Aqueous extract of Balanites roxburghii fruit: A green dispersant for C-C bond formation

Article abstract of DOI:10.1039/c4ra04387a

An aqueous biosurfactant solution, a biobased green acidic catalyst for Knoevenagel condensation of 1,3-indanedione with aryl aldehydes and tandem Knoevenagel-Michael reaction of 3-methyl-1-phenylpyrazole with aryl aldehydes, has been reported for the fir

Full text of DOI:10.1039/c4ra04387a

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Aqueous extract of Balanites roxburghii fruit: a
green dispersant for C–C bond formation
Cite this: RSC Adv., 2014, 4, 31177
*
Madhuri Barge and Rajashri Salunkhe
An aqueous biosurfactant solution, a biobased green acidic catalyst for Knoevenagel condensation of 1,3-
indanedione with aryl aldehydes and tandem Knoevenagel–Michael reaction of 3-methyl-1-phenylpyrazole
with aryl aldehydes, has been reported for the first time. The synthetic pathway complies with several key
requirements of green chemistry principles such as the use of renewable feedstock, aqueous conditions,
waste prevention, atom economy along with the biodegradable and recyclable catalyst. Thus the
presented protocol offers an attractive option because of its versatility, ecological safety, environmental
acceptance and sustainability.
Received 11th May 2014
Accepted 3rd July 2014
DOI: 10.1039/c4ra04387a
www.rsc.org/advances
surfactants.8 Also, due to the high natural abundance their
production is potentially less expensive.
Introduction
Biosurfactants (surface active agents) are microbial amphi-
philic polymers obtained from plants, animals or microorgan-
isms. They form part of an emergent tool with a great potential
for industrial applications including the use in enhanced oil
recovery, crude oil drilling, lubricants, health care and food
processing industry.9 Also full evaluations of the potential of
these natural dispersants in cosmetic and soap formulations,
foods and dermal or transdermal drug delivery systems are
developing at an incredible rate.10 Notably, despite their diverse
applications in industry and environmental biotechnology,
their potential in accelerating the organic transformations has
not been evolved till date. Therefore the aim of present work is
to explore the synthetic utility of natural sugar-based surfactant
in organic transformations. The catalytic medium is sourced
from the aqueous extract of Balanites roxburghii fruit. From
literature records it is well known that the Balanites roxburghii
fruit locally known as Hingota in India is a wild plant species
traditionally used as emetic, anthelmintic, anti-fungal, and
purgative, in whooping cough, skin diseases and snake bite.
Phytochemical study showed the presence of alkaloids, avo-
noids, tannins, phenolic compounds and saponins.11 In addi-
tion to this, aqueous fruit extract exhibits acidic pH (ca. 4.86). In
view of this data and in continuation of our ongoing research in
the development of green synthetic routes,13 we thought this
amazing medium may serve as a better alternative to chemical
surfactants and also to harmful corrosive acids.
Recently energy efficient technologies eliminating waste
production, toxic and hazardous solvents and reagents as well
as employing renewable raw materials are experiencing a
profound challenge to meet sustainability criteria.1 In addition
the environmental risks posed by the volatile organic solvents
have become a major concern. The reason is that the organic
transformations employ higher consumption of solvents than
the reagents and the employed solvents are difficult to recycle.2
For the process to be in line with the green chemistry principles,
the rst task is to replace the volatile organic solvents with
green ones.
An ideal solvent that meets all the goals of function,
performance, economy and greenness is water, which has wit-
nessed increasing popularity due to being inexpensive, readily
available, non-inammable, non-toxic, safe and environmen-
tally benign.3 However, organic reactions in water are oen
limited in scope due to the scarce solubility of many of the
organic compounds. A possible new way to improve the solu-
bility of organic substrates is the use of amphiphiles such as
surfactants,4 hydrotropes5 and phase transfer catalysts.6
Nowadays biosynthetic processes involving biobased
solvents or catalysts have received much attention as a viable
alternative for the development of green methodologies for
organic synthesis.7 In this regard, biosurfactants or natural
dispersants as a part of the chemical process offer an excellent
alternative to volatile organic solvents in being more environ-
mental friendly technologies due to their low toxicity, ease of
biodegradability, ability to act as catalyst, non-ammability and
non-corrosive properties as compared to petroleum-based
Results and discussion
Initially, we focused our attention to prepare dispersant solu-
tion from Balanites roxburghii fruit. For this purpose mesocarp
of a dried fruit was crushed to get powder which weighted about
3–4 g. The powder (1 g) was soaked in distilled water (100 mL)
Department of Chemistry, Shivaji University, Kolhapur, 416004, Maharashtra, India.
E-mail: rsschem1@gmail.com; Fax: +91 231 2692333; Tel: +91 231 2609240
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for 12 hours. The resultant material was then macerated and addition of acid or base could not change the pH of catalytic
ltered to give wine red coloured solution. medium conrming the buffering property of medium. Buff-
The next task was to optimise different reaction parameters ering action of the catalytic solution is accounted on the basis of
for Knoevenagel reaction. Knoevenagel products i.e. 2-arylide- structure of one of the saponins12 (Fig. 1) present in fruit extract.
neindane-1,3-dione scaffolds obtained from 1,3-indanedione Saponin is an amphiphilic molecule in which sugar is linked to
and aryl aldehydes are industrially important precursors sterol non-polar group. As we know sugar part acts as a buffer
because they are used as intermediates for the synthesis of and thus change in concentration by dilution with water or by
different bio-active molecules.14 As well as they own propitious addition of acid or base didn't affect the catalytic property of
pharmacological activities such as anticoagulants15 and cyto- biosurfactant solution.
toxics.16 Only sporadic reports are available for the synthesis of
these derivatives. detailed literature survey about the activity due to saponins offered synergistic effect and reaction
Thus acidic nature of aqueous extract as well as surface
A
synthesis of these derivatives revealed that most of the methods proceeded rapidly within short time. To compare the catalytic
employed operated under reux conditions using various cata- activity of natural surfactant with chemical surfactant, we also
lysts including acids or bases such as acetic acid, concentrated carried out the model reaction using synthetic surfactants
H2SO4,15 gaseous HCl and p-TSA,17 piperidine.18 Ren et al. (Table 1, entry 3 and 4). Natural surfactant was found to be
reported solvent-free route by grinding method in presence of excellent alternative to the chemical surfactants with respect to
silica gel and MgO as catalysts at ambient temperature.19 time as well as yield of the product. In addition biosurfactant is
Recently, Yang et al. reported catalyst-free synthesis of 2-aryli- a recyclable buffer system which furnished the constant yield of
deneindane-1,3-diones in reuxing water but the process is very product for several runs (Table 1, entry 5) indicating its versatile
tedious and lengthy.20 Thus, the generality of the existing reusability which is seldom possible for chemical surfactants. A
reports is somewhat visited by the severe reaction conditions controlled reaction conducted under identical conditions and
and the catalysts and solvents used are not acceptable in the devoid of biosurfactant only in water could not furnish the
context of green synthesis. To defeat these circumstances we corresponding product, despite the prolonged reaction times
employed a simple and efficient micellar approach which led to indicates role of biosurfactant is decisive (Table 1, entry 6).
the development of new, rapid and robust route towards
focused libraries.
Aer the optimization of concentration, a series of struc-
turally diverse aryl aldehydes were treated with 1,3-indanedione
To optimize the reaction conditions, a round bottom ask in diluted dispersant solution at ambient temperature (Table 2).
was charged with 1,3-indanedione 1 (1 mmol) and 2-nitro- The reactions proceeded at room temperature within 5 to 20
benzaldehyde 2h (1 mmol). To this, aqueous fruit extract (5 mL) minutes affording the desired products in excellent yields. The
was added and stirred the mixture at room temperature. On the aryl aldehydes bearing electron-donating as well as electron-
completion of reaction as monitored by TLC, the product withdrawing groups underwent reactions successfully. The
separated out by simple ltration which on sufficient washing method is also suitable for the sterically hindered 1-naph-
with water and ethanol afforded the corresponding product of thaldehyde (Table 2, entries 10). In addition, heteroaromatic
high purity.
aldehydes such as furfuraldehyde and thiophene-2-aldehyde
To check the effect of dilution on the yield of product, the (Table 2, entries 14 and 15) reacted efficiently furnishing
model reaction was carried out with various concentrations of anticipated products in good yields. In all the cases 2-arylide-
dispersant solution. Initially prepared wine coloured solution neindane-1,3-diones were the sole products and no anomalies
was diluted with distilled water till to get a clear solution. It was were noted. Pure products obtained by washing with water and
surprising to note that there was no effect on the yield of hot ethanol were characterised by their physical constants and
product even with the much diluted clear solution (Table 1, spectral techniques.
entry 1 and 2).
Inspired by these tempting results obtained for Knoevenagel
To understand this effect, pH of each solution was measured condensation at ambient temperature, we extended same
and amazingly it was observed that pH remained constant for protocol for Knoevenagel–Michael reaction of aryl aldehydes
each diluted solution which indicated that the aqueous extract and 3-methyl-1-phenyl-5-pyrazolone to yield 4,40-(aryl-
of Balanites roxburghii fruit worked like buffer. Furthermore, methylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ols). This is
Table 1 Optimization of reaction parametersa
Entry
Catalyst
Time (min)
Yieldb (%)
1
2
3
4
5
6
Wine red coloured surfactant solution (5 mL)
Diluted colourless surfactant solution (5 mL)
SDS (10 mol%)
Sodium stearate (10 mol%)
Diluted colourless surfactant solution (h run)
Distilled water (5 mL)
5
5
18
25
5
94
94
86
79
94
—
6 h
a
b
Reaction conditions: 1,3-indanedione (1 mmol), 2-nitrobenzaldehyde (1 mmol), rt. Isolated yields.
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Fig. 1 Structure of saponin.
because pyrazolone nucleus is one of the most omnipresent a wide range of pharmacological activities such as gastric
heterocyclic structures found in numerous bioactive molecules secretion stimulatory,25 antidepressant,26 antibacterial27 and
with predominant properties such as antitumor,21 selective antilarial agents.28 Also, they are extensively applied as fungi-
COX-2 inhibitory22 and cytokine inhibitors.23 They found many cides, pesticides, insecticides and dyestuffs.29
applications as extractant for metal ions and ligands.24 2,4-
Synthetic route to prepare 4,40-(arylmethylene)bis(3-methyl-
Dihydro-3H-pyrazol-3-one derivatives including 4,40-(aryl- 1-phenyl-1H-pyrazol-5-ols) generally involves the tandem
methylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ols) also display Knoevenagel–Michael reaction of aryl aldehydes with two
Table 2 Synthesis of 2-arylideneindane-1,3-diones catalysed by natural dispersant
Sr. no.
Aldehyde 2(a–r)
Producta 3(a–r)
Time (min)
Yieldb (%)
mp [Lit.]c (ꢀC)
1
2
3
4
5
6
7
8
Ph
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
3q
3r
5
15
20
5
93
92
89
92
90
88
90
94
94
83
88
93
92
90
94
92
90
93
150 [152–153]15
150 [150–151]19
155 [156–157]19
180 [180–182]20
170 [170]18
4-Me-C6H4
4-OMe-C6H4
4-Cl-C6H4
4-F-C6H4
5
2-OH-C6H4
4-OH-C6H4
2-NO2-C6H4
4-NO2-C6H4
1-Naphthyl
4-N(Me)2-C6H4
4-OH, 3-OMe-C6H3
3,4,5-(OMe)3-C6H2
Furyl-2-yl
12
10
5
17
10
20
15
18
5
5
5
5
5
194 [193–195]20
241 [241–243]20
190 [192–194]20
232 [234–236]20
172 [174–176]15
178 [180]18
9
10
11
12
13
14
15
16
17
18
218–220
185 [185]18
210 [209–211]20
178–180
Thiophene-2-yl
2-CHO-C6H4
4-Br-C6H4
218–220
173–175
238–240
4-CN-C6H4
a
Representative products were characterized by IR, 1H NMR, 13C NMR and mass spectroscopy as well as elemental analysis technique. b Isolated
yields. c Literature values in parenthesis.
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equivalents of 5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one. micelle to catalyse the reaction can be explained as shown in
Several methods and catalysts have been reported in literature Fig. 2(a). As the impact of micellar solution, hydrophobic
to synthesize these derivatives including microwave irradia- reactants i.e. pyrazolone 4 and aldehyde 5 get pushed away from
tion,30 triethylbenzylammonium chloride (TEBA),31 sodium water molecules towards the hydrophobic core of micelle
dodecyl sulphate,32 electrolysis,33 cerium(IV) ammonium leading to the effective collisions and water formed by
nitrate,34 silica bonded S-sulfonic acid,35 cellulose sulphuric condensations is repelled out to give corresponding Knoeve-
acid,36 silica sulfuric acid,37 silica bonded ionic liquid38 and 1,3- nagel product 7 which was further reacted with another mole-
disulfonic acid imidazolium tetrachloroaluminate {[Dsim] cule of pyrazolone with shiing of equilibrium towards
AlCl4}.39 Although diverse approaches towards the synthesis of formation of desired product 6 with excellent yield. As the
these derivatives have been developed, use of biosurfactant is impact of micellar solution reaction mixture turned turbid due
the most elegant strategy.
to the formation of colloidal aggregates which was conrmed
The condensation reactions were carried out in 5 mL on the basis of optical microscopy (Fig. 2(b)).
aqueous extract of fruit at 60 ꢀC in a preheated oil bath using a
series of structurally diverse aryl aldehydes with 3-methyl-1-
phenyl-5-pyrazolone (Table 3). Initially Knoevenagel condensa-
tion proceeded rapidly within 2 minutes to furnish 1 : 1 prod-
ucts i.e. orange coloured arylidenepyrazolones which were
converted to nal white products through Michael step within
15–60 minutes. On the completion of reactions as monitored by
TLC, the reaction mixtures were ltered to isolate products and
puried by washing with water and hot ethanol. In IR spectrum
of all the compounds characteristic broad absorption in the
region 2500–2600 cmꢁ1 was noticed for the H-bonded enolic
–OH and carbonyl absorption was absent indicating that the
pyrazolonyl group in all compounds exists in enol form.40
Since the blank reaction only in water could not give the
corresponding products even aer the long reaction time, the
exceptionally higher catalytic activity of biosurfactant can be
Fig. 2 (a) Mechanistic picture of bispyrazolone formation. (b) Optical
related to its ability to form micelles in water. The role of micrograph of reaction mixture.
Table 3 Tandem Knoevenagel–Michael synthesis catalysed by biosurfactant
Sr. no.
Aldehyde 5(a–m)
Producta 6(a–m)
Time (min)
Yieldb (%)
mp [Lit.]c (ꢀC)
1
2
3
4
5
6
7
8
Ph
6a
6b
6c
6d
6e
6f
6g
6h
6i
15
20
30
20
20
25
25
25
30
50
25
35
60
90
93
90
92
90
88
85
83
89
86
89
90
87
170–171 [169–171]32
200–202 [203]32
4-Me-C6H4
4-OMe-C6H4
2-Cl-C6H4
4-Cl-C6H4
4-Br-C6H4
4-F-C6H4
4-NO2-C6H4
2-NO2-C6H4
3-NO2-C6H4
Thiophene-2-yl
2-CHO-C6H4
1-Naphthyl
148–150 [148]40b
235–236 [235–237]32
215–217 [214–217]39
215–217 [215]40b
180–182 [182]40b
218–220 [218–220]32
220–222 [221–222]32
151–153 [151–153]32
187–189 [189–190]39
247–250
9
10
11
12
13
6j
6k
6l
6m
208–210
a
Representative products were characterized by IR, 1H NMR, 13C NMR spectroscopy and elemental analysis technique. b Isolated yields. c Literature
values in parenthesis.
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spectrometry as well as by elemental analysis. The physical and
spectroscopic data are in consistent with the proposed struc-
tures and are in harmony with the literature values.
Conclusion
In summary, we report a straightforward bioorganic approach
for C–C bond construction via Knoevenagel condensation and
tandem Knoevenagel–Michael reaction which represents a
highly efficient and environmental benign system. Apart from
this simplicity of product separation and effortless reusability of
catalyst are the signicant advantages of this protocol. This new
acidic dispersant should thereby provide attractive alternative
to the harmful corrosive acids. However in true sense, we think
that biosurfactant doesn't offer only a synergistic effect of acidic
nature and surface activity but might be combination of many
other factors. Hence to have a good contribution in innovation
of green chemistry, we will lengthen our research to have
more exposure to natural dispersant mediated organic
transformations.
General procedure for synthesis of 4,40-(arylmethylene)-bis-
(3-methyl-1-phenyl-1H-pyrazol-5-ol)s
In a 100 mL round bottom ask 3-methyl-l-phenyl-5-pyrazolone
(2 mmol) and aldehyde (1 mmol) were placed in biosurfactant
ꢀ
solution (5 mL) and stirred at 60 C temperature in preheated
oil bath till the completion of reaction as indicated by TLC (pet.
ether : ethyl acetate, 8 : 2). The solid products were separated by
simple ltration and puried by washing with water and hot
ethanol. Representative compounds were conrmed by physical
constants and characterized by spectral analysis.
Spectral data of representative compounds
2-(4-Chlorobenzylidene)-2H-indene-1,3-dione (Table 2, entry
3d): white solid; mp 180 ꢀC; IR (KBr): nmax/cmꢁ1 ¼ 1726 and
1690 (CO), 1580, 831, 736; 1H NMR (300 MHz, CDCl3): d ¼ 7.49–
7.52 (d, 2H), 7.84–7.88 (m, 3H), 8.02–8.06 (m, 2H), 8.44–8.46 (d,
2H) ppm; 13C NMR (75 MHz, CDCl3): d ¼ 123.4, 123.4, 129.1,
129.5, 131.7, 135.3, 135.5, 139.5, 140.5, 143.0, 145.1, 189.1 (CO),
190.3 (CO) ppm; elemental analysis: requires: C, 71.52; H, 3.38;
O, 11.91% (C16H9O2Cl) found: C, 71.49; H, 3.40; O, 11.97%.
Experimental
Solvents and reagents were commercially sourced from Sigma
Aldrich and used without further purication. Melting points
were determined in an open capillary and are uncorrected.
Infrared spectra were measured with a Perkin Elmer FT-IR
spectrophotometer. The samples were examined as KBr discs
1
ꢂ5% w/w. H NMR and 13C NMR spectra were recorded on a
Bruker AC (300 MHz for 1H NMR and 75 MHz for 13C NMR)
spectrometer using CDCl3 and DMSO-d6 as solvents. Chemical
shis are expressed in d parts per million (ppm) values with
tetramethylsilane (TMS) as the internal reference and coupling
constants are expressed in Hertz (Hz). Mass spectra were
recorded on Shimadzu QP2010 GCMS. Elemental analysis was
carried out using Euro EA 3000 Vectro model. Optical micro-
graph was taken using ordinary light microscope (Leica DM
2000) under 100ꢃ magnications.
2-(4-Hydroxy, 3-methoxybenzylidene)-2H-indene-1,3-dione
ꢀ
(Table 2, entry 3l): yellow solid; mp 218–220 C; IR (KBr): nmax
/
cmꢁ1 ¼ 3453 (OH), 1715 and 1672 (CO), 998, 740 cmꢁ1; 1H NMR
(300 MHz, CDCl3): d ¼ 4.15 (s, 3H), 6.27 (s, 1H), 7.00–7.03 (d,
1H), 7.60–7.64 (dd, 1H), 7.78–7.83 (m, 3H), 7.97–8.01 (m, 2H),
9.04 (d, 1H) ppm; 13C NMR (75 MHz, CDCl3): d ¼ 56.1, 114.5,
115.1, 122.9, 123.1, 126.1, 126.6, 132.2, 134.6, 134.8, 140.0,
142.4, 146.3, 147.7, 151.2, 189.6 (CO), 190.3 (CO) ppm;
elemental analysis: requires: C, 72.85; H, 4.32; O, 22.83%
(C16H10O3) found: C, 72.80; H, 4.38; O, 22.84%.
2-((Thiophen-2-yl)methylene)-2H-indane-1,3-dione (Table 2,
Preparation of aqueous extract from plant material
entry 3o): yellow solid; mp 178–180 C; IR (KBr): nmax/cmꢁ1
¼
ꢀ
Dried fruits of Balanites roxburghii plant were purchased from
local market and authenticated by the Department of Botany,
Shivaji University, Kolhapur, India. The mesocarp of a fruit was
crushed to get powder weighted about 3–4 g. 1 g powder was
soaked in 100 mL of distilled water for 12 hours and ltered to
get wine red coloured solution. This concentrated solution was
diluted by distilled water till to get colourless solution. Disper-
1
1724 and 1684 (CO), 1585, 811, 726 cmꢁ1; H NMR (300 MHz,
CDCl3): d ¼ 7.25–7.27 (m, 1H), 7.79–7.83 (m, 1H), 7.87–7.88 (d,
1H), 7.98–8.06 (m, 3H), 8.10–8.11 (d, 1H) ppm; 13C NMR (75
MHz, CDCl3): d ¼ 123.0, 123.1, 124.9, 128.5, 134.7, 134.9, 136.0,
137.5, 137.9, 140.4, 141.3, 142.1, 188.9 (CO), 189.7 (CO) ppm;
elemental analysis: requires: C, 69.98; H, 3.36; O, 13.32%
(C14H8O2S) found: C, 69.96; H, 3.40; O, 13.35%.
ꢀ
sant solution was stored below 5 C and found to be stable for
2-((1,3-Dioxo-1H-inden-2(3H)-ylidene)methyl)benzaldehyde
several months.
ꢀ
(Table 2, entry 3p): white solid; mp 218–220 C; IR (KBr): nmax
/
cmꢁ1 ¼ 1723, 1710 and 1691 (CO), 1589, 805, 733 cmꢁ1; 1H NMR
(300 MHz, CDCl3): d ¼ 7.69–7.74 (t, 1H), 7.85–7.90 (m, 2H), 7.94–
7.98 (m, 1H), 8.03–8.11 (m, 3H), 8.67–8.69 (d, 1H), 9.03 (s, 1H),
General procedure for synthesis of 2-arylideneindane-1,3-
diones
A mixture of 1,3-indanedione (1 mmol) and aldehyde (1 mmol) 10.16 (s, 1H) ppm; 13C NMR (75 MHz, CDCl3): d ¼ 123.5, 123.6,
in biosurfactant (5 mL) was stirred at ambient temperature till 129.4, 130.6, 132.2, 133.8, 135.3, 135.4, 135.8, 136.9, 139.0,
the completion of reaction as indicated by TLC (pet. ether- 140.2, 142.6, 144.5, 188.4 (CO), 189.1 (CO), 190.8 (CO) ppm;
: ethyl acetate, 7 : 3). The solid products were separated by mass (EI): m/z ¼ 262; elemental analysis: requires: C, 77.85; H,
adding 50 mL water followed by simple ltration. The pure 3.84; O, 18.30% (C17H10O3) found: C, 77.88; H, 3.80; O, 18.31%.
products were obtained by washing with water and hot ethanol.
2-(4-Bromobenzylidene)-2H-indene-1, 3-dione (Table 2, entry
The identity of representative compounds was ascertained on 3q): yellow solid; mp 173–175 C; IR (KBr): nmax/cmꢁ1 ¼ 1725
ꢀ
the basis of IR, 1H NMR, 13C NMR spectroscopy and mass and 1689 (CO), 1578, 991, 736 cmꢁ1; 1H NMR (300 MHz, CDCl3):
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d ¼ 7.66–7.88 (d, 2H), 7.82–7.88 (m, 3H), 8.02–8.05 (m, 2H), (s, 1H, CH), 7.33–7.42 (m, 17H, ArH) ppm; 13C NMR (75 MHz,
8.35–8.38 (d, 2H) ppm; 13C NMR (75 MHz, CDCl3): d ¼ 123.4, DMSO-d6): d ¼ 12.2, 31.4, 106.0, 120.5, 123.7, 125.4, 125.5,
123.5, 128.3, 129.6, 131.9, 132.1, 135.2, 135.3, 135.4, 140.1, 126.1, 126.2, 127.4, 129.0, 129.1, 129.1, 131.2, 134.1, 137.0,
142.6, 145.1, 188.7 (CO), 189.6 (CO) ppm; elemental analysis: 137.7, 146.1, 158.8 ppm; elemental analysis: requires: C, 76.52;
require: C, 61.37; H, 2.90; O, 10.22% (C16H9O2Br) found: C, H, 5.39; O, 6.58% (C31H26N4O2) found: C, 76.55; H, 5.32; O,
61.41; H, 2.91; O, 10.19%.
6.60%.
2-(4-Cyanobenzylidene)-2H-indene-1, 3-dione (Table 2, entry
3r): yellow solid; mp 238–240 ꢀC; IR (KBr): nmax/cmꢁ1 ¼ 2227
Acknowledgements
1
(CN), 1727 and 1689 (CO), 1589, 989, 733 cmꢁ1; H NMR (300
MHz, CDCl3): d ¼ 7.80–7.92 (m, 5H), 8.05–8.08 (q, 2H), 8.51–8.54 We gratefully acknowledged the nancial support from the
(d, 2H) ppm; 13C NMR (75 MHz, CDCl3): d ¼ 115.5, 117.9, 123.6, Department of Science Technology and University Grants
123.7, 131.8, 132.2, 133.7, 135.6, 135.7, 136.6, 140.2, 142.6, Commission for FIST and SAP respectively. One of the authors
143.2, 188.2 (CO), 188.9 (CO) ppm; mass (EI): m/z ¼ 282; Madhuri Barge thanks the Department of Science Technology,
elemental analysis: requires: C, 78.76; H, 3.50; O, 12.34% New Delhi, India for the award of PURSE fellow.
(C17H9NO2) found: C, 78.80; H, 3.52; O, 12.32%.
4,40-(Phenylmethylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-
References
ol) (Table 3, entry 6a): pale yellow solid; mp 170–172 ꢀC; IR
1
(KBr): nmax/cmꢁ1 ¼ 2620 (OH), 1615, 1489, 780 cmꢁ1; H NMR
(300 MHz, DMSO-d6): d ¼ 2.30 (s, 6H, CH3), 4.98 (s, 1H, CH),
7.12–7.16 (m, 1H, ArH), 7.21–7.25 (m, 6H, ArH), 7.38–7.42 (t, 4H,
ArH), 7.58–7.62 (d, 4H, ArH) ppm; 13C NMR (75 MHz, DMSO-d6):
d ¼ 12.0, 33.5, 121.3, 126.4, 126.5, 127.7, 128.7, 129.5, 137.4,
142.5, 146.8 ppm; elemental analysis requires: C, 74.29; H, 5.54;
O, 7.33% (C27H24 N4O2) found: C, 74.31; H, 5.50; O, 7.38%.
4,40-[(4-Chlorophenyl)methylene]bis(3-methyl-1-phenyl-1H-
pyrazol-5-ol) (Table 3, entry 6e): white solid; mp 215–217 ꢀC; IR
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1
(KBr): nmax/cmꢁ1 ¼ 2553 (OH), 1598 cmꢁ1; H NMR (300 MHz,
DMSO-d6): d ¼ 2.31 (s, 6H, CH3), 4.86 (s, 1H, CH), 7.18–7.21 (d,
6H, ArH), 7.34–7.39 (t, 4H, ArH), 7.69–7.02 (d, 4H, ArH), 13.69
(brs, 1H, OH) ppm; 13C NMR (75 MHz, CDCl3): d ¼ 11.8, 3 3.1,
120.9, 125.6, 128.2, 128.8, 129.1, 131.5, 137.6, 140.7, 145.9 ppm;
elemental analysis: requires: C, 68.86; H, 4.92; O, 6.79%
(C27H23N4O2Cl) found: C, 68.80; H, 4.94; O, 6.75%.
4,40-[(2-Thienyl)methylene]bis(3-methyl-1-phenyl-1H-pyr-
azol-5-ol) (Table 3, entry 6k): off white solid; mp 190–193 ꢀC; IR
(KBr): nmax/cmꢁ1 ¼ 2600, 1525 cmꢁ1; 1H NMR (300 MHz, DMSO-
d6): d ¼ 2.32 (s, 6H, CH3), 5.04 (s, 1H, CH), 6.74–6.75 (d, 4H,
ArH), 6.84 (s, 1H, ArH), 7.17–7.22 (t, 3H, ArH), 7.37–7.41 (t, 3H,
ArH), 13.88 (brs, 1H, OH) ppm; 13C NMR (75 MHz, CDCl3): d ¼
11.8, 30.7, 120.8, 124.0, 124.9, 125.7, 126.9, 128.9, 145.7, 147.6
ppm; elemental analysis: requires: C, 67.85; H, 5.01; O, 7.23%
(C25H22N4O2S) found: C, 67.80; H, 5.05; O, 7.27%.
´ ˆ
4,40-[(2-Formyl)methylene]bis(3-methyl-1-phenyl-1H-pyrazol-
ꢀ
5-ol) (Table 3, entry 6l): white solid; mp 247–250 C; IR (KBr):
1
nmax/cmꢁ1¼ 2552 (OH), 1688 (CO), 1598, cmꢁ1; H NMR (300
MHz, DMSO-d6): d ¼ 2.34 (s, 6H, CH3), 4.96 (s, 1H, CH), 7.15–
7.20 (m, 2H, ArH), 7.34–7.47 (m, 4H, ArH), 7.57–7.59 (d, 2H,
ArH), 7.70–7.73 (m, 6H), 9.92 (s, 1H), 13.80 (brs, 1H, OH) ppm;
13C NMR (75 MHz, CDCl3): d ¼ 11.9, 33.5, 104.7, 120.9, 125.7,
127.8, 128.5, 128.9, 129.1, 133.8, 136.5, 137.6, 143.4, 146.1, 10 (a) R. Makkar and S. Cameotra, Appl. Microbiol. Biotechnol.,
157.6, 192.6 ppm; elemental analysis: requires: C, 72.40; H,
5.21; O, 10.33% (C28H24N4O3) found: C, 72.44; H, 5.18; O,
10.37%.
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(KBr): nmax/cmꢁ1 ¼ 2585 (OH), 1608, 1544, 1497, 1402, 784 13 (a) A. Kumbhar, S. Kamble, M. Barge, G. Rashinkar and
1
cmꢁ1; H NMR (300 MHz, CDCl3): d ¼ 2.32 (s, 6H, CH3), 5.52
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