Scientific paper
Ultrasound-promoted One-pot Synthesis of 8-Aryl-7,8-dihy dro- [1,3] -dioxolo [4,5-g] quinolin-6(5fl)-one Derivatives under Catalyst-free and Solvent-free
Con di tions
Davood Azarifar* and Davood Sheikh
Department of Chemistry, Bu-Ali Sina University, Zip Code 65178, Hamedan, Iran
* Corresponding author: E-mail: azarifar@basu.ac.ir; Fax +98(811)8257407
Received: 07-02-2012
Abstract
An ultrasound-accelerated one-pot procedure has been explored for the synthesis of 8-aryl-7,8-dihydro-[1,3]-dioxo-lo[4,5-g]quinolin-6(5H)-one derivatives using the reaction between 3,4-methylendioxyaniline 1, aldehyde 2 and iso-propylidene malonate 3 under catalyst-free and solvent-free conditions. High yields of the products, mild reaction condition, environmentally friendly procedure, catalyst- and solvent-free conditions are the main advantages of this protocol.
Keywords: Quinolin-6(5H)-ones, Ultrasound-irradiation, Catalyst-free, Solvent-free, One-pot reaction
1. Introduction
Substituted quinolines are one of the oldest known classes of pharmaceutical agents and their relevance in chemotherapy especially against malaria is widely known.1 Beside antimalarials, a spectrum of other pharmacological activities2 has been the major reason for the development of novel and efficient synthesis of this hete-rocycle. As a result, the recent past has witnessed the publication of several simple and elegant synthesis of substituted quinolines.3
Nevertheless, a new, solvent-free, one-pot method from readily accessible starting materials, which would permit delivery of this motif decorated with functional groups amenable to further diversification, should be of great synthetic relevance.
Multi-component reactions (MCRs) have proved to be notably successful in generating products in a single synthetic operation.4-5 The development of new MCRs6 and improvement of known multi-component reactions are the subjects of considerable current interest.
Recently, an area of intense synthetic endeavor has emphasized the use and design of reagents without the use of any solvent. Avoiding organic solvents during the reactions in organic synthesis leads to clean, efficient and
cost-effective technology. In solid state reactions, work up is considerably simplified, cost is reduced, increased amounts of reactants can be used in the same equipment, reactivities and sometimes selectivities are enhanced without dilution.7
In recent years, the use of ultrasound in organic transformations is well known to enhance reaction rates, yields and selectivity of reaction. In several cases, it facilitates organic transformation at ambient conditions which otherwise require drastic conditions of temperature and pressure.8-9
Sonochemistry can be defined as the chemical effect caused by ultrasound in a broad sense, but it is generally understood as the chemical outcome of acoustic cavita-tion, evolution and collapse of micro bubbles as a result of ultrasonic irradiation. According to the most widely accepted hot spot theory, the gas phase of the cavity reaches high temperatures (5000 K) and pressures (170 MPa).10 As the life time of this hot spot is very short (10-6 s), the rate of the temperature variation is as rapid as 1010 K s-1.11
Because of their wide range of biological, industrial and synthetic applications, substituted quinolines have recently received a great deal of attention. In continuation of our work on solvent-free, ultrasound conditions,12 we present here, for the first time, a simple, mild and efficient
Scheme 1. One-pot three-component reaction of 3,4-methylendioxyaniline 1, aromatic aldehyde 2 and isopropylidene malonate 3 under ultrasound irradiation.
synthesis of 8-aryl-7,8-dihydro-[1,3]-dioxolo[4,5-g]qui-nolin-6(5H)-ones in high yields (Scheme 1).
2. Experimental
Chemicals used in this work were purchased from Aldrich and Merck chemical companies and used without purification. IR spectra were recorded on a Shi-madzu 435-U-04 FT spectrometer as KBr pellets. and 13C NMR spectra were measured in CDCl3 with a Bruker DRX-400 Avance instrument at 400 and 100 MHz, respectively, using Me4Si as internal standard. Mass spectra were recorded with a spectrometer Finni-gan-MAT 8430 operating at an ionization potential of 70 eV. Melting points were measured on a SMPI apparatus. Elemental analyses for C, H and N were performed using a Perkin-Elmer 2400 series analyzer. Ultra-sonication was performed in a Transsoni 660/H ultrasound cleaner with a frequency of 35 kHz and an output power of 70 W. The reactions were performed in open vessels.
2.1. Ultrasound-promoted Condensation of 3,4-Methylendioxyaniline, Isopropylidene Malonate and Aromatic Aldehydes
General procedure. A mixture of 3,4-methylendioxyani-line 1 (0.132 g, 1 mmol), aldehyde 2 (1 mmol) and isopropylidene malonate 3 (0.15 g, 1 mmol) in a flask was placed in a water bath and sonicated at 30-40 °C for an appropriate time (Tables 1 and 2) until the reaction was completed as monitored by TLC (n-hexane/EtOAc; 2:1). The reaction mixture was then washed with water and crude product purified on 20 x 20 cm2 TLC plates coated with silica gel 60 HF-254 using n-hexane/EtOAc (2:1) as the eluent. The separated products were first exposed to air for few minutes and then dried in an oven at 100 °C. For further purification, the products were crystallized from MeOH. The structures of these products were found to be the expected 8-aryl-7,8-dihydro-[1,3]-dioxolo[4,5-g]quinolin-6(5#)-ones 4a-i confirmed by their spectral data (IR, 1H and 13C NMR, MS) and elemental analysis as given below.
8-Phenyl-7,8-dihydro-[1,3]-dioxolo[4,5-g]quinolin-6(5H)-one (4a): Brown solid; m.p. 193-195 °C, IR (KBr) (vmax, cm-1): 3191 (NH), 1674 (C=O); MS m/z (%): 267 (M); 1H NMR (400 MHz, CDCl3): SH 3.15-3.08 (2H, m, H7), 4.30-4.27 (1H, t, H8), 5.19 (2H, s, OCH2), 6.33 (1H, s, Ar-H), 7.41-7.21 (5H, m, Ar-H), 8.49 (1H, s, NH); 13 C NMR (100 MHz, CDCl3): SC 39.7, 43.7, 97.7, 128.3,
128.5,	128.7, 128.8, 128.9, 129.0, 129.1, 129.2, 129.5,
129.6,	168.1; Anal. Calcd. for C16H13NO3: C, 71.91, H, 4.86, N, 5.24; found C, 71.76, H, 4.74, N, 5.12.
8-(4-Methylphenyl)-7,8-dihydro-[1,3]-dioxolo[4,5-g]quinolin-6(5H)-one (4b): Brown solid; m.p. 203-205 °C; IR (KBr) (vmax, cm-1): 3291 (NH), 1671 (C=O); MS m/z (%): 281 (M); 1H NMR (400 MHz, CDCl3): SH 1.09 (3H, s, CH3), 2.97-2.83 (2H, m, H7), 4.69-4.66 (1H, t, H8), 6.13 (2H, s, OCH2), 7.26 (1H, s, Ar-H), 7.34-7.32 (2H, d, Ar-H), 7.48 (1H, s, Ar-H), 7.58 (1H, s, NH), 8.04-8.02 (2H, d, Ar-H); 13 C NMR (100 MHz, CDCl3): SC 21.3, 31.9, 43.0, 99.3, 101.6, 123.8, 127.1, 128.3, 129.5, 129.7, 129.8, 138.9, 143.6, 147.6, 172.5; Anal. Calcd. for C17H15NO3: C, 72.59, H, 5.33, N, 4.98; found C, 72.50, H, 5.25, N, 5.05.
8-(4-Chlorophenyl)-7,8-dihydro-[1,3]-dioxolo[4,5-g]quinolin-6(5H)-one (4c): Pale brown solid; m.p. 209211 °C; IR (KBr) (vmax, cm-1): 3205 (NH), 1676 (C=O); MS m/z (%): 300 (M), 302 (M+2); 1H NMR (400 MHz, CDCl3): SH 2.95-2.84 (2H, m, H7), 4.25-4.18 (1H, t, H8), 5.89 (2H, s, OCH2), 6.38 (1H, s, Ar-H), 6.44 (1H, s, Ar-H), 7.45-7.20 (4H, m, Ar-H), 8.83 (1H, s, NH); 13 C NMR (100 MHz, CDCl3): SC 36.1, 40.1, 98.3, 104.6, 115.2, 122.1, 126.5, 128.3, 130.4, 133.2, 140.5, 145.1, 148.2, 169.4; Anal. Calcd. for C16H12ClNO3: C, 63.68, H, 3.98, N, 4.64; found C, 63.52, H, 4.06, N, 4.74.
8-(4-Methoxyphenyl)-7,8-dihydro-[1,3]-dioxolo[4,5-g]quinolin-6(5H)-one (4d): Brown solid; m.p. 235-237 °C; IR (KBr) (vmax, cm-1): 3350 (NH), 1665 (C=O); MS m/z (%): 297 (M); 1H NMR (400 MHz, CDCl3): SH 2.88-2.81 (2H, m, H7), 3.65 (3H, s, OCH3), 4.64-4.53 (1H, t, H8), 5.90 (2H, s, OCH2), 6.38 (1H, s, Ar-H), 6.43 (1H, s, Ar-H), 7.40-6.77 (4H, m, Ar-H), 8.87 (1H, s, NH); 13 C NMR (100 MHz, CDCl3): SC 34.7, 38.4, 57.1, 97.9, 103.2, 112.4, 122.6, 128.6, 130.6, 134.7, 140.4, 145.4,
153.7, 156.3, 170.8; Anal. Calcd. for C17H15NO4: C, 68.68, H, 5.05, N, 4.71; found C, 68.78, H, 4.89, N, 4.64.
8-(2,4-Dichlorophenyl)-7,8-dihydro-[1,3]-dioxolo[4,5-g]quinolin-6(5Ä)-one (4e): Pale cream solid; m.p. 254256 °C; IR (KBr) (vmax, cm-1): 3206 (NH), 1675 (C=O); MS m/z (%): 335 (M), 337 (M+2), 339 (M+4); 1H NMR (400 MHz, CDCl3): SH 2.97-2.83 (2H, m, H7), 4.69-4.66 (1H, t, H8), 5.96 (2H, s, OCH2), 6.43 (1H, s, Ar-H), 6.48 (1H, s, Ar-H), 7.47-6.87 (3H, m, Ar-H), 8.72 (1H, s, NH); 13 C NMR (100 MHz, CDCl3): SC 36.8, 38.1, 97.9, 101.5, 108.3, 116.9, 127.7, 129.8, 129.9, 131.7, 133.7, 134.2, 137.5, 144.0, 147.7, 169.8; Anal. Calcd. for C16H11Cl2NO3: C, 57.14, H, 3.27, N, 4.16; found C, 57.06, H, 3.39, NN, 4.24.
8-(2-Chlorophenyl)-7,8-dihydro-[1,3]-dioxolo[4,5-g] quinolin-6(5fl)-one (4f): Brown solid; m.p. 200-202 °C; IR (KBr) (vmax, cm-1): 3198 (NH), 1679 (C=O);MS m/z (%): 301 (M), 303 (M+2); 1H NMR (400 MHz, CDCl3 ): SH 2.94-2.92 (2H, m, H7), 4.76-4.73 (1H, t, H8), 5.95 (2H, s, OCH2), 7.46-6.44 (6H, m, Ar-H), 8.29 (1H, s, NH); 13 C NMR (100 MHz, CDCl3): SC 34.4, 38.5, 97.7, 108.4, 112.2, 115.7, 120.9, 127.4, 128.6, 128.9, 130.1, 138.8, 143.9, 147.5, 170.6; Anal. Calcd. for C16H12ClNO3: C, 63.68, H, 3.98, N, 4.64; found C, 63.56, H, 4.06, N, 43.52.
8-(2-Nitrophenyl)-7,8-dihydro-[1,3]-dioxolo[4,5-g]qui-nolin-6(5fl)-one (4g): Brown solid; m.p. 203-205 °C; IR (KBr) (vmax, cm-1): 3193 (NH), 1674 (C=O); MS m/z (%): 312 (M); ^ NMR (400 MHz, CDCl3): SH 2.74-2.72 (2H, m, H7), 4.26-4.23 (1H, t, H8), 6.15 (2H, s, OCH2), 7.95-7.41 (7H, m, NH, Ar-H); 13 C NMR (100 MHz, CDCl3): SC 29.7, 31.9, 99.3, 103.2, 108.4, 117.8, 127.2, 128.43 1295.4, 129.6, 129.7, 138.8, 143.8, 157.1, 160.3, 176.5; Anal. Calcd. for C 8.97; found C, 61.70, H, 3.93, N, 8.94.
16H12N2O5: C, 61.53, H, 3.84, N,
8-(2-Methoxyphenyl)-7,8-dihydro-[1,3]-dioxolo[4,5-g] quinolm-6(5ff)-one (4h): Pale yellow solid; m.p. 223-225 °C; IR (KBr) (vmax, cm-1): 3229 (NH), 1683 (C=O); MS m/z (%): 297 (MpH NMR (400 MHz, CDCl3): SH 2.97-2.83 (2H, m, H7), 3.88 (3H, s, OCH3), 4.63-4.60 (1H, t, H8), 5.93 (2H, s, OCH2), 6.41 (1H, s, Ar-H), 6.47 (1H, s, Ar-H), 6.89-6.88 (2H, m, Ar-H), 6.94-6.92 (1H, d, Ar-H), 7.26-7.24 (1H, dd, Ar-H), 8.04 (1H, s, NH); 13 C NMR (100 MHz, CDCl3): 8C 35.7, 39.1, 55.3, 97.5, 101.3,
108.5,	110.6, 118.8, 120.8, 128.2, 128.3, 131.6, 138.3,
143.6,	151.2, 155.0, 170.4; Anal. Calcd. for C17H15NO4: C, 68.68, H, 5.05, N 4.71; found C, 68.84, H, 5.12, N, 4.83.
8-(3-Bromophenyl)-7,8-dihydro-[1,3]-dioxolo[4,5-g] qumolm-6(5tf)-one (4i): Pale yellow solid; m.p. 207-209 °C; IR (KBr) (vmax, cm-1): 3194 (NH), 1672 (C=O); MS m/z (%): 345 (M), 347 (M+2); 1H NMR (400 MHz, CDCl3): SH
2.93-2.85 (2H, m, H7), 4.19-4.16 (1H, t, H8), 5.98 (2H, s, OCH2), 6.42 (1H, s, Ar-H), 6.46 (1H, s, Ar-H), 7.25-7.12 (2H, m, Ar-H), 7.44-7.42 (2H, d, Ar-H), 8.42 (1H, s, NH); 13 C NMR (100 MHz, CDCl3): SC 39.3, 41.8, 101.5, 101.6, 101.7, 108.4, 108.7, 118.1 123.0, 126.4, 128.8, 130.5, 130.6, 130.8, 130.9, 169.9; Anal. Calcd. for C16H12BrNO3: C, 55.50, H, 3.46, N, 4.04; found C, 55.64, H, 3.54, IN 3.95.
3. Results and Discussion
In order to establish the reaction conditions, the reaction of 3,4-methylendioxyaniline, benzaldehyde and isopropylidene malonate was chosen as a model reaction (Table 2, Entry a). The effects of solvent and conditions on the rate and yield of the reaction were studied using different solvents such as MeOH, MeCN, DMF, EtOAc, Et2O, CHCl3, CCl4, n-hexane as well as solvent-free condition both under ultrasonication and conventional heating at various temperatures (Table 1). The results summarized in Table 1 indicated that the best result in terms of yield and reaction rate was obtained under solvent-free and ultrasound irradiation conditions at 30-40 °C (Entry 1). However, as shown in this Table, the yields of the reaction obtained using the solvents MeCN (75%), EtOAc (76%) and DMF (78%) are comparable with that obtained under solvent-free condition.
Table 1. Screening of the solvents and conditions for the synthesis of 8-aryl-7,8-dihydro-[1,3]-dioxolo[4,5-g]quinolin-6(5ff)-onea
Entry Conditions		Method	Time (min)	Yield1 (%)
1	Solvent-free / 30-40 °C	ultrasound	50	83
2	MeOH / 30-40 °C	ultrasound	60	70
3	MeCN / 30-40 °C	ultrasound	60	75
4	EtOAc / 30-40 °C	ultrasound	60	76
5	DMF / 30-40 °C	ultrasound	60	78
6	CCl4 / 30-40 °C	ultrasound	60	69
7	Et20 / 30-40 °C	ultrasound	60	73
8	n-hexane / 30-40 °C	ultrasound	60	60
9	Solvent-free / rt	thermal	60	74
10	Solvent-free / 60 °C	thermal	60	72
11	Solvent-free / 100 °C	thermal	60	71
12	Solvent-free / reflux	thermal	60	71
13	MeOH / rt	thermal	60	65
14	MeCN / rt	thermal	60	69
15	EtOAc / rt	thermal	60	71
16	DMF / rt	thermal	60	73
17	CHCl3 / rt	thermal	60	67
18	Et2O /3 rt	thermal	60	66
19	CCl4 / rt	thermal	60	65
20	n-hexane /rt	thermal	60	55
a Conditions: 3,4-methylendioxyaniline (1 mmol), benzaldehyde (1 mmol), isopropylidene malonate (1 mmol), solvent (2 mL). b Isolated yields.
b
The scope of the reaction was extended to a variety of structurally diverse aldehydes using the optimized conditions. The results obtained are summarized in Table 2. As seen in this table, the aromatic aldehydes having electron-donating as well as electron-withdrawing groups were uniformly transformed into the corresponding 8-aryl-7,8-dihydro-[1,3]-dioxolo[4,5-g]quinolin-6(5H)-ones in high yields (76-88%) within 60-75 min. All of the products 4 exhibited a multiplet in the region 3.15-2.74 ppm for H-7 and a triplet in the region 4.76-4.16 ppm for H-8 in their 1H NMR spectra, and three distinguishing peaks in the regions 43.7-31.9 (C-8), 41.8-29.7 (C-7) and 176.5-168.1 (C=O) ppm in their 13C NMR spectra.
A possible mechanism to explain the formation of the products 4a-i is depicted in Scheme 2. The formation
Table 2. Ultrasound-promoted synthesis of 8-aryl-7,8-dihydro-[1,3]-dioxolo[4,5-g]quinolin-6(5H)-one derivatives 4a-ia.
Entry Ar	Product 4	Time Yield b
(min) (%)
Entry Ar	Product 4	Time Yield b
(min) (%)
a Conditions: 3,4-methylendioxyaniline (1 mmol), aromatic aldehyde (1 mmol), isopropylidene malonate (1 mmol), sonication at 30-40 °C. b Isolated yield.
of products 4a-i can be rationalized by initial formation of heterocyclic system 5 through the standard Knoevenagel condensation of 3 with the aromatic aldehyde 2. Subsequent Michael-type addition of 3,4-methylenedioxyanilin 1 to 5 followed successively by cyclization, dehydration and air oxidation affords the corresponding products 4a-i.
4. Conclusion
We have described an ultrasound-promoted three-component one-pot procedure for the synthesis of 8-aryl-7,8-dihydro- [1,3] -dioxolo [4,5-g] quinolin-6(5#)-one derivatives under catalyst-free and solvent-free conditions. High yields, environmentally friendly nature, simplicity and mildness are the main merits of this method.
5. Acknowledgements
The authors wish to thank the Bu-Ali Sina University Research Council for the financial support to carry out this research.
Scheme 2. Mechanism for synthesis 8-aryl-7,8-dihydro-[1,3]-dioxolo[4,5-g]quinolin-6(5H)-ones.
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Povzetek
Raziskali smo sintezo 8-aril-7,8-dihidro-[1,3]-dioksolo[4,5-g]kinolin-6(5ff)-onskih derivatov, ki nastanejo pri reakciji med 3,4-metilendioksianilinom 1, aldehidom 2 and izopropiliden malonatom 3 brez uporabe katalizatorjev in topila. Reakcija je pospešena z uporabo ultrazvočnega obsevanja in poteka v eni sami posodi ("one-pot" postopek). Visoki izkoristki produktov, nežni reakcijski pogoji, okolju prijazni postopki ter pogoji brez uporabe katalizatorjev in topil so glavne odlike tega sinteznega pristopa.