Synthesis of dialkyl 2-(2-oxo-2-phenylethyl)-3-(1,1,1-triphenyl-λ5- phosphanylidene)succinates from triphenylphosphine, acetylenic ester and 4,4,4-trifluoro-1-phenyl-1,3-butanedione in the presence of basic alumina powder

Article abstract of DOI:10.1080/10426500701578431

Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylates, by 4,4,4-trifluoro-1-phenyl-1,3-butanedione leads to vinyltriphenylphosphonium salts, which undergo Michael addi

Full text of DOI:10.1080/10426500701578431

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Synthesis of Dialkyl 2-(2-
Oxo-2-phenylethyl)-3-
(1,1,1-triphenyl-λ5-
phosphanylidene)succinates
from Triphenylphosphine,
Acetylenic Ester and 4,4,4-
Trifluoro-1-phenyl-1,3-
butanedione in the Presence of
Basic Alumina Powder
Ali Jafari a , Ebrahim Ahmadi a , Mokhtar Alinia a
Ali Ramazani a
&
a Department of Chemistry , University of Zanjan ,
Zanjan, Iran
Published online: 09 May 2008.
To cite this article: Ali Jafari , Ebrahim Ahmadi , Mokhtar Alinia & Ali Ramazani
(2008) Synthesis of Dialkyl 2-(2-Oxo-2-phenylethyl)-3-(1,1,1-triphenyl-λ5-
phosphanylidene)succinates from Triphenylphosphine, Acetylenic Ester and 4,4,4-
Trifluoro-1-phenyl-1,3-butanedione in the Presence of Basic Alumina Powder,
Phosphorus, Sulfur, and Silicon and the Related Elements, 183:5, 1116-1123, DOI:
10.1080/10426500701578431
To link to this article: http://dx.doi.org/10.1080/10426500701578431
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Phosphorus, Sulfur, and Silicon, 183:1116–1123, 2008
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500701578431
Synthesis of Dialkyl 2-(2-Oxo-2-phenylethyl)-3-(1,1,1-
triphenyl-λ5-phosphanylidene)succinates from
Triphenylphosphine, Acetylenic Ester and
4,4,4-Trifluoro-1-phenyl-1,3-butanedione in the Presence
of Basic Alumina Powder
Ali Jafari, Ebrahim Ahmadi, Mokhtar Alinia,
and Ali Ramazani
Department of Chemistry, University of Zanjan, Zanjan, Iran
Protonation of the highly reactive 1:1 intermediates, produced in the reaction be-
tween triphenylphosphine and dialkyl acetylenedicarboxylates, by 4,4,4-trifluoro-
1-phenyl-1,3-butanedione leads to vinyltriphenylphosphonium salts, which un-
dergo Michael addition reaction with conjugate base to produce correspond-
ing phosphorus ylides. Basic alumina powder was found to catalyze conversion
5
of the phosphorus ylides to dialkyl 2-(2-oxo-2-phenylethyl)-3-(1,1,1-triphenyl-λ -
phosphanylidene)succinates in solvent-free conditions under microwave (0.9 KW,
3 min) and thermal (25◦C, 120 min) conditions.
Keywords 4,4,4-trifluoro-1-phenyl-1,3-butanedione; acetylenic esters; basic alumina;
michael addition; microwave irradiation; solvent-free conditions; vinyltriphenylphos-
phonium salt
INTRODUCTION
Phosphorus ylides are important reagents in synthetic organic
chemistry,1−16 especially in the synthesis of naturally occurring
products, compounds with biological and pharmacological activity.6
β-Additions of nucleophiles to the vinyl group of vinylic phospho-
nium salts leading to the formation of new alkylidenephosphoranes
has attracted much attention as a very convenient and syntheti-
cally useful method in organic synthesis.18−30 Phosphorus ylides are
a class of special type of zwitterions, which bear strongly nucleophilic
electron rich carbanions. The electron distribution around the P+–
C− bond and its consequent chemical implications had been probed
Received 9 July 2007; accepted 10 July 2007.
This work was supported by the Zanjan University.
Address correspondence to Ali Ramazani, Department of Chemistry, University of
Zanjan, P.O. Box 45195-313, Zanjan, Iran. E-mail: aliramazani@gmail.com
1116

Phosphanylidene)succinates
1117
and assessed through theoretical, spectroscopic and crystallographic
investigations.30 Proton affinity of these ylides can be used as a molec-
ular guide to assess their utility as synthetic reagents and their func-
tion as ligands in coordination and organometallic chemistry.17,30 The
nucleophilicity at the ylidic carbon is a factor of essential mechanistic
importance in the use of these ylides as Wittig reagents.
Waste prevention and environmental protection are major require-
ments in an overcrowded world of increasing demands. Synthetic chem-
istry continues to develop various techniques for obtaining better prod-
ucts with less environmental impact. One of the more promising ap-
proaches is solvent-free organic synthesis.31 In this regard, solvent-
free catalytic organic reaction has received tremendous attention in
recent times.32 We have established a convenient, one-pot method for
preparing stabilized phosphorus ylides utilizing in situ generation of
the phosphonium salts, in the past.18−28 In this article, we report on
the catalytic role of Basic alumina powder in the conversion of phos-
phorus ylides (5) to dialkyl 2-(2-oxo-2-phenylethyl)-3-(1,1,1-triphenyl-
λ5-phosphanylidene)succinates (9) in solvent-free conditions33 under
microwave (0.9 KW, 3 min) and thermal (25◦C, 120 min.) conditions
(Scheme 1).
RESULTS AND DISCUSSION
The phosphorus ylide (5) may result from initial addition of triph-
enylphosphine 1 to the acetylenic ester 2 and concomitant protonation
of the 1:1 adduct by 4,4,4-trifluoro-1-phenyl-1,3-butanedione 3 leads
to vinyltriphenylphosphonium salts 4, which undergo Michael addition
reaction with conjugate base to produce phosphorus ylide (5). TLC indi-
cated formation of ylides 5 in CH2Cl2. Basic alumina powder was found
to catalyze conversion of the phosphorus ylide (5) to dialkyl 2-(2-oxo-
2-phenylethyl)-3-(1,1,1-triphenyl-λ5-phosphanylidene)succinates (9) in
solvent-free conditions33 under microwave (0.9 KW, 3 min) and ther-
mal (25◦C, 120 min.) conditions (Scheme 1). We have also used silica
gel powder in this reaction instead of basic alumina powder, but the
yield of product was very low and several products were observed. The
reaction also was not occurred in dichloromethane solutions after two
days and several others products were observed. We have also used
acetophenone 11 in this reaction instead of 4,4,4-trifluoro-1-phenyl-
1,3-butanedione 3, but the yield of products 9 were very low (Scheme
2).28,34 The weak acidity of acetophenone 11 relative to 4,4,4-trifluoro-
1-phenyl-1,3-butanedione 3 may be the factor in the reduction of yields
(Scheme 2).28,34 The mechanism of the reaction has not been established
experimentally. However, a possible explanation is proposed in Scheme

1118
A. Jafari et al.
SCHEME 1 M = major rotamer; and m = minor rotamer.
1. We have also examined roll of basic alumina powder in the conver-
sion of 4,4,4-trifluoro-1-phenyl-1,3-butanedione 3, to acetophenone 11
(Scheme 3).28,34 Basic alumina powder is able to convert 4,4,4-trifluoro-
1-phenyl-1,3-butanedione 3 to acetophenone 11 in the reaction condi-
tions (Scheme 3).28,34 The structures of the products 9 were deduced
1
from their IR, H NMR, 13C NMR, and 13P NMR spectra (See Experi-
mental section). The NMR spectra indicated that solutions of compound
9 (CDCl3 as solvent) contain two rotamers (9E and 9Z). The relative

Phosphanylidene)succinates
1119
SCHEME 2
SCHEME 3
percentages of rotamers in CDCl3 for each ylide 9 were determined from
the 1H NMR spectra. The IR spectrum of 9a showed strong adsorptions
at 1734 (C O, ester), 1695 (C O, ester), 1634 (C O, ketone) and 1109
(C O, ester) cm−1 indicating the presence of two the ester carbonyls and
the ketone carbonyl functionalities respectively. The 1H NMR spectrum
of 9a (major rotamer (M)) compound exhibited four signals readily rec-
ognized as arising from two OMe groups (δ = 3.09 and 3.66 ppm), CH2
and CH (δ = 3.00–4.00 ppm,m) and aromatic moieties (δ = 7 .26–7.97
1
ppm, m). The H decoupled 13C NMR spectrum of 9a (major rotamer
(M)) showed 16 distinct resonances in agreement with the 9a (major ro-
tamer (M)) structure. Partial assignment of these resonances is given in
the spectral analysis section (See experimental section). The31P NMR
spectrum of 9a (major rotamer (M)) exhibited one signal readily recog-
nized as arising from phosphorus atom of P C group (δ = 2 3.37 ppm).
The 1H, 31P, and 13C NMR signals of compound 9a (minor rotamer (m))
are similar to those of 9a (major rotamer (M)), except for the signal in-
tensities which related to the relative populations of two rotamers of9a
1
in CDCl3 solution (see spectral analysis section). The H, 31P, and 13C
NMR spectra of compound 9b are similar to those of 9a, except for the

1120
A. Jafari et al.
ester groups (1H and 13C NMR), which exhibit characteristic signals
with appropriate chemical shifts (see spectral analysis section).28,34
CONCLUSION
In summary, we have found a new and efficient method for the
preparation of dialkyl 2-(2-oxo-2-phenylethyl)-3-(1,1,1-triphenyl-
λ5-phosphanylidene)succinates (9) from triphenylphosphine (1),
acetylenic ester (2) and 4,4,4-trifluoro-1-phenyl-1,3-butanedione (3)
in the presence of basic alumina powder (Scheme 1). We believe the
reported method offers a simple and efficient route for the prepa-
ration of the stabilized phosphorus ylides 9 (Scheme 1). Its ease
of work up and good yields make it a useful addition to modern
synthetic methodologies.28,34 Other aspects of this process are under
investigation.
EXPERIMENTAL
Melting points were measured on an Electrothermal 9100 apparatus
and are uncorrected. Commercial oven Butane M245 was used for mi-
crowave irradiation. IR spectra were recorded on a FT-IR Mattson 1000
spectrometer. 1H, 31P, and 13C NMR spectra were measured with a
BRUKER DRX-250 AVANCE spectrometer at 250.00, 101.25, and 62.50
MHz, respectively.
General Procedure for the Preparation of Ylides 5 and
Compounds 9a-b
To a magnetically stirred solution of triphenylphosphine 1 (0.262 g, 1
mmol) and 4,4,4-trifluoro-1-phenyl-1,3-butanedione 3 (0.216 g, 1 mmol)
in CH2Cl2 (5 ml) was added dropwise a mixture of 2 (0.13 ml, 1 mmol)
in CH2Cl2 (2 ml) at −10◦C over 15 min. Then 1 g of basic alumina
powder (Merck) was poured into the reaction mixture quickly, and the
mixture was allowed to warm up to room temperature. The solvent
was removed under reduced pressure, and the residue was allowed to
stand for 2 h at room temperature (or under microwave; 0.9 KW, 3 min)
in the solvent-free conditions. The reaction mixture was placed in a
short glassy column. The column was washed using MeOH as eluent.
The solvent was removed under reduced pressure and products were
obtained as white crystals (9a–b) (Scheme 1). The products were re-
crystallized from ethanol. The characterization data of the compounds
(9a–b) are given below.

Phosphanylidene)succinates
1121
Methyl 2-(2-oxo-2-phenylethyl)-3-(1,1,1-triphenyl-λ5-
phosphanylidene)succinate
(9a)
White crystal; m.p.: 196–197◦C; Yield: 56.2% IR (KBr) (νmax, cm−1):
1734 and 1695 (2 C O, Ester); 1634 (C O); 1441 (C C, Aromatic); 1109
(C O); 3061 (C H, Aromatic); 2860 and 2915 (C H, Aliphatic). 1H
NMR (CDCl3) (major rotamer (M) 67% and minor rotamer (m) 33%).
1H NMR (CDCl3) (major rotamer (M)) δ: 3.09 and 3.66 (6 H, 2 s, 2
OMe); 3.00–4.00 (3 H, m, CH2 and CH); 7.26–7.97 (20 H, Aromatic).
13C NMR (CDCl3) (major rotamer (M)) δ: 41.34 (d, 1 J = 122.7 Hz);
PC
2
40.12 (d, J = 12.80 Hz); 40.30 (s); 48.63 and 51.76 (2 OMe); 127.52
PC
1
2
(d, J = 91.3 Hz, Cipso); 128.40 (d, J = 11.8 Hz, Cortho); 131.72 (d,
PC
PC
4 J = 2.5 Hz, Cpara); 131.83 (d, J = 10.0 Hz Cmeta); 128.59 (s, C4);
3
PC
PC
128.41 (s, C3 and C5); 132.58 (s, C2 and C6); 137.75 (s, C1); 169.47 (d,
2 J = 14.0 Hz, CO of ester); 176.23 (d, 3 J = 5.6 Hz, CO of ester);
PC
PC
200.29 (s, CO of ketone).
31P NMR (CDCl3) (major rotamer (M)) δ: 23.37.
1H NMR (CDCl3) (minor rotamer (m)) δ: 3.58 and 3.66 (6 H, 2 s, 2
OMe); 3.00–4.00 (3 H, m, CH2 and CH); 7.26–7.97 (20 H, Aromatic).
13C NMR (CDCl3) (minor rotamer (m)) δ: 42.16 (d, 1 J = 132.9 Hz);
PC
39.29 (d, 2 J = 12.80 Hz); 41.79 (d, 2 J = 1.8 Hz); 50.01 and 51.67 (2
PC
PC
OMe); 126.84 (d, 1 J = 91.3 Hz, Cipso); 137.67 (s, C1); 170.74 (d, 2 J
=
PC
PC
15.6 Hz, CO of ester); 176.32 (d, 3 J = 5.8 Hz, CO of ester); 199.79 (s,
PC
CO of ketone).
31P NMR (CDCl3) (minor rotamer (m)) δ: 23.15.
Ethyl 2-(2-oxo-2-phenylethyl)-3-(1,1,1-triphenyl-λ5-
phosphanylidene)succinate
(9b)
White crystal; m.p.: 150–151◦C; Yield: 49.0% IR (KBr) (νmax, cm−1):
1734 and 1695 (2 C O, Ester); 1626 (C O); 1441 (C C, Aromatic); 1109
(C O); 3061 (C H, Aromatic); 2984 and 2907 (C H, Aliphatic). 1H
NMR (CDCl3) (major rotamer (M) 77% and minor rotamer (m) 23%).
1H NMR (CDCl3) (major rotamer (M)) δ: 0.36 (3 H, t, 3 J = 7.1 Hz,
HH
CH3); 1.53 (3 H, t, 3 J = 7.1 Hz, CH3); 3.00–4.30 (7 H, m, CH2, 2 OCH2
HH
and CH); 7.26–7.99 (20 H, Aromatic).
13C NMR (CDCl3) (major rotamer (M)) δ: 13.91 and 14.25 (2 Me);
41.02 (d, 1 J = 126.3 Hz); 40.23 (d, 2 J = 13.1 Hz); 40.22 (d, 3 J = 4.4
PC
PC
PC
Hz); 57.23 and 60.53 (2 OCH2); 127.53 (d, 1 J = 88.1 Hz, Cipso); 128.33
PC
2
3
(d, J = 11.9 Hz, Cortho); 133.91 (d, J = 9.4 Hz, Cmeta); 131.72 (d,
PC
PC
4 J = 2.5 Hz Cpara); 128.56 (s, C4); 128.42 (s, C3 and C5); 132.60 (s, C2
PC

1122
A. Jafari et al.
and C6); 137.76 (s, C1); 169.21 (d, 2 J = 13.1 Hz, CO of ester); 175.79
PC
(d, 3 J = 5.6 Hz, CO of ester); 200.62 (s, CO of ketone).
PC
31P NMR (CDCl3) (major rotamer (M)) δ: 23.20.
1H NMR (CDCl3) (minor rotamer (m)) δ: 0.36 (3 H, t, 3 J = 7.1 Hz,
HH
CH3); 1.53 (3 H, t, 3 J = 7.1 Hz, CH3); 3.00–4.30 (7 H, m, CH2, 2 OCH2
HH
and CH); 7.26–7.99 (20 H, Aromatic).
13C NMR (CDCl3) (minor rotamer (m)) δ: 18.40 and 15.22 (2 Me);
42.28 (d, 1 J = 133.8 Hz); 39.52 (d, 2 J = 12.9 Hz); 41.74 (d, 3 J = 3.7
PC
PC
PC
Hz); 57.96 and 58.20 (2 OCH2); 126.84 (d, 1 J = 91.3 Hz, Cipso); 128.44
PC
(d, 2 J = 10.6 Hz, Cortho); 133.84 (d, 3 J = 9.4 Hz, Cmeta); 137.68 (s,
PC
PC
2
3
C1); 170.37 (d, J = 18.3 Hz, CO of ester); 175.92 (d, J = 6.9 Hz,
PC
PC
CO of ester); 200.06 (s, CO of ketone).
31P NMR (CDCl3) (minor rotamer (m)) δ: 23.14.
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