (N-H), 1680, 1640 (C O), 1610,
=
=
1500 (C C stretching of phenyl), 1360 (C-N stretching), 1250, 1210 (C-O stretching);
1H NMR d (in ppm): 7.35 (d, J ¼ 7.70 Hz, ArH, 1H), 7.20 (d, J ¼ 7.70 Hz, ArH, 1H),
7.15–7.10 (m, ArH, 1H), 7.10–7.0 (m, ArH, 1H), 6.25 (br s, NH2, 2H), 5.00 (s, C4-H,
1H), 4.00 (q, J ¼ 7.80 Hz, -CH2CH3, 2H), 2.65–2.50 (m, methylene protons at C-6,
2H), 2.35–2.28 (m, methylene protons at C-8, 2H), 2.10–1.90 (m, methylene protons
at C-8, 2H), 1.15 (t, J ¼ 7.80 Hz, -CH2CH3, 3H). MS: m=z 347.14 (Mþ). Anal. calcd.
for C18H18NO4Cl: C, 62.16; H, 5.18; N, 4.03. Found: C, 62.19; H, 5.19; N, 4.07.
ACKNOWLEDGMENT
We are pleased to acknowledge Teruo Shinmyozu, Institute for Materials
Chemistry and Engineering, Kyushu University, Japan, for the mass spectrum,
NMR, and elemental analyses.
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