Vilsmeier Reagent: An efficient reagent for the transformation of 2-aminobenzamides into quinazolin-4(3 h)-one derivatives

Article abstract of DOI:10.1080/00397911.2013.811528

Clean and easy preparation of quinazolin-4(3H)-one derivatives using 2-aminobenzamides and Vilsmeier reagent is described. 2-Aminobenzamides were converted into the corresponding quinazolinones under mild and efficient conditions, in good yields without undesirable by-products.

Full text of DOI:10.1080/00397911.2013.811528

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Vilsmeier Reagent: An Efficient
Reagent for the Transformation of 2-
Aminobenzamides into Quinazolin-4(3H)-
one Derivatives
Soghra Farzipour a , Mina Saeedi b , Mohammad Mahdavi b , Hossein
Yavari b , Mohammadreza Mirzahekmati b , Nasser Ghaemi a , Alireza
Foroumadi b & Abbas Shafiee b
a School of Chemistry , College of Science, University of Tehran ,
Tehran , Iran
b Department of Medicinal Chemistry , Faculty of Pharmacy and
Pharmaceutical Sciences Research Center, Tehran University of
Medical Sciences , Tehran , Iran
Published online: 27 Dec 2013.
To cite this article: Soghra Farzipour , Mina Saeedi , Mohammad Mahdavi , Hossein Yavari ,
Mohammadreza Mirzahekmati , Nasser Ghaemi , Alireza Foroumadi & Abbas Shafiee (2014) Vilsmeier
Reagent: An Efficient Reagent for the Transformation of 2-Aminobenzamides into Quinazolin-4(3H)-
one Derivatives, Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 44:4, 481-487, DOI: 10.1080/00397911.2013.811528
To link to this article: http://dx.doi.org/10.1080/00397911.2013.811528
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Synthetic Communications1, 44: 481–487, 2014
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2013.811528
VILSMEIER REAGENT: AN EFFICIENT REAGENT FOR
THE TRANSFORMATION OF 2-AMINOBENZAMIDES
INTO QUINAZOLIN-4(3H)-ONE DERIVATIVES
Soghra Farzipour,1 Mina Saeedi,2 Mohammad Mahdavi,2
Hossein Yavari,2 Mohammadreza Mirzahekmati,2
Nasser Ghaemi,1 Alireza Foroumadi,2 and Abbas Shafiee2
1School of Chemistry, College of Science, University of Tehran, Tehran, Iran
2Department of Medicinal Chemistry, Faculty of Pharmacy and
Pharmaceutical Sciences Research Center, Tehran University of Medical
Sciences, Tehran, Iran
GRAPHICAL ABSTRACT
Abstract Clean and easy preparation of quinazolin-4(3H)-one derivatives using
2-aminobenzamides and Vilsmeier reagent is described. 2-Aminobenzamides were converted
into the corresponding quinazolinones under mild and efficient conditions, in good yields
without undesirable by-products.
[Supplementary materials are available for this article. Go to the publisher’s online
edition of Synthetic Communications1 for the following free supplemental resource(s):
Full experimental and spectral details.]
Keywords 2-Aminobenzamides; heterocycles; isotoic anhydride; 4(3H)-quinazolinones;
Vilsmeier reagent
INTRODUCTION
The Vilsmeier reagent 3 (Scheme 1) was introduced by Anton Vilsmeier and
Albrecht Haack in 1927. For the formylation of activated electron rich aromatic
compounds or olefins,[1] it has been attractive for synthetic chemists to prepare dif-
ferent types of heterocyclic compounds.[2] This efficient reagent is easily synthesized
by the reaction of N,N-dimethylformamide 1 (DMF) and chlorinating agents such as
phosphorus oxychloride (POCl3) 2, phosphorus trichloride (PCl3), oxalyl chloride
(COCl)2, and thionyl chloride (SOCl2) (Scheme 1).[3]
Received April 5, 2013.
Address correspondence to Abbas Shafiee, Department of Medicinal Chemistry, Faculty of
Pharmacy and Pharmaceutical Sciences Research Centre, Tehran University of Medical Science, Tehran
14176, Iran. E-mail: ashafiee@ams.ac.ir
481

482
S. FARZIPOUR ET AL.
Scheme 1. Preparation of Vilsmeier reagent 3.
Scheme 2. Synthesis of 4(3H)-quinazolinones 5.
Successful and versatile transformations in organic chemistry using Vilsmeier
reagent or its modified form,[4] such as formylation,[5] cyclohaloaddition,[2a] cycliza-
tion,[6] and ring annulations,[7] led to the formation of various heterocycles. The
results stimulated us to investigate synthesis of 4(3H)-quinazolinones as biologically
important compounds using Vilsmeier reagent and to present an efficient surrogate
for the synthesis of the title compounds 5 (Scheme 2).
4(3H)-Quinazolinones are an important class of N-heterocycles owing to their
presence in the numerous natural products and synthetic organic compounds along
with proficient various pharmacological properties.[8] They have been used as
antiulcer,[9] anti-inflammatory,[10] anticancer,[11] hypolipidemic,[12] and anticonvul-
sant agents.[13] Also quinazolin-4(3H)-one skeleton is found in a range of biologically
important natural products including febrifugine and isofebrifugine, which possess
antimalarial activity.[14] Although a wide range of routes has been reported for the
synthesis of 4(3H)-quinazolinones,[15] biological properties of this class of hetero-
cycles has encouraged us to design a simple and efficient approach for their
preparation.
RESULTS AND DISCUSSION
We recently reported novel synthesis of 1,4-benzodiazepine-3,5-diones under
Bargellini reaction conditions,[16] benzo[d][1,3,2]diazaborinin-4(1H)-one,[17] and
3-alkyl-2-(alkylamino)quinazolin-4(3H)-one,[18] using 2-aminobenzamide derivatives
as an proficient ambident nucleophile. In continuation of our studies on the synthesis
of different kinds of heterocycles,[19] herein, we report synthesis of 3-substituted-
4(3H)-quinazolinones 5 using 2-aminobenzamides 4 and Vilsmeier reagent 3 at
ambient temperature (Scheme 2).
Our investigations were initiated by preparing 2-aminobenzamide derivatives 4
and Vilsmeier reagent 3. According to our previous works,[16–18] all 2-aminobenza-
mides 4 were synthesized by a simple and green procedure. Equivalent amounts of

QUINAZOLIN-4(3H)-ONES
483
Table 1. Synthesis of 4(3H)-quinazolinones 5
Mp (ꢀC)
Observed Reported Yield (%)a
Entry
1
2-Aminobenzamides 4
Product 5
5a
5b
5c
72–74
85–87
68–70
70–72[15a]
87–88[15f]
65[15e]
80
80
75
65
82
75
80
75
2
3
4
5
6
7
8
5d 145–147 141–142[15a]
5e 155–156 154–155[15h]
5f 117–119
116[15c]
5g 137–138 134–135[15a]
5h 269–270
—
9
5i 109–110 107–109[15g]
80
77
10
5j 120–122
—
aIsolated yields.

484
S. FARZIPOUR ET AL.
Scheme 3. Proposed sequences for the synthesis of 4(3H)-quinazolinones 5.
amines 6 and isatoic anhydride 7 were reacted in water at room temperature for 2 h.
After this time the precipitated products were filtered and dried. The obtained 2-ami-
nobenzamides 4 were pure and used for further reactions.
Vilsmeier reagent 3 was simply prepared by stirring a mixture of dimethylfor-
mamide DMF 1 (4.6 mL, 60 mmol) and phosphorus oxychloride 2 (5.6 mL, 60 mmol)
at room temperature for 30 min. Then 2-amino-N-benzylbenzamide 4e (2 mmol) was
added to reaction mixture and the reaction continued at room temperature for 8 h.
After completion of reaction, the corresponding product, 5e, was obtained in 82%
yield. We found that in situ preparation of reagent is sufficient to achieve the
condensation reaction and no by-product is obtained. Any salt which formed during
the reaction was removed by simple aqueous workup.
Good results with simple and clean procedure encouraged us to expand our
method to utilize different 2-aminobenzamide derivatives 4 in these reactions
(Scheme 2) and synthesize various 4(3H)-quinazolinones 5 (Table 1). The structures
of all products were confirmed by 1H NMR and 13C NMR spectroscopy and
compared with those reported in the literature.[15]
A proposed sequence is depicted schematically in Scheme 3. The initial step
involves nucleophilic attack by an amino group in 2-aminobenzamide derivatives
4 at the electrophilic carbon of Vilsmeier reagent 3 to form 8 and then iminium salt
9. Intramolecular cyclization (10) followed by the loss of NH(Me)2 group leads to
the formation of product 5.
CONCLUSION
In conclusion, we have implemented an efficient, clean, and user-friendly app-
roach for the synthesis of diversely 3-substituted-4(3H)-quinazolinone derivatives.
This approach involves the condensation reaction of 2-aminobenzamides, derived
from isatoic anhydride and various amines; and Vilsmeier reagent at room tempera-
ture without any by-products. Although previously reported procedures gave the
title compounds in good yields, our method offered them from available starting
material without utilizing expensive catalysts or microwave irradiation.

QUINAZOLIN-4(3H)-ONES
485
EXPERIMENTAL
Melting points were taken on a Kofler hot stage apparatus and are uncorrected.
1H-and 13C(NMR) spectra were recorded on Bruker FT-500 or 400, using tetra-
methylsilane (TMS) as an internal standard. The infrared (IR) spectra were obtained
on a Nicolet Magna FTIR 550 spectrophotometer (in KBr). All reagents and solvents
were obtained from Merck and Aldrich and used without any purification. Thin-layer
chromatography (TLC) was performed using silica gel 60=Kieselguhr F254 precoated
on aluminum sheets (thickness 0.2 mm), commercially available from Merck.
Visualization of spots on TLC plate was accomplished with ultraviolet (UV) light.
Synthesis of 4(3H)-Quinazolinone Derivatives 5: General Procedure
A mixture of dimethyl formamide DMF 1 (60 mmol, 4.6 mL) and phosphorus
oxychloride POCl3 2 (60 mmol, 5.6 mL) was stirred at room temperature for 35 min.
Then, 2-aminobenzamide derivatives 4 (2 mmol) were added to the reaction mixture
and the stirring was continued for 8–12 h. Upon completion of reaction (checked by
TLC), the solution was added to water and extracted with ethyl acetate (3 ꢁ 50 mL).
The organic layer was separated, dried (Na2SO4), and concentrated in vacuo to yield
the crude product, which was purified by recrystallization from ethyl acetate.
3-Butylquinazolin-4(3H)-one (5a)
1
Yield: 80%, yellow crystals. Mp 72–74ꢀC (70–72 ꢀC)[15a]; H NMR (DMSO-d6,
500 MHz): dH ¼ 8.42 (s, 1H, H2), 8.16 (dd, J ¼ 8.0, 1.5 Hz, 1H, H5), 7.81 (dt, J ¼ 8.0,
1.5Hz, 1H, H7), 7.68 (d, J ¼ 8.0 Hz, 1H, H8), 7.54 (t, J ¼ 8.0Hz, 1H, H6), 3.98 (t,
J ¼ 7.4 Hz, NCH2CH2CH2CH3), 1.68 (quintet, J ¼ 7.4 Hz, NCH2CH2CH2CH3), 1.31
(sextet, J ¼ 7.4 Hz,NCH2CH2CH2CH3), 0.91 (t, J ¼ 7.4 Hz, NCH2CH2-CH2CH3).Anal.
calcd. for C12H14N2O: C, 71.26; H, 6.98; N, 13.85. Found: C, 71.51; H, 7.14; N, 13.98.
3-(4-Methoxybenzyl)quinazolin-4(3H)-one (5g)
Yield: 80%, yellow crystals. Mp 137–138 ꢀC (134–135 ꢀC)[15a] 1H NMR
;
(DMSO-d6, 500 MHz): dH ¼ 8.59 (s, 1H, H2), 8.16 (d, J ¼ 7.7 Hz, 1H, H5), 7.84 (t,
J ¼ 7.7 Hz, 1H, H7), 7.70 (d, J ¼ 7.7 Hz, 1H, H8), 7.56 (t, J ¼ 7.7 Hz, 1H, H6), 7.36
(d, J ¼ 8.0 Hz, 2H, H2’, H6’), 6.91 (d, J ¼ 8.0 Hz, 2H, H3’, H5’), 5.13 (s, 2H, NCH2),
3.72 (s, 3H, OCH3). Anal. calcd, for C16H14N2O2: C, 72.16; H, 5.30; N, 10.52.
Found: C, 71.97; H, 5.61; N, 10.32.
SUPPORTING INFORMATION
1
Full experimental details and H and 13C NMR spectra are available. This
material can be found via the Supplementary Content section of this article’s Web page.
ACKNOWLEDGMENTS
This research was supported by grants from the Research Council of Tehran
University of Medical Sciences, the Iran National Science Foundation (INSF),
and Iran National Elite Foundation (INEF).

486
S. FARZIPOUR ET AL.
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