Triphenylphosphine oxide supported on non-cross-linked maleimide-styrene copolymer: application as a novel Hendrickson reagent

Article abstract of DOI:10.1016/j.tetlet.2008.02.001

A new triphenylphosphine oxide reagent linked to a linear maleimide-styrene copolymer is synthesized. This phosphine-bound copolymer is converted to copolymer-supported triphenylphosphine ditriflate as a novel Hendrickson reagent by treatment with triflic anhydride. This reacts rapidly in various dehydration reactions such as anhydride, ester and amide formation. This linear and soluble support is also easily recovered and recycled several times without loss of efficiency.

Full text of DOI:10.1016/j.tetlet.2008.02.001

Available online at www.sciencedirect.com
Tetrahedron Letters 49 (2008) 2204–2207
Triphenylphosphine oxide supported on non-cross-linked
maleimide–styrene copolymer: application as a novel
Hendrickson reagent
Hossein Mahdavi *, Javad Amani
School of Chemistry, University College of Science, University of Tehran, PO Box 14155-645, Tehran, Iran
Received 27 November 2007; revised 14 January 2008; accepted 1 February 2008
Available online 7 February 2008
Abstract
A new triphenylphosphine oxide reagent linked to a linear maleimide–styrene copolymer is synthesized. This phosphine-bound
copolymer is converted to copolymer-supported triphenylphosphine ditriflate as a novel Hendrickson reagent by treatment with triflic
anhydride. This reacts rapidly in various dehydration reactions such as anhydride, ester and amide formation. This linear and soluble
support is also easily recovered and recycled several times without loss of efficiency.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords: Soluble-supported reagent; Dehydration; Hendrickson reagent; Triphenylphosphine oxide
The Hendrickson reagent,1–5 triphenylphosphonium
anhydride trifluoromethane sulfonate, is a useful reagent
for dehydration reactions such as ester, ether and amide
formation in a manner analogous to the Mitsunobu reac-
tion.6–9 Indeed, an alkoxyphosphonium salt is the key
intermediate in both reactions. The Hendrickson reagent
has the following advantages over Mitsunobu reagents:
(a) the recovered phosphine oxide can be readily recycled
by treatment with trifluoromethanesulfonic (triflic) anhy-
dride; (b) the use of azodicarboxylates is not required
and (c) the alkylation of the hydrazinedicarboxylate and
other side reactions do not occur.
However, one of the main drawbacks of this reagent is
the formation of a double stoichiometric amount of tri-
phenylphosphine oxide. Also, the work-up of the reaction
is sometimes problematic due to the difficulty in completely
removing triphenylphosphine oxide from the reaction
mixture.
Thus a method is required, which would allow easy
removal of triphenylphosphine oxide. One possible solu-
tion is to use a polymer-bound reagent.
The use of polymeric supports in organic synthesis has
become a common practice.10 Insoluble supports such as
lightly cross-linked polystyrene have generally been used
for this purpose. However, despite the well-known advan-
tages of insoluble supports, there are several shortcomings
in the use of these resins because of the heterogeneous
nature of the reaction conditions. Several laboratories have
explored alternative methods to restore homogeneous
reaction conditions resulting from a number of problems
associated with insoluble polymer supports, including
nonlinear kinetic behavior, unequal distribution and/or
access to the chemical reaction, solvation problems associ-
ated with the nature of the support and synthetic difficulties
in transferring standard organic reactions to the solid
phase. Therefore, in recent years, the use of soluble polymer-
supported reagents and catalysts has gained significant
attention as an alternative to traditional solid-phase
synthesis.11,12
*
Corresponding author. Tel.: +98 21 61112725; fax: +98 21 66495291.
In this Letter, we report the synthesis and application of
triphenylphosphine oxide supported on non-cross-linked
E-mail addresses: hmahdavi@khayam.ut.ac.ir, hosinmahdavi@ut.ac.ir
(H. Mahdavi).
0040-4039/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2008.02.001

H. Mahdavi, J. Amani / Tetrahedron Letters 49 (2008) 2204–2207
2205
NH2
NO2
O
P
O
P
O
P
b
a
APDPPO
NPDPPO
c
O
O
O
O
N
N
O
O
O
P
N
O
d
e
P
OSO2CF3
CF3SO2O
P
MPDPPO
1
2
Scheme 1. Reagents and conditions: (a) H2SO4, fuming HNO3, À25 °C; (b) hydrazine hydrate, Pd/C; (c) (1) maleic anhydride, acetone, 0 °C, Ar, 4 h; (2)
CH3COONa, Ac2O, 60 °C, Ar, 6 h; (d) styrene, AIBN, 60 °C, Ar; (e) (CF3SO2)2O, DCM, N2, 0.5 h.
maleimide–styrene copolymer 1 as a novel soluble support
(Scheme 1). This copolymer has a reasonably high loading
and should allow stoichiometric reactions to take place.
Copolymer 1 was synthesized in four steps from tri-
phenylphosphine oxide.13 3-Nitrophenyldiphenylphosphine
oxide (NPDPPO) was synthesized by nitration of triphen-
ylphosphine oxide. A subsequent reduction of NPDPPO
with hydrazine hydrate led to the 3-aminophenyldiphenyl-
phosphine oxide (APDPPO). In the next step, 3-male-
imidophenyldiphenylphosphine oxide (MPDPPO) was
prepared by the reaction of APDPPO with maleic anhy-
dride. MPDPPO was readily copolymerized with styrene
in the presence of 2,2’-azobisisobutyronitrile (AIBN) as a
radical initiator to provide copolymer 1. Next, the phos-
phine oxide reagent 1 was treated with triflic anhydride
in dry dichloromethane to produce a non-cross-linked
polymer-supported triphenylphosphine ditriflate 2.
oxide byproduct was accomplished by a simple precipita-
tion and filtration procedure.14
A preparative-scale procedure involved successive addi-
tion of 4-nitrobenzyl alcohol, 4-nitrobenzoic acid and
diisopropylethylamine to a mixture of 2 in DCM to gener-
ate a homogeneous solution. Isolation of the product, 4-
nitrobenzyl 4-nitrobenzoate, was accomplished by washing
the reaction mixture with sodium hydrogen carbonate to
remove the diisopropylethylammonium triflate. The poly-
meric triphenylphosphine oxide precipitated upon the addi-
tion of tetrahydrofuran (THF). Then, the polymer
suspension was filtered and the filtrate was concentrated
and purified by flash chromatography (1:1, DCM/hexane)
to afford the product as a yellow solid in high yield (96%)
(Table 1). Also, the 31P NMR spectrum of the crude
product showed no signal, meaning that the polymeric
triphenylphosphine oxide was precipitated and removed
completely.
It was imperative to employ a small excess of 1 to ensure
that all of the triflic anhydride was consumed as excess
triflic anhydride could react with the substrate to form its
corresponding anhydride. Polymer-supported triphenyl-
phosphine ditriflate 2 was subsequently used in a series of
dehydration reactions. Removal of the triphenylphosphine
Treatment of 2 with 4-nitrobenzoic acid, benzylamine
and diisopropylethylamine gave N-benzyl 4-nitrobenz-
amide in 97% yield. The filtered polymeric catalyst could
be recovered several times and used without any loss in
its reactivity.
Table 1
Dehydration reactions with phosphine polymer 2
Entrya,b
Substrate
Nucleophile
Product
Yielde (%)
Mp °C (lit. mp °C)
1
2
3
4
5
6
7
8
a
4-NO2–C6H4CH2OH
4-NO2–C6H4COOH
4-CH3–C6H4COOH
4-Cl–C6H4CH2OH
4-NO2–C6H4CH2OH
meso-C6H5CH(OH)CH(OH)C6H5
4-Cl–C6H4CH2OH
4-NO2–C6H4COOH
C6H5CH2NH2
4-CH3–C6H4COOH
CH3–C(O)–SH
4-MeO–C6H4OH
—
4-Nitrobenzyl 4-nitrobenzoate
N-Benzyl 4-nitrobenzamide
4-Toluic anhydride
4-Chlorobenzyl thioacetate
o-(4-Nitrobenzyl)-4-methoxyphenol
(E)-Stilbene oxide
96
97
94
92
90
87
90
83
167–168 (168)17
142 (141–143)18
93–95 (93)3
Oil5
87 (88)19
64–65 (65–67)20
Oil5
47–49 (48)21
c
NaN3
4-NO2–C6H4COOHd
4-Chlorobenzyl azide
Cyclohexyl 4-nitrobenzoate
Cyclohexanol
Reaction conditions: 2 (1.35 equiv), triflic anhydride (1.0 equiv), nucleophile (1.0 equiv), diisopropylethylamine (3.5 equiv), DCM (10 mL).
Reaction times: entries 1, 4 (2 h, rt); entries 2, 3, 5–7 (overnight, rt); entry 8 (overnight, reflux).
Added as a 0.5 M solution in DMSO.
Active ester generated using DMAP (1.0 equiv).
Isolated yield.
b
c
d
e

2206
H. Mahdavi, J. Amani / Tetrahedron Letters 49 (2008) 2204–2207
In a similar fashion, 4-toluic anhydride was formed in
References and notes
high yield (94%), from the reaction of 2 equiv of 4-toluic
acid with 2 and diisopropylethylamine in DCM. Treatment
of 2 with 4-chlorobenzyl alcohol, thioacetic acid and diiso-
propylethylamine in DCM produced 4-chlorobenzyl thio-
acetate, which was purified by flash chromatography (1:1,
DCM/hexane). Addition of 4-methoxyphenol and diiso-
propylethylamine to a mixture of 4-nitrobenzyl alcohol
and 2 in DCM gave o-(4-nitrobenzyl)-4-methoxyphenol
in high yield (90%). In another reaction, (E)-stilbene oxide
was synthesized by the treatment of 2 with meso-hydro-
benzoin in the presence of diisopropylethylamine (87%
yield). We also synthesized 4-chlorobenzyl azide from its
corresponding alcohol (4-chlorobenzyl alcohol) using a
0.5 M solution of NaN3 in DMSO15 and diisopropylethyl-
amine, in high yield (90%) (1:1, DCM/hexane).
1. Hendrickson, J. B. In Encyclopedia of Reagents for Organic Synthesis;
Paquette, L. A., Ed.; Wiley, 1995; Vol. 8, pp 5405–5407.
2. Hendrickson, J. B.; Hussoin, M. S. J. Org. Chem. 1987, 52,
4137.
3. Hendrickson, J. B.; Hussoin, M. S. J. Org. Chem. 1989, 54, 1144.
4. Hendrickson, J. B.; Hussoin, M. S. Synlett 1990, 423.
5. Elson, K. E.; Jenkins, I. D.; Loughlin, W. A. Org. Biomol. Chem.
2003, 1, 2958.
6. Mitsunobu, O. Synthesis 1981, 1.
7. Hughes, D. L. Org. React. 1992, 42, 335.
8. Jenkins, I. D.; Mitsunobu, O. In Encyclopedia of Reagents for Organic
Synthesis; Paquette, L. A., Ed.; Wiley, 1995; Vol. 8, pp 5379–5390.
9. Hughes, D. L. Org. Prep. Proced. Int. 1996, 28, 127.
10. Polymeric Materials in Organic Synthesis and Catalysis; Chael, M.;
Buchmeiser, R., Eds.; Wiley, 2003.
11. Shuttleworth, S. J.; Allin, S. M. Synthesis 2000, 1035.
12. Ley, S. V.; Baxendale, I. R.; Bream, R. N. J. Chem. Soc., Perkin
Trans. 1 2000, 3815.
An additional advantage of polymeric reagent 2 is that
after the reaction, it is obtained as a triphenylphosphine
oxide copolymer, which is readily reconverted to 2 by treat-
ment with triflic anhydride. The recovered copolymer can
be recycled at least four times without the loss of its
efficiency.
13. Procedure for the synthesis of 3-nitrophenyldiphenylphosphine oxide
(NPDPPO): Triphenylphosphine oxide (27.8 g, 0.1 mol) was charged
into a 500 mL round-bottomed flask equipped with an overhead
mechanical stirrer and an addition funnel and 100 mL of 98% sulfuric
acid was added. The reaction system was cooled to À25 °C. Then a
solution of 4.1 mL (0.1 mol) of fuming nitric acid in 25 mL of sulfuric
acid was cooled to 0 °C and transferred to the addition funnel. The
acid mixture was slowly added dropwise and the bath temperature
was maintained at À25 °C. The reaction was allowed to continue for
2 h at À10 °C, 3 h at À5 °C, 3 h at 0 °C and 3 h at room temperature,
respectively, once the addition had been completed. The reaction
mixture was poured slowly onto ice. The precipitate produced was
dissolved in chloroform, washed with aqueous sodium bicarbonate
solution and water until the solution turned neutral. The solvent was
removed, and the resulting crude product was recrystallized from
cyclohexane. 3-Nitrophenyldiphenylphosphine oxide (NPDPPO) was
obtained as white crystals in a yield of 75%, mp = 91 °C. IR (KBr)
(mmax, cmÀ1): 879 (–C–NO2), 1190 (P@O), 1348 and 1523 (Ph–NO2)
and 1438 (P–Ph). 1H NMR (500.1 MHz, CDCl3): d 7.50 (1H, ddd,
In conclusion, we have generated a soluble triphenyl-
phosphine oxide supported on non-cross-linked malei-
mide–styrene copolymer 1 as a stoichiometric reagent for
several chemical reactions. Copolymer 1 reacts rapidly with
triflic anhydride and produces polymer-supported triphen-
ylphosphine ditriflate 2 as a novel dehydrating reagent.
The use of new polymeric reagent 2 offers considerable
advantages over triphenylphosphonium anhydride triflate
as the main by-product, triphenylphosphine oxide, remains
attached to the polymer-support and is removed by simple
filtration after precipitation, so no chromatography is nec-
essary to remove this side-product. Furthermore, an excess
of the reagent can be used without subsequent problems
during purification. On comparison with the heterogeneous
reaction,16 product yields are equivalent but reaction times
are shorter.
4
3JHH = 8.2 and 8.1 Hz, JPH = 2.9 Hz, CHmeta to NO2), 7.56 (4H,
ddd, 4CHarom,meta to P@O), 7.64 (2H, ddd, 2CHarom,para to P@O),
7.70–7.73 (4H, ddd, 4CHarom,ortho to P@O), 8.11–8.15 (1H, dddd,
3
4
3JPH = 11.0 Hz, JHH = 7.6 Hz, JHH = 1.03 and 1.01 Hz, CHpara to
3
4
NO2), 8.42–8.44 (1H, ddd, JHH = 8.2 Hz, JHH = 1.1 and 1.07 Hz,
CHortho to NO2), 8.50–8.53 (1H, ddd, JPH = 11.96 Hz, JHH = 1.75
and 1.6 Hz, CHortho to NO2 and P@O). 13C NMR (125.7 MHz,
CDCl3): 127.11–127.20 (1C, d, JPC = 11.8 Hz, Cmeta to NO2),
128.87–128.97 (1C, d, JPC = 12.3 Hz, Cpara to NO2), 129.28–129.38
3
4
We are currently testing copolymer 1 in other phos-
phine-mediated processes, and the results will be reported
in due course.
3
2
2
(4C, d, JPC = 12.44 Hz, Carom,ortho to P@O), 130.25–130.35 (1C, d,
2JPC = 11.94 Hz, Cortho to NO2 and P@O), 131.15–131.99 (2C, d,
1JPC = 105.59 Hz, 2Cipso), 132.33–132.35 (1C, d, JPC = 2.64 Hz,
4
Acknowledgement
3
Cortho to NO2), 132.40–132.48 (4C, d, JPC = 10.18 Hz, Carom,meta to
P@O), 133.05–133.07 (2C, d, JPC = 2.76 Hz, Carom,para to P@O),
135.96–136.76 (1C, d, JPC = 100.8 Hz, Cipso), 138.15–138.22 (1C, d,
3JPC = 9.17 Hz, C–NO2).
4
We are thankful to the Research Council of the Univer-
sity of Tehran.
1
Procedure for the synthesis of 3-aminophenyldiphenylphosphine
oxide (APDPPO): NPDPPO (32.3 g, 0.1 mol) was charged into a
500 mL round-bottomed flask equipped with an addition funnel and a
reflux condenser. Ethanol (350 mL) and 1.4 g of palladium on
activated carbon (10%) were added. The mixture was warmed to
about 50 °C and while being mechanically stirred, a solution of
hydrazine hydrate (20.5 mL) in ethanol (20 mL) was added dropwise
over 1.5 h while maintaining the temperature at about 50 °C. Then,
the reaction mixture was refluxed for 3 h. The completion of the
reduction was demonstrated by TLC. The reaction mixture was
filtered and the solvent was evaporated. The solid residue was
recrystallized from 2-propanol. 3-Aminophenyldiphenylphosphine
Supplementary data
1H NMR and 13C NMR spectra of 3-nitrophenyldi-
phenylphosphine oxide, 3-aminophenyldiphenylphosphine
oxide and 3-maleimidophenyldiphenylphosphine oxide
and the 31P NMR spectrum of polymer-supported triphen-
ylphosphine oxide are available. Supplementary data asso-
ciated with this article can be found, in the online version,
at doi:10.1016/j.tetlet.2008.02.001.

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