H. Mahdavi, J. Amani / Tetrahedron Letters 49 (2008) 2204–2207
2207
1
oxide (APDPPO) was obtained as white crystals in 87% yield,
mp = 166 °C. IR (KBr) (mmax, cmÀ1): 3441 and 3309 (NH2), 1436 (P–
Ph), 1180 (P@O). 1H NMR (500.1 MHz, CDCl3): d 3.89 (2H, s, NH2),
132.70 (2C, d, JPC = 104.83 Hz, Cipso), 132.77–133.65 (1C, d,
1JPC = 110.61 Hz, Cipso), 132.49–132.57 (4C, d, JPC = 10.06 Hz,
Carom,meta to P@O), 132.61–132.63 (2C, d, JPC = 2.64 Hz, Carom,para
to P@O), 134.72 (2C, s, HC@CH), 169.39 (2C, s, C@O). MS (70 eV):
m/z (%) = 372 (M+À1, 33), 344 (7), 277 (100), 199 (39), 183 (32), 152
(22), 77 (40), 51 (26), 43 (22).
3
4
3
4
6.82–6.84 (1H, ddd, JHH = 8.01 Hz, JHH = 1.23 and 1.18 Hz,
CHortho to NH2), 6.90–6.94 (1H, dddd, 3JPH = 11.85 Hz,
4
3JHH = 7.54 Hz, JHH = 1.01 and 0.98 Hz, CHpara to NH2), 7.06–
3
4
7.09 (1H, ddd, JPH = 13.19 Hz, JHH = 1.78 and 1.7 Hz, CHortho to
Preparation of copolymer 1: Copolymer 1 was prepared by the radical
copolymerization of 3-maleimidophenyldiphenylphosphine oxide
(MPDPPO) with styrene. The reaction was carried out in a round-
bottomed flask at 60 °C in dry dioxane under an argon atmosphere.
MPDPPO and styrene monomer were reacted in a 1:1 molar ratio with
2 mol % of AIBN initiator with respect to the combined monomers.
The copolymer was obtained by precipitation from n-hexane. The
resulting copolymer was purified by reprecipitation from dichloro-
methane into n-hexane and dried in vacuo. The composition of the
copolymer was calculated from elemental analysis of phosphorus. The
percentage of phosphorus content in the copolymer was about 5.6%.
IR (KBr) (mmax, cmÀ1): 1710 (–C@O), 1555, 1483 (–C6H5), 1433 (P–
Ph), 1182 (–P@O). 1H NMR spectrum of P(MPDPPO/St) exhibited
3
NH2 and P@O), 7.20–7.22 (1H, ddd, JHH = 8.01 and 7.74 Hz,
4JPH = 3.69 Hz, CHmeta to NH2), 7.44–7.48 (4H, ddd, 4CHarom,meta to
P@O), 7.53–7.55 (2H, ddd, 2CHarom,para to P@O), 7.67–7.72 (4H,
ddd, 4CHarom,ortho to P@O).13C NMR (125.7 MHz, CDCl3): 118.43–
118.52 (1C, d, 3JPC = 10.68 Hz, Cmeta to NH2), 118.77–118.79 (1C, d,
4JPC = 2.76 Hz, Cortho to NH2), 122.22–122.30 (1C, d,
3JPC = 10.06 Hz, C–NH2), 128.79–128.88 (4C, d, JPC = 12.07 Hz,
Carom,ortho to P@O), 129.74–129.86 (1C, d, JPC = 14.08 Hz, Cpara to
NH2), 132.23–132.25 (2C, d, JPC = 2.64 Hz, Carom,para to P@O),
132.48–132.56 (4C, d, JPC = 9.93 Hz, Carom,meta to P@O), 132.72–
2
2
4
3
1
133.54 (2C, d, JPC = 103.83 Hz, Cipso), 133.23–134.05 (1C, d,
1JPC = 103.58 Hz, Cipso), 147.13–147.24 (1C, d, 2JPC = 14.2 Hz, Cortho
to NO2 and P@O). MS (70 eV): m/z (%) = 292 (M+À1, 35), 277 (100),
214 (5), 199 (22), 183 (21), 167 (4), 152 (14), 77 (24), 65 (5), 51 (16).
Procedure for the synthesis of 3-maleimidophenyldiphenylphosphine
oxide (MPDPPO): Maleic anhydride (10.8 g) was dissolved in 100 mL
of acetone and charged into a 500 mL round-bottomed flask under an
argon atmosphere and stirred in an ice bath. A solution of APDPPO
(29.3 g, 0.1 mol) in 500 mL of acetone was then added dropwise over
2 h. The reaction solution was stirred in an ice bath for another 5 h.
Then, 20.4 mL of acetic anhydride and 2.87 g of sodium acetate were
added, the reaction temperature was raised to 60 °C and maintained
at this temperature for 6 h. After being cooled to room temperature,
the reaction mixture was extracted with chloroform, washed with
water until the solution turned neutral, then the solvent was
evaporated. The crude product was purified by column chromato-
graphy (ethyl acetate) and dried. 3-Maleimidophenyldiphenylphos-
phine oxide (MPDPPO) was obtained as a yellowish solid in a 79%
yield. IR (KBr) (mmax, cmÀ1): 3057 (–C@C–H), 1720 (C@O), 1555,
1480 (–C6H5), 1433 (P–Ph), 1188 (–P@O), 831 (C@C). 1H NMR
aromatic protons at around 7.0–7.6 ppm in a very broad fashion. 31
NMR (202.4 MHz, CDCl3): 28.50 (1P, s, P@O).
P
14. Representative experimental procedure for the synthesis of 4-nitro-
benzyl 4-nitrobenzoate: Triflic anhydride (0.13 mL, 0.75 mmol) was
added to a solution of polymer-supported triphenylphosphine oxide 1
(0.55 g, 1 mmol, 1.8 mmol/g) in dry dichloromethane (15 mL) under a
nitrogen atmosphere. A brown precipitate was generated immedi-
ately, which was stirred for 30 min. It was important to distil the triflic
anhydride from a small amount of P2O5 prior to use. 4-Nitrobenzyl
alcohol (0.113 g, 0.74 mmol) was added and the solution stirred at
room temperature for 30 min. 4-Nitrobenzoic acid (0.124 g,
0.74 mmol) and diisopropylethylamine (0.44 mL) were then added
to afford a yellow solution. After stirring for 2 h at room temperature,
the mixture was washed with saturated aqueous NaHCO3 and water.
The solution was then poured into THF to precipitate the copolymer.
Then, the suspension was filtered and the filtrate was concentrated
and purified by flash chromatography (1:1, DCM/hexane) to give the
product as a yellow solid in high yield (96%). Mp 167–168 °C (lit.,17
168 °C).
15. Alvarez, S. G.; Alvarez, M. T. Synthesis 1997, 413.
16. Elson, K. E.; Jenkins, I. D.; Loughlin, W. A. Tetrahedron Lett. 2004,
45, 2491.
17. Lyons, E.; Reid, E. J. Am. Chem. Soc. 1917, 39, 1727.
18. Cline, G. W.; Hanna, S. B. J. Am. Chem. Soc. 1987, 109, 3087.
19. Pitts, M. R.; Harrison, J. R.; Moody, C. J. J. Chem. Soc., Perkin
Trans. 1 2001, 955.
20. Aggarwal, V. K.; Kalomiri, A. P.; Thomas, A. P. Tetrahedron:
Asymmetry 1994, 5, 723.
21. O’Connor, C. J.; Mitha, A. S. H.; Walde, P. Aust. J. Chem. 1986, 39,
249.
3
(500.1 MHz, CDCl3): 6.86 (2H, s, CH@), 7.61 (1H, ddd, JHH = 8.1
4
and 8.0 Hz, JPH = 3.23 Hz, CHmeta to N(COCH)2), 7.66–7.70 (2H,
3
m, CHortho and para to N(COCH)2), 7.76 (1H, ddd, JPH = 12.09 Hz,
4JHH = 1.76 and 1.68 Hz, CHortho to NH2 and N(COCH)2), 7.51 (4H,
ddd, 4CHarom,meta to P@O), 7.58–7.60 (2H, ddd, 2CHarom,para to
P@O), 7.73 (4H, ddd, 4CHarom,ortho to P@O). 13C NMR (125.7 MHz,
2
CDCl3): d 129.02–129.12 (4C, d, JPC = 12.19 Hz, Carom,ortho to
P@O), d 129.06–129.15 (1C, d, 2JPC = 11.94 Hz, Cpara to N(COCH)2),
4
d
129.59–129.61 (1C, d, JPC = 2.64 Hz, Cortho to N(COCH)2),
3
129.70–129.79 (1C, d, JPC = 11.31 Hz, Cmeta to N(COCH)2),
130.21–130.30 (1C, d, JPC = 12.82 Hz, Cortho to N(COCH)2 and
P@O), 131.64–131.72 (1C, d, 3JPC = 9.05 Hz, C–N(COCH)2), 131.86–
2