A convenient synthesis of 4-aryl-7,7-dimethyl-5-oxo- 3,4,5,6,7,8-hexahydrcoumarin under microvave irradiation without catalyst

Article abstract of DOI:10.1081/SCC-100108221

A series of hexahydrocoumarins 4 were synthesized by the reaction of aromatic aldehyde, 5,5-dimethyl-1,3-cyclohexandione and meldiums acid under microwave irradiation without catalyst. The structure of 4a was determined by x-ray analysis.

Full text of DOI:10.1081/SCC-100108221

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A CONVENIENT SYNTHESIS OF 4-
ARYL-7,7-DIMETHYL-5-OXO- 3,4,5,6,7,8-
HEXAHYDROCOUMARIN UNDER MICROWAVE
IRRADIATION WITHOUT CATALYST
Shu-jiang Tu a , Jian-Feng Zhou b , Pei-jun Cai a , Hai Wang c & Jun-cai Feng d
a Department of Chemistry , Xuzhou Normal University , Xuzhou, 221 009, P. R. China
b Department of Chemistry , Huaiyin Teachers College , Huaiyin, 223 001, P. R. China
c Department of Chemistry , Nanjing University , Nanjing, 210 093, P. R. China
d Department of Chemistry , Nanjing University , Nanjing, 210 093, P. R. China
Published online: 09 Nov 2006.
To cite this article: Shu-jiang Tu , Jian-Feng Zhou , Pei-jun Cai , Hai Wang & Jun-cai Feng (2001) A CONVENIENT
SYNTHESIS OF 4-ARYL-7,7-DIMETHYL-5-OXO- 3,4,5,6,7,8-HEXAHYDROCOUMARIN UNDER MICROWAVE IRRADIATION WITHOUT
CATALYST, Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry,
31:24, 3729-3733, DOI: 10.1081/SCC-100108221
To link to this article: http://dx.doi.org/10.1081/SCC-100108221
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SYNTHETIC COMMUNICATIONS, 31(24), 3729–3733 (2001)
A CONVENIENT SYNTHESIS OF
4-ARYL-7,7-DIMETHYL-5-OXO-
3,4,5,6,7,8-HEXAHYDROCOUMARIN
UNDER MICROWAVE IRRADIATION
WITHOUT CATALYST
Shu-jiang Tu,1 Jian-Feng Zhou,2 Pei-jun Cai,1
Hai Wang,3 and Jun-cai Feng3,
*
1Department of Chemistry, Xuzhou Normal
University, Xuzhou 221 009, P. R. China
2Department of Chemistry, Huaiyin, Teachers College,
Huaiyin 223 001, P. R. China
3Department of Chemistry, Nanjing University,
Nanjing 210 093, P. R. China
ABSTRACT
A series of hexahydrocoumarins 4 were synthesized by the
reaction of aromatic aldehyde, 5,5-dimethyl-1,3-cyclohexan-
dione and meldiums acid under microwave irradiation with-
out catalyst. The structure of 4a was determined by x-ray
analysis.
*Corresponding author.
3729
Copyright & 2001 by Marcel Dekker, Inc.
www.dekker.com

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TU ET AL.
Organic synthesis under microwave irradiation is a topic that is drawing
much recent research interest.1 In our laboratory, we have been continually
working on developing new synthetic methods for the synthesis of polyhy-
drocoumarins by taking advantage of microwave irradiation. Coumarin is
one of the most important aroma chemicals having unique characteristics.2
It is widely used in hand soaps, detergents, lotions, and perfumes. Coumarin
has significant use in the electroplating industry, mostly in the automotive
area, to provide high polished quality to chromeplated steel. Coumarin and
some of its derivatives have been tested in pharmacology for treatment of
schizophrenia,3 or of microcirculation disorders and angiopathic ulcer4 etc.
The synthesis of coumarins usually involves the method of Rasching2 disco-
vered in 1909, i.e., starting with o-cresol, or the Von Pechmann method,2 i.e.,
reaction of phenol with malic, maleic, or fumaric acids in the presence of
concentrated sulfuric acid, or from salicylaldehyde by Perkin reaction,
Knoevenagel reaction2 etc. Recently, Bogdal5 reported that the salicylalde-
hyde or its derivative react with various derivative of ethyl acetoacetate in the
presence of piperidine to give coumarins by a solvent free reaction under
microwave irradiation. Zhang et al.6 reported the synthesis of coumarin
under triphase catalysis of polystyrene-supported poly-ethylene glycol. In
our previous paper,7 we reported that aromatic aldehydes (1), dimedone (2)
and meldrums acid (3) when treated with KF-alumina in alcohols at refluxing
temperature, produce 3-aryl-3-(5,5-dimethyl-3-hydroxy-2-cyclohexene-1-
one-2-yl) propanic esters. However, when aromatic aldehydes (1), dimedone
(2) and meldrums acid (3) were treated with ethanol under microwave irra-
diation without catalyst, the product was hexahydrocoumarin (4) (scheme).
All the compounds obtained gave elemental analysis for C, H, N in good
agreement to calculated values. The structures were established on the basis
of spectroscopic data and confirmed by X-ray diffraction studies for 4a.8
EXPERIMENTAL
Melting points were determined in open capillaries and are uncor-
rected. IR spectra were recorded on a Nicolet FT-IR 5DX instrument.
Scheme.

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Table 1. The Synthesis of Compound 4
Entry
Ar
Time (min)
Yield (%)
4a
4b
4c
4d
4e
p-(CH3)2NC6H4
p-ClC6H4
p-CH3OC6H4
3,4-(OCH2O)C6H3
4-HO-3-CH3OC6H3
4
3
5
5
4
66
82
68
85
75
Figure 1. X-ray crystal structure of 4a.
1H-NMR were measured on a Bruker 300 MHz spectrometer in CDCl3 with
TMS as internal standard. Elemental analyzer were determined using
Perkin-Elmer 240C elemental analyzer. X-ray diffraction were measured
on a Nonius Kapph CCD diffractometer. The reactions were carried out
with a modified commercial microwave oven (Sanle WP650D 650w) under
atmospheric pressure.
GENERAL PROCEDURE
A mixture of aromatic aldehydes 1 (5 mmol), dimetone 2 (0.70 g,
5 mmol), meldrums acid 3 (0.72 g, 5 mmol) and 5 mL of ethanol was
transferred into a dry flask connected with refluxing equipment. After
microwave irradiation for 3–5 min, the reaction mixture was cooled with
ice–water. The precipitated product was filtered and washed with ethanol.

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TU ET AL.
The crude product was collected by filtration and recrystallised from ethanol
to give compound 4a–e.
4a: M.p. 136–138ꢀC; IR (KBr, n, cmꢁ1): 1791, 1703. 1HNMR
(CDCl3): d: 0.91 (s, 3H, CH3), 1.12 (s, 3H, CH3), 2.10 (s, 2H, CH2), 2.38
(s, 2H, COCH2), 2.64 (m, 2H, OCOCH2), 2.91 (s, 6H, 2NCH3), 4.06–4.34
(m, 1H, CH), 6.50–7.15 (m, 4H, ArH) ppm. Anal. Calcd. (%) for
C19H23NO3: C, 72.81; H, 7.33; N, 4.46. Found: C, 72.90; H, 7.28; N, 4.31.
4b: M.p. 156–158ꢀC; IR (KBr, n, cmꢁ1): 1773, 1658. 1HNMR
(CDCl3): d: 0.88 (s, 3H, CH3), 0.93 (s, 3H, CH3), 2.10 (s, 2H, CH2), 2.31
(s, 2H, COCH2), 2.65–2.72 (m, 2H, OCOCH2), 4.05 (m, 1H, CH), 6.86–7.03
(m, 4H, ArH) ppm. Anal. Calcd. (%) for C17H17ClO3: C, 66.99; H, 5.62.
Found: C, 66.89; H, 5.53.
4c: M.p. 128–130ꢀC; IR (KBr, n, cmꢁ1): 1771, 1650. 1HNMR
(CDCl3): d: 1.11 (s, 3H, CH3), 1.15 (s, 3H, CH3), 2.32 (s, 2H, CH2), 2.53
(s, 2H, COCH2), 2.90–2.92 (m, 2H, OCOCH2), 3.77 (s, 3H, OCH3), 4.25–
4.27 (m, 1H, CH), 6.68–7.06 (m, 4H, ArH) ppm. Anal. Calcd. (%) for
C18H20O4: C, 71.98; H, 6.71. Found: C, 72.04; H, 6.67.
4d: M.p. 130–132ꢀC; IR (KBr, n, cmꢁ1): 1780, 1650. 1HNMR
(CDCl3): d: 1.13 (s, 3H, CH3), 1.16 (s, 3H, CH3), 2.33 (s, 2H, CH2), 2.54
(s, 2H, COCH2), 2.90–2.91 (m, 2H, OCOCH2), 4.21–4.24 (m, 1H, CH), 5.93
(s, 2H, OCH2O), 6.11–6.64 (m, 3H, ArH) ppm. Anal. Calcd. (%) for
C18H18O5: C, 68.77; H, 5.77. Found: C, 68.83; H, 5.61.
4e: M.p. 158–160ꢀC; IR (KBr, n, cmꢁ1): 1789, 1630. 1HNMR
(CDCl3): d: 1.11 (s, 3H, CH3), 1.16 (s, 3H, CH3), 2.33 (s, 2H, CH2), 2.53
(s, 2H, COCH2), 2.91–2.93 (m, 2H, OCOCH2), 3.85 (s, 3H, OCH3), 4.22–
4.25 (m, 1H, CH), 6.60–6.82 (m, 3H, ArH), 10.91 (s, 1H, OH) ppm. Anal.
Calcd. (%) for C18H20O5: C, 68.34; H, 6.37. Found: C, 68.26; H, 6.45.
REFERENCES
1. Caddick, S. Tetrahedron 1995, 51, 10403.
2. Meuly, W.C.; Boisde, P.M. In Kirk-Othmer, Encyclopedia of
Chemical Technology, Vol. 7, (Wiley-Interscience, New York), 4th ed.,
pp. 650–654.
3. Casley-Smith, J.R. U.S. Pat. 4,593,041. (Chem. Abstra. 1986, 105,
54623k).
4. Elstner, E.F.; Beuscher, N. Ger. Pat. 3,715,990. (Chem. Abstra. 1989,
111, 50435b).
5. Bogdal; Darek. ECHET98: Electron. Conf. Heterocycle Chem. (com-
puter optical disk) 1998, 383–386; (Chem. Abstra. 2000, 132, 107850y).

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3733
6. Zhang, X.-Y.; Fan, X.-S.; Qiao, R.-Z. Lizi JiaoHuan yu Xifu 1999, 15,
374. (Chem. Abstra. 2000, 132, 107851z).
7. Daqing, S.; Shujiang, T.; Zaisheng, L.; Suhui, W.; Guiyuan, D. Synth.
Commun. 1998, 28, 3291.
8. X-ray analysis of 4a: Empirical formula C23H30NO4, F.W.
384.48, T ¼ 293(2) K, monoclinic, space group P21, a ¼ 9.3639(19) A,
b ¼ 5.9740(12) A, c ¼ 15.731(3) A, a ¼ 90ꢀ, b ¼ 102.87(3)ꢀ, g ¼ 90ꢀ,
V ¼ 857.9(3) A3, Z ¼ 2, Dc ¼ 1.488 Mg/cm3, ꢀ(M0Ka) ¼ 0.71073 A,
m ¼ 0.101 mmꢁ1, F(000) ¼ 414. 3.83 < s < 27.87, R ¼ 0.0805, Rw ¼
02441. Largest diff. Peak and hole: 0.469 and ꢁ 0.235 e Aꢁ3
.
Received in the USA February 9, 2001

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