An efficient and modified biginelli-type synthesis of 3,4-dihydro-1H-indeno[1,2-d]pyrimidine-2,5-dione using phosphorous pentoxide

Article abstract of DOI:10.1080/00397911.2014.947652

A simple, clean and convenient one-pot method has been developed for the synthesis of 4-phenyl-3,4-dihydro-1H-indeno[1,2-d]pyrimidine-2,5-dione and 4-phenyl-2-thioxo-1,2,3,4-tetrahydro-5H-indeno[1,2-d]pyrimidine-5-one by multicomponent condensation of 1,3-indanedione, aromatic aldehydes and urea/thiourea using phosphorus pentoxide in ethanol under reflux conditions. The simple workup procedure and moderate to good yields within short time are some important features of this protocol. The synthesized compounds have been interpreted on the basis of their spectroscopic data.

Full text of DOI:10.1080/00397911.2014.947652

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An Efficient and Modified Biginelli Type Synthesis of
3, 4-dihydro-1H-indeno [1, 2-d] pyrimidine-2, 5-dione
Using Phosphorous Pentoxide
Poojali P. Warekara, Govind B. Kolekarb, Madhukar B. Deshmukhb & Prashant V. Anbhuleb
a Department of Agrochemicals and Pest Management, Shivaji University, Kolhapur, M.S.,
India
b Medicinal Chemistry Research Lab., Department of Chemistry, Shivaji University, Kolhapur,
M.S., India
Accepted author version posted online: 10 Sep 2014.
To cite this article: Poojali P. Warekar, Govind B. Kolekar, Madhukar B. Deshmukh & Prashant V. Anbhule (2014): An
Efficient and Modified Biginelli Type Synthesis of 3, 4-dihydro-1H-indeno [1, 2-d] pyrimidine-2, 5-dione Using Phosphorous
Pentoxide, Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, DOI:
10.1080/00397911.2014.947652
To link to this article: http://dx.doi.org/10.1080/00397911.2014.947652
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An Efficient and Modified Biginelli type Synthesis of 3, 4-dihydro-1H-indeno [1, 2-
d] pyrimidine-2, 5-dione Using Phosphorous Pentoxide.
Poojali P. Warekar1, Govind B. Kolekar2, Madhukar B. Deshmukh2, Prashant V.
Anbhule2
1Department of Agrochemicals and Pest Management, Shivaji University, Kolhapur,
M.S., India 2Medicinal Chemistry Research Lab., Department of Chemistry, Shivaji
University, Kolhapur, M.S., India
Corresponding author Prashant V.Anbhule: Medicinal Chemistry Research Lab.,
Department of Chemistry, Shivaji University, Kolhapur, 416004, M.S., India E-mail:
pvanbhule2011@gmail.com
Abstract
A simple, clean and convenient one pot method has been developed for the synthesis of
4-phenyl-3,4-dihydro-1H-indeno[1,2-d] pyrimidine-2,5-dione and 4-phenyl-2-thioxo-
1,2,3,4-tetrahydro-5H-indeno[1,2-d] pyrimidine-5-one by multi-component condensation
of 1,3 indanedione, aromatic aldehydes and urea/thiourea using phosphorus pentoxide in
ethanol under reflux condition. The simple work-up procedure and moderate to good
yield in short time are some important features of this protocol. The synthesized
compounds have been interpreted on the basis of their spectroscopic data. (Scheme I)
1

KEYWORDS: Biginelli Reaction, Phosphorous pentoxide, Dihydropyrimidones
INTRODUCTION
Nitrogen containing heterocyclic compound shows significant and precious biological
activities [1]. Since, last two decades, the synthesis of Dihydropyrimidones (DHPMs) and
their analogues have gained a considerable attention as synthetic target for current day
researchers due to their valuable and significant biological activities such as antibacterial
[2], antiviral [3], anti-inflammatory [4], antihypertensive [5], antitumor [6], α-adrenergic
antagonists [7] and HIV-gp-120-CD4-inhibitor [8] . It has very broad spectrum of
biological activities [9]. Moreover, DHPMs have been recently recognised as imperative
drugs in antihypertensive treatment, calcium channel blockers [10], and neuropeptide Y
antagonist [11]
.
Some of the analogues of DHPMs have been used as active ingredients in drugs, in this
compound (I) is potent calcium channel blockers [12] while compound (II) have excellent
anti-cancer activity [13]
.
2

Primitively, the first synthesis of DHPM was reported by an Italian Chemist Sci. Pietro
Biginelli in 1893 by a one pot cyclocondensation of aromatic aldehydes, ethyl aceto
acetate and urea in presence of strong mineral acid [14]. This original reaction was
suffered from drawbacks like, low yields and longer reaction time especially with
aliphatic aldehydes.
Owing to the vital significance in medicinal field the designing of DHPM’s was assigned
as a probe to a wide range of pharmaceuticals and other bio-significant molecules.
Consequently, till date a systematic pursuit has been lead by the current researchers in
order to innovate and develop the methodological approach in regards of yield, reaction
time and the catalyst to be used. Efforts made in the methodological enhancement for the
synthesis of DHPM’s promoted the use of various kinds of catalyst [15–18], multistep
synthesis[19], microwave irradiation[20], ultrasound irradiation[21] , ionic liquids [22] etc.
Multi-component reactions which employ three or more reactants combined in one pot
procedure way have accessed a considerable importance as compared to the conventional
multistep route as they furnish convenient isolation of complex molecule without any
separation of intermediate during the reaction process [23]. These features are important in
the early step of drug discovery by the screening of biological activities [24]. The inspired
interest of the organo-chemist in the MCR strategy lead to an outcome of wide spread
application of multicomponent theme deal with the modern demands of the contemporary
organic chemistry [25–30] by using different kinds of 1, 3-dicarbonyl compounds which
3

leads to generation of a new library of DHPMs like derivatives in order to find out new
potent bioactive compounds.
The encouraging reports on the smooth working of P2O5 in the organic transformations
[31] and the initial successful incorporation of phosphorous pentoxide for the original
Biginelli condensation [32] prompted us to extends its use for the Biginelli like
condensation of 1,3 indanedione, aromatic aldehydes and urea/thiourea to get 4-aryl-3,4-
dihydro-1H-indeno[1,2-d] pyrimidine-2,5-dione and 4- aryl -2-thioxo-1,2,3,4-tetrahydro-
5H-indeno[1,2-d] pyrimidine-5-one.
Literature survey reveals only one report available on the synthesis of indeno[1,2-d]
pyrimidines [33] which involves one pot condensation of benzaldehyde, 1, 3 indanedione
and urea/thiourea. This reported method has its own merits and demerits. In order to
establish a convenient and highly proficient synthetic methodology for the preparation of
these vital structural motifs evading several demerits of the previous reports and in the
continuation of our sincere efforts in the development of newer synthetic methodologies
[34], we put forth an efficient synthetic route for obtaining 3, 4-dihydro-1H-indeno [1, 2-d]
pyrimidine-2, 5-dione using phosphorous pentoxide through one pot multi-component
reaction. (Scheme I)
RESULT AND DISCUSSION
Initially, 1, 3 indanedione (0.14 g 1mmol), 2-Hydroxy benzaldehyde (0.12g 1mmol),
Urea (0.30g 5mmol) using catalytic amount of phosphorous pentoxide were refluxed on
water bath. After the completion of the reaction monitored by thin layer chromatography
4

the mixture was poured on the crushed ice with constant stirring. The extruded product
separated out was filtered and successively washed with aqueous ethanol to evade the
unconsumed 1, 3 indanedione impurity.
Phosphorous pentoxide is inexpensive reagent effective for the progress of the reaction.
Phosphorus pentoxide act as an acid catalyst increases the acidic condition in the reaction
which leads shorter reaction time [35]. It is good dehydrating reagent and soluble in water
is easily removed. The formed products were recrystalised from ethanol and analysed by
the spectroscopic data. The IR spectrum of 4-(2-hydroxyphenyl)-3,4-dihydro-1H-
indeno[1,2-d]pyrimidine-2,5-dione (Table-3 entry 1) shows absorption at 1637, 1701,
3251, and 3407 cm-1 while the H1 NMR of same compound exhibits singlet at δ 5.52 due
to methine proton, two broad singlet at δ 7.96 are the two –NH protons while eight
aromatic protons appear as multiplet between δ 6.67 to 7.56 the broad singlet at δ
10.60 is due to phenolic –OH. The obtained spectroscopic data and reported literature
values were found to be in good agreement with proposed structure. This initial result
inspired us to study this reaction in detail.
Therefore to investigate the efficiency of catalyst, the same reaction [Scheme 1] was
extended for various catalysts such as Na2CO3, Na2SO4, Cu nanoparticle, P-TSA etc. The
details of these studies have been summarized in Table 1.
5

The results obtained for the catalytical evaluation proved the P2O5 as an excellent agent
which extruded the desired product in good to excellent yield with a considerable
shortening in the reaction time.
Propelled by these encouraging results, optimization of required catalytical amount
[Table 2] was carried for the same trial reaction varying the quantities of phosphorous
pentoxide
As per our investigation, it has been concluded that 200 mg of phosphorus pentoxide is
sufficient quantity for the said reaction to get maximum yield of the product. On further
addition of catalyst, there is no any change in the yield or time of the reaction.
The solvent efficiency for the same protocol was evaluated altering the solvent with
water; however the desired reaction failed to proceed beyond the knoevenagel formation.
Consequently ethanol was considered appropriate solvent affording resultant
dihydropyrimidones in excellent yield. To assess the versatility of the method using
optimum quantity of catalyst [Table 2- Entry 4] the reaction was extended to variety of
aromatic and aliphatic aldehydes with simultaneous variation in the urea derivatives.
Regardless of the varied alterations made in the respective reactants the protocol yielded
similar products in the good to excellent yields. Moreover the variations in the aldehyde
both electron donating and electron withdrawing aldehydes have given good to excellent
yield of the product. All these results have been summarized in Table 3
6

The plausible mechanism for the formation of 4-phenyl-3,4-dihydro-1H-indeno[1,2-d]
pyrimidine-2,5-dione and 4-phenyl-2-thioxo-1,2,3,4-tetrahydro-5H-indeno[1,2-d]
pyrimidine-5-one has been shown in Scheme 2. The reaction may proceeds through the
condensation of 1, 3 indanedione 1 with aldehyde 2 gives Knoevenagel product 3. The
Michael addition of urea/thiourea 4 takes place on knoevenagel product followed by
successive cyclization, dehydration of 5 provide desired product 6. The essential role of
phosphorus pentoxide in this reaction is it act as an acid catalyst and dehydrating reagent,
which not only increases the rate of the reaction but it also helps for easy cyclization to
get desired product.(Scheme II)
CONCLUSION
We have successfully developed simple, clean and rapid method for the synthesis of 3, 4-
dihydro-1H-indeno [1, 2-d] pyrimidine -2, 5-dione derivative using phosphorous
pentoxide, which is an efficient and inexpensive reagent. The phosphorous pentoxide is
greatly assisted in the reaction which significantly develops one-step synthesis of
Biginelli like DHPMs in good to excellent yield and the synthesized compounds may
have very broad scope in biological investigations.
EXPERIMENTAL SECTION
The melting points were determined in open capillary were found to be uncorrected. The
purity of sample checked by thin-layer chromatography using silica gel 60-F 254 plates.
The reported compounds were confirmed by 1H NMR and IR while unreported
compounds were confirmed by, 1H NMR, IR, 13C NMR and Mass analysis. The 1H NMR
7

and13C NMR spectra were taken in DMSO-d6 using Brucker 300 MHz and 75 MHz or
Brucker 400 MHz and 100 MHz spectrophotometer with TMS as internal standard. IR
spectra were recorded on Shimadzu IR-450 FT-IR spectrophotometer. All the data found
were corrected with the proposed structure.
General Procedure For Synthesis Of 3, 4-Dihydropyrimidin-2(1H)-One.
The mixture of 1, 3 indanedione (1mmol), aromatic / aliphatic aldehydes (1mmol) and
urea/thiourea (5mmol) and phosphorous pentoxide (0.2 g) in 25 ml round bottom flask
were mixed thoroughly and refluxed on water bath using ethanol as a solvent. The
reaction is completed within 4-5 hours monitored by TLC. After completion, the mixture
was cooled, poured on the crushed ice. On stirring, desired product was separated. The
separated product was then filtered, washed with water and pet ether, dried and
recrystallised using ethanol to get pure product.
4-(2-hydroxyphenyl)-3,4-dihydro-1H-indeno[1,2-d]pyrimidine-2,5-dione (Entry 1 )
orange solid, m.p.196-200 0C (Lil.200-20434), yield (83 %), IR (KBr): 1637, 1701, 3251,
3407 cm-1; 1H NMR (300 MHz, DMSO-d6): δ 5.52 (s, 1H, -CH), 6.67-6.72 (m, 1H, HAr),
6.77-6.80 (d, 1H, HAr), 7.00- 7.04 (m, 2H, HAr), 7.20-7.33 (m, 3H, HAr), 7.54-7.56 (m,
1H, HAr), 7.96 (br.s, 2H, -NH), 10.60 (s, 1H, -OH) ), Elemental Anal. Found: C (69.78%)
H (4.08%) N (9.47%) Calcd for C17H12N2O3 = C (69.86%) H (4.14%) N (9.58%).
SUPPLEMENTAL MATERIAL
8

Supplemental data for this article can be accessed on the publisher’s website. Please
make the words “publisher’s website a live DOI link.
ACKNOWLEDGMENTS
The author (PPW) thanks to the DST, New Delhi for INSPIRE Fellowship,
[No.DST/INSPIRE Fellowship/2013/197] and also author (PVA) acknowledges the
UGC, New Delhi for sanctioning a major research project. [F. No. 39-786/2010(SR)].
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12

Table 1 Optimization of reaction conditions.
Entry Catalyst Solvent Time(hrs) Yield (%)
1
2
3
4
5
6
Na2CO3
Ethanol
Ethanol
Ethanol
Ethanol
Water
8
8
9
8
9
-
Na2SO4
-
Cu Nanoparticle
P-TSA
-
-
Cu Nanoparticle
-
Phosphorous pentoxide Ethanol 4-6
80-95
13

Table 2 Optimization of phosphorus pentoxide.
Entry Quantity of P2O5 (mg) Time (hrs.) Yield (%)
1.
2.
3.
4.
40
7.0
5.0
5.0
4-6
60
60
70
100
200
80
80-95
14

Table 3 Data for the synthesis of Dihydrpyrimidinones in the presence of phosphorus
pentoxide
Entry
1
R
X Time(hrs) Yield (%) m.p. Obs.0C
2-(OH)- C6H4
4-(Cl)- C6H4
4-(OCH3)- C6H4
C6H5
O 4
O 4
O 5
O 6
83
94
87
83
90
93
88
84
91
85
82
92
81
196-200 (200-204)33
216-217 (215-217)33
179-183 (180-183)33
173-175 (175-178)33
221-223 (220-223)33
200-204
2
3
4
5
4-(OH),3-(OCH3) -C6H3 O 5
6
3-(NO2)- C6H4
4-(OH)- C6H4
2-(OH)- C6H4
4-(Cl)- C6H4
4-(OCH3)- C6H4
C6H5
O 5
O 5
7
250-255
8
S
S
S
S
S
S
4
5
4
6
6
4
240-244 (240-243)33
183-185 (185-187)33
144-148 (144-147)33
250-252(249-252) 33
194-196 (196-198)33
245-250
9
10
11
12
13
14
15
4-(OH),3-(OCH3) -C6H3
4-(OH)-C6H4
nC3H7
O 4
O 5
-------
-------
---------
nC5H11
-----------
15

Scheme I. One pot synthesis of 3, 4-dihydropyrimidin-2(1H)-one derivatives.
16

Scheme II The plausible mechanism of the reaction.
17