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An efficient method for synthesis of stable phosphorus ylides and 1,4-diionic organophosphorus compounds in the presence of sodium dodecyl sulfate in aqueous media
*Corresponding author. Tel./fax: +98 5412446565 mt_maghsoodlou@yahoo.com (Malek Taher Maghsoodlou)
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Received: ,
Accepted: ,
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.
Available online 15 June 2010
Abstract
Stable crystalline phosphorus ylides and 1,4-diionic organophosphorus compounds were obtained in good to excellent yields from the 1:1:1 addition reaction between triphenylphosphine, dialkyl acetylenedicarboxylates and β-dicarbonyl or heterocyclic compounds, such as diethyl malonate, acetyl acetone, 1,3-diphenyl propane-1,3-dione, 1,3-dimethylbarbituric acid, meldrum’s acid, 2-benzoxazolinone, benzotirazole, and 2-thiazoline-2-thiol in the presence of sodium dodecyl sulfate as a surfactant in water. Green synthesis, mild conditions, decreasing timescale of reaction, low cost, and easy workup are the main advantages of this method.
Keywords
Stable phosphorous ylides
1,4-Diionic organophosphorus compounds
Sodium dodecyl sulfate
Aqueous media
1 Introduction
With the increasing environmental concerns and the regulatory constraints faced by the chemical and pharmaceutical industries, development of environmentally benign organic reactions has become a crucial and demanding research area in modern organic chemical research (Anastas, 1998). Therefore, more and more chemists are devoted to the researching “green synthesis” which means the reagent, solvent, and surfactant are environmentally friendly in the organic chemical reactions. Recently, organic reactions in water without use of harmful organic solvents have attracted much attention, because water is a cheap, safe, and environmentally benign solvent (Yavari and Islami, 1998; Yavari et al., 1999). Previously, the scant solubility of reactants was the main reason preventing the use of water as a green solvent. Various reactions that are traditionally carried out in organic solvents have been equally successful or even more effective in aqueous media (Venkatraman and Li, 2001; Tian et al., 2001). The use of water as a green solvent in organic reaction in place of commonly used organic solvents has been reported in the filed of green chemistry (Breslow and Maitra, 1984; Delair and Luche, 1989). This advantage prompted us to use towards the synthesis of stable phosphorus ylides and 1,4-diionic organophosphorus compounds in the presence of sodium dodecyl sulfate in aqueous media.
2 Experimental
Dialkyl acetylenedicarboxylates, diethyl malonate, acetyl acetone, 1,3-diphenyl propane-1,3-dione, 1,3-dimethylbarbituric acid, meldrum’s acid, 2-benzoxazolinone, benzotirazole, 2-thiazoline-2-thiol, triphenylphosphine, and sodium dodecyl sulfate were obtained from Fluka or Merck companies, and used without additional purification. Melting points were measured by Electrothermal 9100 apparatus. IR spectra were recorded on a Shimadzu IR-460 spectrometer (pellets with KBr). 1H NMR spectra were measured on a BRUKER DRX-500 AVANCE spectrometer instrument with CDCl3 as solvent.
2.1 General procedure for preparation of stable phosphorous ylides and 1,4-diionic organophosphorus compounds
To a magnetically stirred solution of a C–H or N–H acid (1 mmol) in water (5 mL), a mixture of triphenylphosphine (0.26 g, 1 mmol) and sodium dodecyl sulfate (0.009 g, 0.1 mmol) was added. Then dimethyl acetylenedicarboxylate (0.14 g, 1 mmol) was added, dropwise, at room temperature for more than 10 min. After approximately 1–2 h stirring, the solution was filtered and the solid phase washed with dichloromethane. The solvent evaporated under reduce pressure and colorless precipitate washed with cold diethyl ether.
2.2 Selected specteral data
2.2.1 Dimethyl 2-[di(ethoxycarbonyl) methyl]-3-(triphenylphosphoranylidene)-butane-1,4-dioate (3a)
Colorless crystals, m.p. 192–193 °C, yield: (80%), IR (KBr) (υmax, cm−1): 1760, 1750, 1741, 1635 (C⚌O). Major isomer(Z)-3a (60%), 1H NMR (500.1 MHz, CDCl3): δ 1.19 (6H, t, 3JHH = 6.8 Hz, 2CH3), 3.06 and 3.60 (6H, 2s, 2OCH3), 3.38 (1H, dd, 3JHH = 10.4 Hz, 3JPH = 17.7 Hz, P⚌C–CH), 4.00 and 4.13 (4H, 2m, 2OCH2), 4.63 (1H, d, 3JHH = 10.4 Hz, CH(CO2Et)2), 7.40–7.70 (15Harom, m, 3C6H5). Minor isomer (E)-3a (40%), 1H NMR (500.1 MHz, CDCl3): δ 1.20 (6H, t, 3JHH = 6.8 Hz, 2CH3), 3.50 and 3.71 (6H, 2m, 2OCH3), 3.33 (1H, dd, 3JHH = 10.4 Hz, 3JPH = 18.0 Hz, P⚌C–CH), 3.85 and 3.87 (4H, 2s, 2OCH2), 4.87 (1H, d, 3JHH = 10.8 Hz, CH(CO2Et)2, 7.40–7.70 (15Harom, m, 3C6H5).
2.2.2 Diethyl 2-(2-mercopto-2-thiazoline-3-yl)-3-(triphenylphosphoranylidene)-butanedioate (3p)
White powder, m.p. 111–112 °C, yield: (80%), IR(KBr) (υmax, cm−1): 1750 and 1638 (C⚌O), 1460 (C⚌S). Major isomer(Z)-3p (75%), 1H NMR (500.1 MHz, CDCl3): δ 0.43 and 1.30 (6H, 2t, 3JHH = 7.0 and 7.2 Hz, 2CH3), 3.20 (2H, m, CH2N), 3.49–4.35 (4H, m, 2OCH2), 4.44 (2H, m, CH2S), 5.39 (1H, d, 3JPH = 17.8 Hz, P⚌C–CH), 7.48–7.69 (15Harom, m, 3C6H5). Minor isomer (E)-3p (25%), 1H NMR (500.1 MHz, CDCl3): δ 1.17 and 1.20 (6H, 2t, 3JHH = 7.0 and 7.2 Hz, 2CH3), 3.30 (2H, m, CH2N), 3.49–4.35 (4H, m, 2OCH2), 4.60 (2H, m, CH2S), 5.37 (1H, d, 3JPH = 19.2 Hz, P⚌C–CH), 7.48–7.69 (15Harom, m, 3C6H5).
2.2.3 Diethyl 2-(1,3-dimethylbarbituric acid-5-yl)-3-(triphenylphosphoranylidene)-butane-1,4-dioate (5b)
Colorless crystals, m.p. 154–156 °C, yield: (70%), IR (KBr) (υmax, cm−1): 1713, 1659, 1582 (C⚌O). Major isomer-5b (70%), 1H NMR (500.1 MHz, CDCl3): δ 0.72 (3H, t, 3JHH = 7.3 Hz, CH3), 0.82 (3H, t, 3JHH = 6.9 Hz, CH3), 2.92 (6H, s, 2NCH3), 3.63 and 3.72 (4H, m, 2OCH2), 4.97 (1H, dd, 3JHH = 10.3 Hz, 3JPH = 5.3 Hz, P–CH–CH), 5.79 (1H, dd, 3JHH = 10.3 Hz, 2JPH = 10.8 Hz, P–CH–CH), 7.55–8.05 (15Harom, m, 3C6H5). 13C NMR (125.77 MHz, CDC13): 13.69, 13.96 (2CH3), 27.21 (2NCH3), 43.40 (d, 1JPC = 40.0 Hz, P–CH), 44.49 (d, 2JCP = 4.7 Hz, P–CH–CH), 61.70, 62.44 (2OCH2), 82.60 [d, 3JCP = 11.7 Hz, C(CO)2], 121.65 (d, lJCP = 88.0 Hz, Cipso), 129.70 (d, 3JCP = 12.8 Hz, Cmeta), 134.00 (Cpara), 134.40 (d, 2JCP = 9.0 Hz, Cortho), 153.83 (C⚌O, urea), 162.78 (O⚌C–C–C⚌O), 167.07, 173.99 (2C⚌O, ester). Minor isomer-5b (30%), 1H NMR (500.1 MHz, CDCl3): δ 0.83 (3H, t, 3JHH = 6.7 Hz, CH3), 1.10 (3H, t, 3JHH = 7.0 Hz, CH3), 3.27 (6H, s, 2NCH3), 3.45 and 4.03 (4H, m, 2OCH2), 5.03 (1H, dd, 3JHH = 11.4 Hz, 3JPH = 6.3 Hz, P–CH–CH), 5.89 (1H, dd, 3JHH = 11.4 Hz, 2JPH = 15.4 Hz, P–CH–CH), 7.55–8.05 (15Harom, m, 3C6H5). 13C NMR (125.77 MHz, CDC13): 13.58, 14.40 (2CH3), 27.55 (2NCH3), 41.82 (P–CH–CH), 42.31 (d, 1JPC = 48.6 Hz, P–CH), 61.29, 62.35 (2OCH2), 83.39 [d, 3JCP = 2.3 Hz, C(CO)2], 118.47 (d, lJCP = 86.6 Hz, Cipso), 129.49 (d, 3JCP = 13.0 Hz, Cmeta), 134.40 (d, 2JCP = 7.7 Hz, Cortho), 134.48 (Cpara), 152.90 (C⚌O, urea), 163.08 (O⚌C–C–C⚌O), 167.10, 173.25 (2C⚌O, ester).
2.2.4 Dimethyl 2-(2,2-dimethyl-4,6-dioxo-1,3-dioxane-5-yl)-3-(triphenylphosphoranylidene)-butane-1,4-dioate(5d)
Colorless crystals, m.p. 182–183 °C, yield: (78%), IR (KBr) (υmax, cm−1): 1745, 1735 (C⚌O). Major isomer-5d (80%), 1H NMR (500.1 MHz, CDCl3): δ 1.65 (6H, s, 2CH3), 3.27 and 3.31 (6H, 2s, 2OCH3), 4.79 (1H, dd, 3JHH = 10.7 Hz, 3JPH = 4.4 Hz, P–CH–CH), 5.70 (1H, dd, 3JHH = 10.9 Hz, 2JPH = 11.0 Hz, P–CH–CH), 7.56–8.10 (15Harom, m, 3C6H5). Minor isomer-5d (20%), 1H NMR (500.1 MHz, CDCl3): δ 1.29 (6H, s, 2CH3), 3.29 and 3.55 (6H, 2s, 2OCH3), 4.90 (1H, dd, 3JHH = 11.8 Hz, 3JPH = 3.7 Hz, P–CH–CH), 5.84 (1H, dd, 3JHH = 12.0 Hz, 2JPH = 13.8 Hz, P–CH–CH), 7.56–8.10 (15Harom, m, 3C6H5).
3 Results and discussion
The reaction between triphenylphosphine, acetylenic esters 1 and β-dicarbonyl or heterocyclic compounds (2, 4) leds to the corresponding stable phosphorus ylides 3a–q or 1,4-diionic organophosphorus compounds 5a–f in the presence of sodium dodecyl sulfate as a surfactant in water in good to excellent yields (Schemes 1 and 2).
Synthesis of stable phosphorus ylides 3a–q involving two rotational isomers 3-(Z) and 3-(E) in the presence of sodium dodecyl sulfate in water at room temperature.
Synthesis of 1,4-diionic organophosphorus compound 5a–f in the presence of sodium dodecyl sulfate in water at room temperature.
Based on the well established chemistry of trivalent phosphorus nucleophiles, it is reasonable to assume that phosphorus ylide 3 is formed due to the initial addition of triphenylphosphine to the acetylenic ester 1 and concomitant protonation of 1:1 adduct by the β-dicarbonyl compounds or heterocyclic compounds, such as diethyl malonate, acetyl acetone, 1,3-diphenyl propane-1,3-dione, 2-benzoxazolinone, benzotirazole, and 2-thiazoline-2-thiol) (Scheme 1), whereas 1,4-diionic organophosphorus compound 5 is formed because of the proton shift in initial ylide when β-dicarbonyl compounds such as 1,3-dimethylbarbituric acid, meldrum’s acid, are used as the heterocyclic compounds (Scheme 2). The results are summarized in Tables 1 and 2.
Entry
Z
R
3
Yield%
M.p. (°C)
References
1
Me
3a
80
192–193
Islami et al. (2002)
2
Et
3b
70
165–166
Islami et al. (2002)
3
Me
3c
80
173–175
Islami et al. (2002)
4
Et
3d
70
165–167
Islami et al. (2002)
5
t-Bu
3e
80
145–148
Yavari et al. (2003)
6
Me
3f
80
205–206
Yavari and Islami (1997)
7
Et
3g
78
208–209
Yavari and Islami (1997)
8
t-Bu
3h
80
207–209
Yavari and Islami (1997)
9
Me
3i
85
162–164
Maghsoodlou et al. (2006b)
10
Et
3j
80
184–186
Maghsoodlou et al. (2006b)
11
t-Bu
3k
82
192–194
Maghsoodlou et al. (2006b)
12
Me
3l
88
144–146
Maghsoodlou et al. (2006c)
13
Et
3m
72
148–150
Maghsoodlou et al. (2006c)
14
t-Bu
3n
82
155–157
Maghsoodlou et al. (2006c)
15
Me
3o
80
155–157
Maghsoodlou et al. (2005)
16
Et
3p
75
111–112
Maghsoodlou et al. (2005)
17
t-Bu
3q
80
107–108
Maghsoodlou et al. (2005)
Entry
X
R
5
Yield%
M.p. (°C)
References
1
–CH3N–CO–NCH3–
Me
5a
77
161–163
Yavari et al. (1999)
2
–CH3N–CO–NCH3–
Et
5b
70
155–156
Yavari et al. (1999)
3
–CH3N–CO–NCH3–
t-Bu
5c
82
154–156
Maghsoodlou et al. (2006a)
4
–O–C(CH3)2–O–
Me
5d
78
182–183
Yavari et al. (1999)
5
–O–C(CH3)2–O–
Et
5e
70
163–166
Yavari et al. (1999)
6
–O–C(CH3)2–O–
t-Bu
5f
80
181–183
Yavari et al. (1999)
A comparison of the results obtained from aqueous media with organic solvent media, same phosphorus ylides and 1,4-diionic organophosphorus compounds were synthesized in organic solvents. The results were identical with those that obtained in aqueous media. The spectral data and physical properties of the phosphoranes 3a–q and 1,4-diionic organophosphorus compounds 5a–f were in a good agreement with those that reported in literature (Maghsoodlou et al., 2006a,b,c, 2005; Islami et al., 2002; Yavari et al., 1999, 2003; Yavari and Islami, 1997).
4 Conclusion
For the first time sodium dodecyl sulfate has been employed for a convenient and rapid synthesis of phosphorous ylides and 1,4-diionic organophosphorus compounds in aqueous media. Although, the yields of stable phosphorous ylides or 1,4-diionic organophosphorus compounds are low in comparison with the corresponding products that obtained in the presence of organic solvents, but the reaction times are considerably shorter and also the use of water as a green solvent has some advantages including low cost, non-falmability and its non-toxic.
Acknowledgment
Authors sincerely thank the University of Sistan and Baluchestan for providing financial support of this work.
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