Silica gel catalyzed conversion of dialkyl 2-(2-hydroxy-1-naphthyl)-3-(1,1,1-triphenyl-λ5-phosphanylidene) succinates to alkyl 3-oxo-3H-benzo[f]chromene-1-carboxylates in solvent-free conditions

Article abstract of DOI:10.1080/10426500307901

Protonation of the highly reactive 1:1 intermediates produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylates by 2-hydroxynaphthalene leads to vinyltriphenylphosphonium salts, which undergo aromatic electrophilic substitutio

Full text of DOI:10.1080/10426500307901

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Phosphorus, Sulfur, and Silicon and the Related
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Silica Gel Catalyzed Conversion of Dialkyl 2-(2-
Hydroxy-1-naphthyl)-3-(1,1,1-triphenyl-λ 5 -
phosphanylidene) Succinates to Alkyl 3-Oxo-3 H -
benzo[ f ]chromene-1-carboxylates in Solvent-free
Conditions
Ali Ramazani a & Ali Souldozi a
a Zanjan University , Zanjan, Iran
Published online: 27 Oct 2010.
To cite this article: Ali Ramazani & Ali Souldozi (2003) Silica Gel Catalyzed Conversion of Dialkyl 2-(2-Hydroxy-1-naphthyl)-3-
(1,1,1-triphenyl-λ 5 -phosphanylidene) Succinates to Alkyl 3-Oxo-3 H -benzo[ f ]chromene-1-carboxylates in Solvent-free
Conditions, Phosphorus, Sulfur, and Silicon and the Related Elements, 178:6, 1329-1332, DOI: 10.1080/10426500307901
To link to this article: http://dx.doi.org/10.1080/10426500307901
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Phosphorus, Sulfur, and Silicon, 178:1329–1332, 2003
C
Copyright Taylor & Francis Inc.
ISSN: 1042-6507 print
DOI: 10.1080/10426500390200639
SILICA GEL CATALYZED CONVERSION
OF DIALKYL 2-(2-HYDROXY-1-NAPHTHYL)-3-(1,1,1-
TRIPHENYL- 5-PHOSPHANYLIDENE) SUCCINATES
TO ALKYL 3-OXO-3H-BENZO[ f ]CHROMENE-1-
CARBOXYLATES IN SOLVENT-FREE CONDITIONS
Ali Ramazani and Ali Souldozi
Zanjan University, Zanjan, Iran
(Received November 19, 2002)
Protonation of the highly reactive 1:1 intermediates produced in
the reaction between triphenylphosphine and dialkyl acetylenedi-
carboxylates by 2-hydroxynaphthalene leads to vinyltriphenylphos-
phonium salts, which undergo aromatic electrophilic substitution
reaction with conjugate base to produce dialkyl 2-(1-hydroxy-2-
naphthyl)-3-(1,1,1-triphenyl- 5-phosphanylidene) succinates. Silica gel
was found to catalyze conversion of dialkyl 2-(1-hydroxy-2-naphthyl)-
3-(1,1,1-triphenyl- 5-phosphanylidene) succinates to alkyl 3-oxo-3H-
benzo[ f ]chromene-1-carboxylates in solvent-free conditions at 60 C in
fairly good yields.
Keywords: Acetylenic esters; 2-hydroxynaphthalene; silica gel;
triphenylphosphine; vinyltriphenylphosphonium salt
Chromene skeleton compounds occupy an important place in the
realm of natural and synthetic organic chemistry. They are used as
anticoagulants, additives in food and cosmetics, and in the preparation
of insecticides, optical brighteners, and dispersed fluorescent and
laser dyes.1 Silica gel as an additive promotes the Wittig reactions
of phosphorus ylides with aldehydes, including sterically hindered
aldehydes to increase the rate and yields of alkenes.2,3 In the past
we have established a convenient, one-pot method for preparing
stabilized phosphorus ylides utilizing in situ generation of the phos-
phonium salts.4–9 In this article, we report on the catalytic activity
of silica gel powder in the conversion of dialkyl 2-(1-hydroxy-2-
naphthyl)-3-(1,1,1-triphenyl- 5-phosphanylidene) succinates to alkyl
This work was supported by the Zanjan University Research Council (ZURC4950).
Address correspondence to Ali Ramazani, Chemistry Department, PO Box 45195-313,
Zanjan University, Zanjan, Iran. E-mail: a-ramazani@mail.znu.ac.ir
1329

1330
A. Ramazani and A. Souldozi
SCHEME 1
3-oxo-3H-benzo[ f ]chromene-1-carboxylates in solvent-free condi-
tions9,10 at 60 C in fairly good yields (Scheme 1).
RESULTS AND DISCUSSION
The ylide (5) may result from initial addition of triphenylphosphine 1
to the acetylenic ester 2 and concomitant protonation of the 1:1 adduct,
followed by the electrophilic attack of the vinyltriphenylphosphonium
cation on the aromatic ring at ortho -position relative to the strong acti-
vating group (Scheme 1). TLC indicated formation of ylides 5 in CH2Cl2.
Silica gel powder was found to catalyze conversion of ylides 5
to alkyl 3-oxo-3H-benzo[ f ]chromene-1-carboxylates (6a–b) in solvent-
free conditions9,10 at 60 C in fairly good yields (Scheme 1). TLC
indicated that the reaction was completed after 1 h. In the absence
of silica gel powder, this reaction was completed (6a) at reflux tem-
perature (CH2Cl2 as solvent) after 120 h.11 The structures 6a–b were
deduced from their 1H NMR and 13C NMR spectra and via x-ray single
crystal (for 6a) structure determination (Figure 1).12
In summary, we have found that silica gel powder is able to catalyze
conversion of ylides 5 to compounds 6 in solvent-free conditions. Other
aspects of this process are under investigation.
EXPERIMENTAL
Melting points were measured on an Electrothermal 9100 apparatus
and are uncorrected. 1H and 13C NMR spectra were measured with a
Bruker DRX-500 Avance spectrometer at 500 and125 MHz respectively.

Silica Gel Catalyzed Conversion of Dialkyl
1331
FIGURE 1 ORTEP drawing of 6a.
General Procedure for the Preparation of Ylides 5
and Compounds 6a–b
To a magnetically stirred solution of triphenylphosphine 1 (0.524 g,
2 mmol) and 2-hydroxynaphthalene 3 (0.288 g, 2 mmol) inCH2Cl2 (8 ml)
was added dropwise a mixture of 2 (2 mmol) in CH2Cl2 (6 ml) at 10 C
over 15 min. The mixture was allowed to warm to room temperature.
Silica gel powder (2 g) was added and the solvent was evaporated. Dry
silica gel and the residue were heated for 1 h at 60 C and then placed
over a column of silica gel (10 g). The column chromatography was
washed using ethyl acetate-light petroleum ether (1:10) as eluent. The
solvent was removed under reduced pressure and the products were
obtained as reddish crystals (6a–b). The characterization data of the
compounds (6a–b) are given below.
Methylt 3-oxo-3H-benzo[f]chromene-1-carboxylate (6a)
Reddish crystals, m.p. 138.2–138.8 C; Yield: 56%. 1H NMR
(CDCl3) H: 4.08 (3H, s, OCH3), 6.60 (1H, s, vinylic), 7.48 (1H, d, 3 J
=
HH

1332
A. Ramazani and A. Souldozi
9.0 Hz, arom.), 7.5–7.7 (2H, m, 2CH, arom.), 7.78 (1H, d, 3 J = 8.4 Hz,
arom.), 7.92 (1H, d, 3 J = 7.8 Hz, arom.), 8.03 (1H, d, 3 J HH= 9.0 Hz).
HH
HH
13C NMR (CDCl3) C: 53.58 (CH3), 115.62, 117.41, 123.32, 126.16,
128.20, 129.51, and 134.62 (7 CH), 110.12, 128.05, 130.96 and 145.93
(4C), 154.96 (C–O), 159.51 and 167.82 (2C=O , ester).
Ethyl 3-oxo-3H-benzo[f]chromene-1-carboxylate (6b)
Reddish crystals, m.p. 135.9–136.4 C; Yield: 60%. 1H NMR
(CDCl3) H: 1.43 (3H, t, 3 J = 7.1 Hz, CH3 of Et); 4.56 (2 H, q, 3 J
=
HH
HH
7.1 Hz, OCH2 of Et); 6.59 (1H, s, vinylic), 7.48 (1H, d, 3 J = 9.0 Hz,
HH
arom.), 7.5–7.7 (2H, m, 2CH, arom.), 7.86 (1H, d, 3 J = 8.4 Hz, arom.),
HH
7.92 (1H, d, 3 J = 7.8 Hz, arom.), 8.03 (1H, d, 3 J = 9.0 Hz). 13C NMR
HH
HH
(CDCl3)
:
13C NMR (CDCl3) C: 13.96 (CH3 of Et); 63.06 (OCH2);
C
115.48, 117.37, 123.56, 126.10, 128.00, 129.42, and 134.52 (7 CH),
110.11, 128.02, 130.91 and 146.33 (4C), 154.91 (C–O), 159.58 and 167.34
(2C=O , ester).
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