J Chem Crystallogr (2011) 41:175–179
DOI 10.1007/s10870-010-9859-7
ORIGINAL PAPER
Synthesis and Crystal Structure of 1,7-Bis(4-methoxyphenyl)-
4-(1,3-dithiolan-2-ylidene)-1,6-heptadiene-3,5-dione
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S. G. Bubbly S. B. Gudennavar D. Viswam
C. Sudarsanakumar
Received: 17 April 2010 / Accepted: 17 July 2010 / Published online: 1 August 2010
Ó Springer Science+Business Media, LLC 2010
Abstract The synthesis and crystal structure of 1,7-bis(4-
methoxyphenyl)-4-(1,3-dithiolan-2-ylidene)-1,6-heptadiene-
3,5-dione is described. This compound crystallizes in the
3,5-diones) constitute the most important active chemical
components in the herbaceous medicinal plant Curcuma
longa Linn (turmeric). Extensive work has been done to
establish the biological activities and pharmacological
actions of turmeric and its extracts. Curcumin (difer-
uloylmethane) has been shown to have anti-inflammatory,
antioxidant, anticarcinogenic, antimutagenic, anticoagulant,
antibacterial, antifungal properties, etc. [1–7]. Natural and
synthetic curcuminoid analogues are reported to possess
antitumour, antioxidant, antimutagenic and anti-inflamma-
tory activities [8–13]. The synthetic curcuminoid analogue
1,7-bis(4-methoxyphenyl)-1,6-heptadiene-3,5-dione which
also shows antitumour activity is closely related to the title
compound except for the cyclic ketenedithioacetal substi-
tution at the C(4) position [14]. The structure investigation of
the title compound gains considerable attention in this con-
text (Fig. 1).
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space group P21 with unit cell parameters a = 14.207 A,
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b = 7.752(1) A, c = 19.473(1) A, b = 91.00(3)°, with two
molecules in the asymmetric unit. The ketenedithioacetal
functionality present between the carbonyl groups prevents
the possibility of keto-enol tautomerization in this compound.
Thecinnamoylgroupsareorganizedparalleltoeachother due
tothepush–pullnatureoftheketenedithioacetalfunctionality.
Keywords Crystal structure ꢀ 1,6-Heptadiene-3,5-dione ꢀ
Curcumin analogue ꢀ Ketenedithioacetal ꢀ X-ray diffraction
Introduction
The title compound 1,7-bis(4-methoxyphenyl)-4-(1,3-di-
thiolan-2-ylidene)-1,6-heptadiene-3,5-dione is a derivative
of curcumin, 1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-
heptadiene-3,5-dione, the main yellow bioactive component
of turmeric, which is widely used as a spice in traditional
cooking in Asia. Curcuminoids (1,7-diaryl-1,6-heptadiene-
Curcumin and its analogues usually have a linear struc-
ture and they exist in the completely enolized form, with the
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substituted cinnamoyl groups far apart (5.015 A in curcu-
min), as shown by their crystal structures [15, 16]. The
crystal studies on 1,6-hexadiene-3,5-dione and 1,6-hept-
adiene-3,5-dione, having unsubstituted methylene groups
show linear structures as should be expected due to the keto-
enol tautomerisation [15–19]. The extended conjugation
resulting from the enolization contributes to the stability of
their linear structure. Crystal structures of 3-aryl-substituted
2,4-pentanedione derivatives are found to exist in enol forms
[20, 21] whereas cyclic ketenedithioacetal substitution pre-
vents enolization in 3-(1,3-dithiolan-2-ylidene) pentane-2,
4-dione [22]. In bis (cinnamoyl) ketenedithioacetal, the
ketenedithioacetal functionality present between the car-
bonyl groups prevents the possibility of keto-enol tauto-
merization observed in enolizable 1,3-carbonyl compounds
[23–26]. The crystal structure of the title compound shows
S. G. Bubbly (&) ꢀ S. B. Gudennavar
Department of Physics, Christ University, Hosur Road,
Bangalore 560 029, Karnataka, India
e-mail: bubblysg@rediffmail.com;
D. Viswam
Department of Chemistry, Sree Narayana College,
Cherthala 688 524, Kerala, India
C. Sudarsanakumar
School of Pure and Applied Physics, Mahatma Gandhi
University, Kottayam 686 560, Kerala, India
123
Bubbly
