Chemistry of phosphorus ylides. Part 34 : Synthesis of chromenone phosphanylidene and cyclobutylidene derivatives

Article abstract of DOI:10.1080/10426507.2011.600741

The reaction of nucleophilic phosphacumulene ylides with visnaginone and khellinone afforded the corresponding phosphanylidene and furochromene derivatives. Moreover, pyranochromenes were obtained from the reaction of chromene carbaldehydes with phosphacumulenes. On the other hand, the phosphanylidene-cyclobutylidenes and their dimers were produced from the reaction of furochromene carbaldehydes with the same phosphonium reagents.

Full text of DOI:10.1080/10426507.2011.600741

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Chemistry of Phosphorus Ylides.
Part 34 Synthesis of Chromenone
Phosphanylidene and Cyclobutylidene
Derivatives
Soher S. Maigali a , Mohamed H. Arief b , Marwa EL-Hussieny a &
Fouad M. Soliman a
a Department of Organometallic and Organometalloid Chemistry ,
National Research Center , Dokki , Cairo , Egypt
b Department of Organic Chemistry, Faculty of Science , Banha
University , Banha , Egypt
Published online: 05 Jan 2012.
To cite this article: Soher S. Maigali , Mohamed H. Arief , Marwa EL-Hussieny & Fouad M. Soliman
(2012) Chemistry of Phosphorus Ylides. Part 34 Synthesis of Chromenone Phosphanylidene and
Cyclobutylidene Derivatives, Phosphorus, Sulfur, and Silicon and the Related Elements, 187:2,
190-204, DOI: 10.1080/10426507.2011.600741
To link to this article: http://dx.doi.org/10.1080/10426507.2011.600741
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Phosphorus, Sulfur, and Silicon, 187:190–204, 2012
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2011.600741
CHEMISTRY OF PHOSPHORUS YLIDES, PART 34:
SYNTHESIS OF CHROMENONE PHOSPHANYLIDENE
AND CYCLOBUTYLIDENE DERIVATIVES
Soher S. Maigali,1 Mohamed H. Arief,2 Marwa EL-Hussieny,1
and Fouad M. Soliman1
1Department of Organometallic and Organometalloid Chemistry, National
Research Center, Dokki, Cairo, Egypt
2Department of Organic Chemistry, Faculty of Science, Banha University,
Banha, Egypt
GRAPHICAL ABSTRACT
Abstract The reaction of nucleophilic phosphacumulene ylides with visnaginone and khelli-
none afforded the corresponding phosphanylidene and furochromene derivatives. Moreover,
pyranochromenes were obtained from the reaction of chromene carbaldehydes with phos-
phacumulenes. On the other hand, the phosphanylidene-cyclobutylidenes and their dimers
were produced from the reaction of furochromene carbaldehydes with the same phosphonium
reagents.
Keywords Cyclobutylidenes; furochromenes; Phosphacumulene ylides; phosphanylidenes;
pyranochromenes
INTRODUCTION
Visnagin and khellin are natural linear furochromenes that can be isolated from
Ammi visnaga L.,1 which are perennial herbaceous plants that grow wild in many Eastern
Received 12 April 2011; accepted 10 June 2011.
Address correspondence to Fouad M. Soliman, Department of Organometallic and Organometalloid Chem-
istry, National Research Center, El-Behoos St., P. O. 12622, Dokki, Cairo, Egypt. E-mail: solimanfma2@
yahoo.com
190

CHROMENONE PHOSPHANYLIDENE AND CYCLOBUTYLIDENE DERIVATIVES
191
Mediterranean countries.2 They have antispasmodic properties and are used in the treat-
ment of angina pectoris.3 Moreover, the anticancer activities of these naturally occurring
furochromones have been reported.4,5 On the basis of these findings, the present work was
aimed to synthesize a new group of furochromones incorporating different heterocycle, car-
bocycle, and phosphorane moieties. We expected the resulting compounds to have higher
activities and lower side effects acting as antitumor agents.
RESULTS AND DISCUSSION
Owing to our interest in the synthesis of analogues of naturally occurring com-
pounds containing phosphorane, heterocyclic, and carbocyclic moieties,6–10 we investi-
gated the reaction of active nucleophilic phosphacumulene ylides with benzofuranes and
chromones. The benzofuranes 1-(6-hydroxy-4-methoxybenzofuran-5-yl) ethanone (vis-
naginone) (2a) and 1-(6-hydroxy-4,7-dimethoxybenzofuran-5-yl) ethanone (khellinone)
(2b) were obtained by aqueous alkaline hydrolysis of visnagin (1a) and khellin (1b), re-
spectively.11 We have found that the reaction of visnaginone (2a) with one equivalent of (N-
phenyliminovinylidene)triphenylphosphorane (3) proceeds in dry tetrahydrofuran (THF)
at room temperature for 8 h to give N-(4-methoxy-5-methyl-7H-furo[3,2-g]chromen-7-
ylidene)benzenamine (5a) together with triphenylphosphine oxide (TPPO). Carrying out
the same reaction using two equivalents of the active phosphacumulene 3 led to the forma-
tion of the same product 5a. The phosphacumulene 3 is added to the phenolic OH group
rather than the acetyl carbonyl group of 2a to give first the intermediate ylide 4a, which
cyclizes by intramolecular Wittig reaction with the formation of the furochromeneylidene
5a along with TPPO. The structure of compound 5a was established on the basis of IR,
1H, 13C NMR, and mass spectral data. The mass spectrum of compound 5a showed the
1
molecular ion peak at m/z = 305 (M+, 35.5%). The H NMR spectrum of 5a showed
signals at δ = 2.55 (CH3) as a doublet (JHH = 2.5 Hz) due to allylic coupling with the
vinyl proton at C-6, which appeared at δ = 6.09. The NMR signal for the OCH3 protons
was found at δ = 4.09, and the furan ring protons gave two doublets (each with JHH
=
2.30 Hz) at δ = 6.98 (3-H) and at δ = 7.57 (2-H). The signal at δ = 7.14 was attributed to
the proton at C-9. Khellinone (2b) was found to react with phosphorane 3 in THF at room
temperature during 10 h to give TPPO alongwith a mixture of two products, compounds 5b
and 8b. The first main product was identified as N-(4,9-dimethoxy-5-methyl-7H-furo[3,2-
g]chromen-7-ylidene) benzenamine (5b), and the second minor product was identified as
4,9-dimethoxy-5-methyl-7H-furo[3,2-g]chromen-7-one (8b). Compound 8b was obtained
by partial hydrolysis of 5b. When compound 5b was boiled in toluene for 3 h, compound
8b and traces of 5b were isolated (Scheme 1).
The reaction of (2-oxovinylidene)triphenylphosphorane (6) with 2a and 2b was also
investigated. We have found that the reaction proceeds in THF at room temperature and is
complete within 8 h in the case of 2a and within 12 h in the case of 2b to give (triphenyl-λ5-
phosphanylidene)acetic acid 5-acetyl-4-methoxy-benzofuran-6-yl ester (7a) and (triphenyl-
λ5-phosphanylidene)acetic acid 5-acetyl-4,7-dimethoxybenzofuran-6-yl ester (7b), respec-
tively. The phosphanylidene 7a shows a peak in the mass spectrum at m/z = 508 (M+,
25.3%) and a signal in the 31P NMR spectrum at δ = 17.4 ppm, which supports a phospho-
rane structure.12–14 When the phosphoranes 7a and 7b are boiled in toluene, intramolecular
Wittig reaction occurs with the formation of 4-methoxy-5-methyl-7H-furo[3,2-g]chromen-
7-one (8a) and 4,9-dimethoxy-5-methyl-7H-furo[3,2-g]chromen-7-one (8b), respectively,
together with TPPO. It was reported15 that the reaction of a stabilized phosphonium ylide,

192
S. S. MAIGALI ET AL.
O
C
OCH3
O
O
OCH3
CH3
KOH
H2O
(C6H5)3P
C C N C6H5
3
O
OH
CH3
O
in THF, at room temp.
R
R
2a, R= H
b, R = OCH3
1a, R= H
b, R = OCH3
CH3
CH3
OCH3
CH3
OCH3
OCH3
C
O
HC
OCH3
P(C6H5)3
- (C6H5)3P
O
+
C
O
O
O
N
C6H5
O
N
C6H5
O
O
O
R
R
4a, R= H
b, R = OCH3
8b
5a, R= H
b, R = OCH3
Scheme 1
carbmethoxymethylenetriphenylphosphorane (9), with compounds 2a and 2b affords the
chromenones 8a and 8b, respectively. In this case the stabilized phosphonium ylide 9 reacts
with the acetyl carbonyl group rather than with the OH group to give the intermediate com-
pounds 10a,b, which are lactonized to give compounds 8a,b with elimination of methanol
(Scheme 2).
CH3
OCH3
C
O
P(C6H5)3
O
(C6H5)3P
C
C
O
HC
- (C6H5)3P = O
Toluene
6
C
O
O
in THF, at room temp.
R
7a, R= H
b, R = OCH3
CH3
OCH3
2a,b
O
O
O
R
8a, R= H
b, R = OCH3
O
CH3
C
OCH3
(C6H5)3P
C
H
C
OCH3
CH
9
- CH3OH
C
O
in toluene
O
OH
OCH3
R
10a, R= H
b, R = OCH3
Scheme 2

CHROMENONE PHOSPHANYLIDENE AND CYCLOBUTYLIDENE DERIVATIVES
193
We have studied the reaction of the active phosphacumulenes 3 and 6 with 1-(6-
hydroxy-4-methoxybenzofuran-5-yl)-3-phenylprop-2-en-1-one (11a) and 1-(6-hydroxy-
4,7-dimethoxybenzofuran-5-yl)-3-phenylprop-2-en-1-one (11b) in boiling toluene. The re-
action completes within 5 h in case of 3 and within 8 h in case of 6. The corresponding
chromenes 13a–d were obtained together with TPPO. Formation of compounds 13a–d can
be explained by the addition of the phenolic OH group of 11a,b to the phosphacumulenes
3 and 6 to give first the intermediate phosphonium ylides 12a–d, which are then cyclized to
the chromenes 13a–d with formation of TPPO. The IR and 1H NMR spectra of compounds
13a–d indicate the absence of the phenolic OH groups, which appear in the 1H NMR spectra
of the starting materials at δ = 12.69 (11a) and at δ = 12.70 (11b). Furthermore the 1H NMR
spectrum of 13a shows the signals of the two protons of the styryl group as two doublets
centered at δ = 6.74 and 7.75 (JHH = 16.1 Hz), which exclude a [4+2]-cycloaddition and
the formation of a pyran structure.
The reaction of 1-(6-hydroxy-4-methoxy-benzofuran-5-yl)ethanone oxime (14a) and
1-(6-hydroxy-4,7-dimethoxy-benzofuran-5-yl)ethanone oxime (14b) with the phosphacu-
mulenes 3 and 6 was also investigated. Compounds 14a and 14b were prepared from
the reaction of benzofuran ethanones 2a,b with hydroxylamine hydrochloride.16 When
compounds 14a,b were allowed to react with the phosphoranes 3 and 6 in THF at
room temperature for 5 h, 4-methoxy-3-methyl-furo[2ꢁ,3ꢁ:4,5]benzo[1,2-d]isoxazole (15a)
and 4,8-dimethoxy-3-methyl-furo[2ꢁ,3ꢁ:4,5]-benzo[1,2-d]isoxazole (15b) were obtained,
respectively. In this case, cyclization occurred with the formation of the isoxazole ring and
no reaction was observed between compounds 14a,b and the phosphorus reagents 3 and 6.
The IR and 1H NMR spectra of compounds 15a and b indicated the absence of the phenolic
and oxime OH groups. In this sense, the phosphacumulene ylides 3 and 6 act as Lewis bases
that facilitate the dehydration process. Moreover, when the oximes 14a,b were refluxed in
THF for 5 h, compounds 15a,b were obtained only after addition of the base triethylamine
to the reaction mixture (Scheme 3).
The reaction of 7-hydroxy-5-methyoxy-2-methyl-4-oxo-4H-chromene-6-carbald
ehyde (16) with the phosphacumulenes 3 and 6 was also investigated. Compound
16 was prepared by oxidation of the chromenone 1a with K2Cr2O7 and H2SO4.17
Treatment of the chromene carbaldehyde 16 with the phosphoranes 3 or 6 in THF for
10 h in case of 3 and for 15 h in the case of 6 leads to the formation of 5-methoxy-2-
methyl-8-phenylimino-8H-pyrano[3,2-g]chromen-4-one (18a) and 5-methoxy-8-methyl-
pyrano[3,2-g]chromen-2,6-dione (18b), respectively. Compounds 18a,b are formed
through intramolecular cyclization of the intermediates 17. The chromenone 18a shows in
the mass spectrum m/z at 335 [M+2H]. In the 1H NMR spectrum, no signals corresponding
1
to OH and CHO protons are observed, which appear, however, in the H NMR spectrum
of 16 (Scheme 4).
The reaction of 7-hydroxy-5-methoxy-2-methyl-6-[(phenylimino)methyl]-4H-chro
men-4-one (19) with the phosphacumulene 3 proceeds in THF at room temperature to give
the chromenone 18a together with N-phenyliminotriphenylphosphorane (21). However
when chromenone 19 was allowed to react with phosphacumulene 6 in THF at room
temperature for 12 h, the ester (20b) was exclusively obtained. When compound 20b was
heated in toluene, cyclization occurs with formation of the corresponding 5-methoxy-8-
methyl-pyrano[3,2-g]chromene-2,6-dione (18b) and the phosphinimine 21. It is evident
that formation of compounds 18a,b involves the intermediates 20a,b, which spontaneously
lactonize only in case of 20a. In the mass spectrum of 20b, the molecular ion peak was
found at m/z = 611 (M+, 87%). The 31P NMR spectrum of 20b displays a signal at δ =
22.5 ppm (Scheme 4).

194
S. S. MAIGALI ET AL.
H
C
H
C
C6
H
C
5
H
OC
3
C
O
C
O
C
P
(
H
5
H
)
3
H
C
6
H
H
OC
3
C
C
X
H
P
)
3
C
(
H
C6
C
6
5
5
C
O
=
=
-
O
X
3 X
6 X
,
N
H
C6
,
5
O
R
O
H
O
a-
12
d
R
a
=
H
11
R
,
=
b R
,
H
OC
3
H
H
O
C
H
C6
C
C
5
H
OC
3
H
OC
3
H
C
3
enza e
ld h d
y
e
b
P =
)
+
H
C
(
O
6
5 3
X
O
a
N OH
O
O
H
O
R
R
a
=
=
-
=
13
R
H X
N
X
O
X
H
C6
5
,
,
;
a
=
H
2
R
,
,
=
=
=
-
N
b R
H
OC
H
C6
5
;
3
=
b R
H
3
OC
c
,
=
R
H X
;
OC
=
d R
H
;
3
O
,
NH OH HCl
,
2
H
C
3
H
OC
3
C
H
C
H
OC
3
3
NOH
C
P
C
X
H
C
(
)
5
3
6
N
H
O
O
=
=
-
3 X
6 X
,
N
H
C6
5
,
O
O
R
O
R
a
=
=
14
R
H
,
a
=
15
R
H
,
b R
H
3
OC
,
=
b R
H
3
OC
,
Scheme 3
We now report a study on the reaction of the phosphacumulenes 3 and 6 with 4-
methoxy-5-oxo-5H-furo[3,2-g]chromene-6-carbaldehyde (22a) and 4,9-dimethoxy-5-oxo-
5H-furo[3,2-g]chromene-6-carbaldehyde (22b). Compounds 2a,b are used for the synthesis
of the carbaldehydes 22a,b directly via Vielsmeier–Haack reaction.18,19 When the reaction
of the chromene carbaldehyde 22a with the phosphorane 3 was performed in boiling toluene,
the corresponding chromen-5-one (25a) was obtained. Furthermore reaction of compound
22b with 3 under the same experimental conditions afforded chromen-5-one (25b) and
chromen-2-one (26). This reaction proceeds via a [2+2]-cycloaddition of the carbonyl group
in 22a,b to the ylidic C–P bond of the phosphorane 3 to give the oxaphosphetane 23.20–22
Elimenation of TPPO from 23 leads to the formation of the unstable ketene 24, which
dimerizes to give 25a,b. However in case of the reaction of the chromene carbaldehyde
22b with the phosphorane 3, the dimer 25b was isolated together with the cyclobutylidene
chromenone 26, which is formed by the addition of 3 to the ketene 24 (Scheme 5). The mass
spectrum of compound 25a shows a peak at m/z = 343 (M+, 80%), which corresponds to
the molecular ion peak of the monomer. This behavior is frequently observed in the mass

CHROMENONE PHOSPHANYLIDENE AND CYCLOBUTYLIDENE DERIVATIVES
195
O
O
OCH3
O
O
OCH3
(C6H5)3P
C C X
HC
K2Cr2O7
H2SO4
3, X = N- C6H5
6, X = O
CH3
O
CH3
HO
O
1a
16
H
O
O
OCH3
C
O
CH
O
O
(C6H5)3P
OCH3
H
NaOH
C
C6H5
N
C
X
CH3
O
aniline hydrochloride
CH3
HO
17
19
(C6H5)3P
-
(C6H5)3P=O
C
C
X
3, X = N- C6H5
6, X = O
O
OCH3
H
O
OCH3
C
C6H5
N
-
(C6H5)3P
N
C6H5
CH
(C6H5)3P
X
CH3
C
X
O
O
21
CH3
O
O
18a, X = N- C6H5
b, X = O
20a, X = N- C6H5
b, X = O
Scheme 4
O
3 C
(C6H5)3
P
C C N C6H5
O
OCH
O
O
OCH3
CH3
CH
O
O
O
OCH3
POCl3
DMF
(C6H5)3P C C N C6H5
CH
O
OH
3
O
R
R
22a, R= H
b, R = OCH3
O
2a, R= H
R
b, R = OCH3
23
- P(C6H5)3=O
OCH3
O
O
N
C6H5
O
C
H
OCH3
OCH3
O
C
C
N C6H5
HC
C
O
C6H5
N
H
R
O
O
O
O
25a, R = H
b, R = OCH3
R
R
24
+
N C6H5
P(C6H5)3
C6H5
O
O
H
OCH3
OCH3
C
N
O
26
Scheme 5

196
S. S. MAIGALI ET AL.
spectra of a variety of dimeric products.23 The 31P NMR spectrum of compound 26 shows
a signal at δ = 20.7 ppm, which fits well to a four-membered phosphorane ring structure.24
The reactions of the carbaldehydes 22a,b with the phosphacumulene 6 were per-
formed in boiling toluene and yield compounds (27a,b), respectively. No dimerization
product was observed (Scheme 6). The 31P NMR signals of compounds 27a and 27b are
found at 21.72 and 21.66 ppm, respectively.
O
O
O
OCH3
CH
P(C6H5)3
(C6H5)3P
C C O
22a,b
O
O
6
R
27a, R = H
b, R = OCH3
Scheme 6
CONCLUSION
The fruitful organic chemistry of the phosphacumulene ylides 3 and 6 originates from
the unique combination of ylidic and ketene properties resulting in a dipolar electronic
structure. The first attack is always that of an electrophile to the ylidic carbanionic carbon
atom. The intermediate thus formed can further react in different ways. The outcome and
progress of these reactions, which also comprise a selective intramolecular Wittig olefination
as the actual ring closure step, lead to the formation of a great variety of carbocyclic and
heterocyclic organic compounds. Moreover, the difference in the nucleophilic character
and reactivity of the phosphacumulene ylides (3 < 6) becomes evident in this study.25
Reagent 3 reacts more smoothly than reagent 6. These results show new applications of
phosphacumulene ylides in the synthesis of some pharmaceutically interesting naturally
occurring furo- and pyrano-chromenones.
EXPERIMENTAL
Melting points (mp) were measured with a Gallenkamp electrothermal digital melting
points apparatus. IR spectra were measured as KBr pellets with a PerkinElmer Infrared
1
spectrophotometer Model 157. H, 13C, and 31P NMR spectra were recorded in CDCl3
or d6-DMSO with a Varian Spectrometer at 500.1, 125.8, and 202.4 MHz, respectively,
using tetramethylsilane (TMS) as internal and 85% H3PO4 as external reference. The
mass spectra were recorded at 70 eV with a Kratos MS equipment or a Varian MAT311A
Spectrometer. Elemental analyses were performed using the Elementar vario El-Germany
Instrument. The experimental values agreed well with the calculated ones.
Reaction of 1-(6-Hydroxy-4-methoxybenzofuran-5-yl)ethanone (2a)
with (N-phenyliminovinylidene)triphenylphosphorane (3)
A mixture of (N-phenyliminovinylidene)triphenylphosphorane (3) (0.37 g, 0.01 mol)
and 1-(6-hydroxy-4-methoxybenzofuran-5-yl) ethanone (2a) (0.20 g, 0.01 mol) in THF (40

CHROMENONE PHOSPHANYLIDENE AND CYCLOBUTYLIDENE DERIVATIVES
197
mL) was magnetically stirred at room temperature for 8 h. During which the color of the
mixture changed from yellow to brown. The solvent was removed under reduced pressure
and the residue was chromatographed on silica gel using petroleum ether (60–80 ◦C): ethyl
acetate (70: 30) as eluent to give compound 5a as yellow crystals; yield 65%; mp 135 ◦C.
1H NMR (500.1 MHz, CDCl3): δ = 2.55 (d, JHH = 2.5 Hz, 3H, CH3), 4.09 (s, 3H, OCH3),
6.09 (q, JHH = 2.5 Hz, 1H, 6-H), 6.98 (d, JHH = 2.30 Hz, 1H, 3-H of furan ring), 7.01–7.35
(m, 5H, arom-H), 7.14 (s, 1H, 9-H), 7.57 (d, JHH = 2.30 Hz, 1H, 2-H of furan ring). 13
C
NMR (125.8 MHz, CDCl3): δ = 24.3 (CH3), 61.0 (OCH3), 90.7 (C-9), 106.0 (C-3), 110.2
(C-6), 145.6 (C-5), 146.3 (C-2), 152.2 (C-4), 158.3 (C = N). MS: m/z (%) = 305 (M+,
35.5), 202 (M+ − (–C = N–C6H5), 28.5). Anal. Calcd. for C19H15O3N (305.33): C, 74.74;
H, 4.95; N, 4.59. Found: C, 74.52; H, 4.59; N, 4.25%.
When the reaction was repeated using 2a (0.20 g, 0.01 mol) and 3 (0.75 g, 0.02 mol),
the same product 5a was isolated.
Reaction of 1-(6-Hydroxy-4,7-dimethoxybenzofuran-5-yl)ethanone (2b)
with (N-phenyliminovinylidene)triphenylphosphorane (3)
A solution of (N-phenyliminovinylidene)triphenylphosphorane (3) (0.37 g, 0.01 mol)
in THF (20 mL) was added dropwise with stirring to a solution of 1-(6-Hydroxy-4,7-
dimethoxy-benzofuran-5-yl)ethanone (2b) (0.25 g, 0.01 mol) in THF (20 mL). The re-
action mixture was kept at room temperature for 10 h. The progress of the reaction was
followed by thin layer chromatography (TLC). THF was removed under reduced pres-
sure, and the r◦esidue was subjected to silica gel column chromatography using petroleum
ether (60–80 C): ethyl acetate (80: 20) as eluent to give the two compounds 5b and
8b.
◦
1
Compound 5b: Yellow crystals; yield 65%; mp 128 C (sharp). H NMR (500.1
MHz, CDCl3): δ = 2.56 (d, JHH = 2.50 Hz, 3H, CH3), 3.81 (s, 3H, OCH3), 4.01 (s, 3H,
OCH3), 6.28 (q, JHH = 2.50 Hz, 1H, 6-H), 6.89 (d, JHH = 2.30 Hz, 1H, 3-H of furan ring),
6.95–7.35 (m, 5H, arom-H), 7.57 (d, JHH = 2.30 Hz, 1H, 2-H of furan ring). 13C NMR
(125.8 MHz, CDCl3): δ = 23.6 (CH3), 60.3 (OCH3), 61.7 (OCH3), 105.0 (C-3), 110.2
(C-6), 135.2 (C-9), 143.8 (C-5), 145.7 (C-2), 150.1 (C-4), 156.0 (C N). MS: m/z (%) =
335 (M+, 27.60), 232 (M+ − (–C N–C6H5), 5.20). Anal. Calcd. for C20H17O4N (335.35):
C, 71.63; H, 5.11; N, 4.18. Found: C, 71.67; H, 5.12; N, 4.34%.
◦
Compound 8b: Yellow crystals; yield 25%; mp 216 C. IR (ν, cm−1): 1610 and
1591 (C C), 1705 (lactone carbonyl group). 1H NMR (500.1 MHz, CDCl3): δ = 2.64 (d,
JHH = 2.5 Hz, 3H, CH3), 4.07 (s, 3H, OCH3), 4.17 (s, 3H, OCH3), 6.13 (q, JHH = 2.5 Hz,
1H, 6-H), 6.96 (d, JHH = 2.3 Hz, 1H, 3-H of furan ring), 7.63 (d, JHH = 2.3 Hz, 1H, 2-H of
furan ring). 13C NMR (125.8 MHz, CDCl3): δ = 24.0 (CH3), 61.5 (OCH3), 61.7 (OCH3),
105.0 (C-3), 113.9 (C-6), 133.5 (C-9), 146.0 (C-2), 149.0 (C-4), 151.2 (C-5), 160.2 (C O,
lactone). MS: m/z (%) = 260 (M+, 40.0), 232 (M+ − (C O), 25.0). Anal. Calcd. for
C14H12O5 (260.24): C, 64.61; H, 4.65. Found: C, 64.37; H, 4.39%.
Compound 5b was boiled in toluene for 3 h; the toluene was removed under reduced
pressure and the residue was subjected to silica gel column chromatography using petroleum
◦
ether (60–80 C): chloroform (70: 30) as an eluent to give compound 8b and traces of
compound 5b.

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S. S. MAIGALI ET AL.
Reaction of 1-(6-Hydroxy-4-methoxybenzofuran-5-yl)ethanone (2a)
or 1-(6-Hydroxy-4,7-di-methoxybenzofuran-5-yl)ethanone (2b)
with (2-Oxovinylidene)triphenylphosphorane (6)
To a solution of 1-(6-hydroxy-4-methoxybenzofuran-5-yl) ethanone (2a) (0.20 g, 0.01
mol) or 1-(6-hydroxy-4,7-dimethoxybenzofuran-5-yl) ethanone (2b) (0.25 g, 0.01 mol) in
dry THF (20 mL) was added a solution of (2-oxovinylidene)triphenylphosphorane (6) (0.30
g, 0.01 mol) in dry THF (20 mL). The reaction mixture was stirred at room temperature
during 8–12 h. THF was removed under reduced pressure. The r◦esidue was subjected to
silica gel column chromatography using petroleum ether (60–80 C): acetone (70: 30) as
eluent to give 7a or 7b, respectively.
Compound 7a: Pale yellow crystals; yield 70%; mp 260 ◦C. 1H NMR (500.1 MHz,
CDCl3): δ = 2.56 (s, 3H, CH3), 4.06 (s, 3H, OCH3), 5.23 (d, 2JPH = 15.0 Hz, 1H, H–C P),
6.86 (d, JHH = 2.3 Hz, 1H, 3-H of furan ring), 7.26 (s, 1H, 7-H), 7.58 (d, JHH = 2.3 Hz,
1H, 2-H of furan ring), 7.50–7.74 (m, 15H, arom-H). 13C NMR (125.8 MHz, CDCl3): δ =
32.6 (CH3), 60.8 (OCH3), 95.9 (C-7), 105.3 (C-3), 116.3 (C-5), 145.8 (C-2), 151.4 (C-4),
153.7 (C-6), 155.4 (–C P), 161.0 (–O–C O), 202.0 (CH3–C O). 31P NMR (202.4 MHz,
CDCl3): δ = 17.4. MS: m/z (%) = 508 (M+, 25.3), 262 (P(C6H5)3, 100), 246 (M+
−
P(C6H5)3, 5.90). Anal. Calcd. for C31H25O5P (508.5): C, 73.22; H, 4.96; P, 6.09. Found:
C, 73.12; H, 4.51; P, 6.43%.
◦
1
Compound 7b: Brown crystals; yield 35%; mp 200 C. H NMR (500.1 MHz,
CDCl3): δ = 2.22 (s, 3H, CH3), 3.90 (s, 3H, OCH3), 4.10 (s, 3H, OCH3), 5.26 (d, 2JPH
=
15.0 Hz, 1H, H–C P), 6.80 (d, JHH = 2.3 Hz, 1H, 3-H of furan ring), 7.59 (d, JHH = 2.3
Hz, 1H, 2-H of furan ring), 7.26–7.74 (m, 15H, arom-H). 13C NMR (125.8 MHz, CDCl3):
δ = 32.8 (CH3), 60.8 (OCH3), 61.3 (OCH3), 106.3 (C-3), 113.0 (C-5), 135.5 (C-7), 145.9
(C-2), 150.2 (C-4), 153.0 (C-6), 154.4 (–C P), 161.2 (–O–C O), 201.0 (CH3–C O). 31
P
NMR (202.4 MHz, CDCl3): δ = 17.8. MS: m/z (%) = 540 (M+2, 22.6), 262 (P(C6H5)3,
90.0), 278 (M+2 − P(C6H5)3, 24.3). Anal. Calcd. for C32H27O6P (538.53): C, 71.37; H,
5.05; P, 5.75. Found: C, 71.21; H, 4.99; P, 5.52%.
When compounds 7a and 7b were boiled in toluene, they were converted into com-
pounds 8a and 8b, respectively, and TPPO.
Compound 8a: Yellow crystals; yield 55%; mp 172 ◦C, IR (ν, cm−1): 1618 and 1591
(C C), 1731 (lactone carbonyl group). 1H NMR (500.1 MHz, CDCl3): δ = 2.61 (d, JHH
=
2.5 Hz, 3H, CH3), 4.14 (s, 3H, OCH3), 6.06 (q, JHH = 2.5 Hz, 1H, 6-H), 6.95 (s, 1H, 9-H),
6.98 (d, JHH = 2.3 Hz, 1H, 3-H of furan ring), 7.56 (d, JHH = 2.3 Hz, 1H, 2-H of furan
ring). 13C NMR (125.8 MHz, CDCl3): δ = 24.4 (CH3), 60.8 (OCH3), 95.1 (C-9), 105.2
(C-3), 113.5 (C-6), 144.9 (C-2), 151.9 (C-4), 152.9 (C-5), 160.9 (C O). MS: m/z (%) =
230 (M+, 100), 202 (M+ − (C O), 28.0). Anal. Calcd. for C13H10O4 (230.22): C, 67.82;
H, 4.38. Found: C, 67.51; H, 4.21%.
Reaction of Phosphoranes 3 and 6 with Compounds 11a,b:
General Procedure
A solution of 11a or 11b (0.01 mol) in toluene (20 mL) was added under reflux
and stirring to a solution of phosphacumulenes 3 or 6 (0.02 mol) in toluene (20 mL). The
reaction mixture was left for 5 h when 3 was used and for 8 h in the case of 6. The progress
of the reaction was monitored by TLC. Toluene was distilled off under reduced pressure,

CHROMENONE PHOSPHANYLIDENE AND CYCLOBUTYLIDENE DERIVATIVES
199
and the remaining material was chromatographed on silica gel to give TPPO (mp and mixed
mp 151 ◦C) and compounds 13a–d.
N-(4-Methoxy-5-styryl-7H-furo[3,2-g]chromen-7-ylidene)benzenamine
(13a)
Orange crystals; mp 168 ◦C; yield 87%; chromatography on silica gel with petroleum
ether/chloroform as eluent (60: 40). 1H NMR (500.1 MHz, CDCl3): δ = 4.03 (s, 3H, OCH3),
6.32 (s, 1H, 6-H), 6.88 (d, JHH = 2.3 Hz, 1H, 3-H of furan ring), 6.89 (s, 1H, 9-H), 7.53
(d, JHH = 2.3 Hz, 1H, 2-H of furan ring), 6.74 (d, JHH = 16.1 Hz, 1H, CH CH), 7.75
(d, JHH = 16.1 Hz, 1H, CH CH), 7.08–7.48 (m, 10H, arom-H). 13C NMR (125.8 MHz,
CDCl3): δ = 61.6 (OCH3), 95.6 (C-9), 106.6 (C-3), 108.7 (C-6), 132.0 (CH CH), 127.0
(CH CH), 146.3 (C-2), 150.2 (C-4), 152.1 (C-5), 156.0 (C N). MS: m/z (%) = 393 (M+,
32.9), 290 (M+ − (–CH CH–C6H5), 100), 199 (M+ − (–CH CH–C6H5) and (–N–C6H5),
2.56). Anal. Calcd. for C26H19O3N (393.43): C, 79.37; H, 4.87; N, 3.56. Found: C, 79.20;
H, 4.68; N, 3.45%.
N-(4,9-Dimethoxy-5-styryl-7H-furo[3,2-g]chromen-7-ylidene)-
benzenamine (13b)
◦
Yellow crystals; yield 68%; mp 153–155 C; chromatography on silica gel with
1
petroleum ether/acetone as eluent (60: 40) and recrystallized from benzene. H NMR
(500.1 MHz, CDCl3): δ = 3.86 (s, 3H, OCH3), 4.02 (s, 3H, OCH3), 6.32 (s, 1H, 6-H), 6.87
(d, JHH = 2.3 Hz, 1H, 3-H of furan ring), 6.76 (d, JHH = 16.1 Hz, 1H, CH CH), 7.83 (d,
JHH = 16.1 Hz, 1H, CH CH), 7.00–7.57 (m, 10H, arom-H), 7.76 (d, JHH = 2.3 Hz, 1H, 2-H
of furan ring). 13C NMR (125.8 MHz, CDCl3): δ = 61.6 (OCH3), 62.1 (OCH3), 106.9 (C-3),
109.7 (C-6), 132.2 (CH CH), 127.0 (CH CH), 137.0 (C-9), 146.2 (C-2), 149.7 (C-4),
152.4 (C-5), 155.0 (C N). MS: m/z (%) = 424 (M+, 35.6), 321 (M+ − (–CH CH–C6H5),
88.0), 230 (M+ − (–CH CH–C6H5) and (–N–C6H5), 14.6). Anal. Calcd. for C27H21O4N
(423.46): C, 76.58; H, 5.00; N, 3.31. Found: C, 76.21; H, 4.87; N, 3.27%.
4-Methoxy-5-styryl-7H-furo[3,2-g]chromen-7-one (13c)
◦
Yellow crystals; yield 75%; mp 175 C (sharp); chromatography on silica gel with
n-hexane/ethyl acetate (70: 30) as eluent. IR (ν, cm−1): 1710 (lactone carbonyl group),
1625 (C C). 1H NMR (500.1 MHz, CDCl3): δ = 4.02 (s, 3H, OCH3), 6.39 (s, 1H, 6-H),
6.88 (d, JHH = 2.3 Hz, 1H, 3-H of furan ring), 6.94 (s, 1H, 9-H), 7.61 (d, JHH = 2.3 Hz,
1H, 2-H of furan ring), 7.03 (d, JHH = 16.1 Hz, 1H, CH CH), 7.87 (d, JHH = 16.1 Hz,
1H, CH CH), 6.98–7.32 (m, 5H, arom-H). 13C NMR (125.8 MHz, CDCl3): δ = 62.0
(OCH3), 97.2 (C-9), 104.9 (C-3), 111.2 (C-6), 131.1 (CH CH), 125.9 (CH CH), 145.7
(C-2), 148.0 (C-4), 150.8 (C-5), 160.3 (C O). MS: m/z (%) = 318 (M+, 100), 215 (M+ −
(–CH CH–C6H5), 19.2), 187 (M+ − (–CH CH–C6H5) and (C O), 11.4). Anal. Calcd.
for C20H14O4 (318.32): C, 75.46; H, 4.43. Found: C, 75.09; H, 4.03%.
4,9-Dimethoxy-5-styryl-7H-furo[3,2-g]chromen-7-one (13d)
◦
Orange crystals; yield 65%; mp 186–187 C; chromatography on silica gel with
petroleum ether/acetone (80: 20) as eluent. IR (ν, cm−1): 1709 (lactone carbonyl group),
1621 (C C). 1H NMR (500.1 MHz, CDCl3): δ = 3.91 (s, 3H, OCH3), 4.18 (s, 3H, OCH3),

200
S. S. MAIGALI ET AL.
6.41 (s, 1H, 6-H), 6.93 (d, JHH = 2.3 Hz, 1H, 3-H of furan ring), 7.57 (d, JHH = 2.3 Hz,
1H, 2-H of furan ring), 7.03 (d, JHH = 16.1 Hz, 1H, CH CH), 7.88 (d, JHH = 16.1 Hz, 1H,
CH CH), 7.00–7.23 (m, 5H, arom-H). 13C NMR (125.8 MHz, CDCl3): δ = 61.6 (OCH3),
62.1 (OCH3), 104.7 (C-3), 110.2 (C-6), 132.9 (CH CH), 126.8 (CH CH), 136.8 (C-9),
145.4 (C-2), 149.3 (C-4), 155.6 (C-5), 160.4 (C O). MS; m/z (%) = 348 (M+, 68.8), 245
(M+ − (–CH CH–C6H5), 18.0), 217 (M+ − (–CH CH–C6H5) and (C O), 12.2). Anal.
Calcd. for C21H16O5 (348.35): C, 72.41; H, 4.63. Found: C, 72.67; H, 4.34%.
Reaction of Oxime 14a with Phosphacumulenes 3 and 6
Phosphacumulene 3 (0.37 g, 0.01 mol) or 6 (0.30 g, 0.01 mol) was added to oxime
14a (0.22 g, 0.01 mol) in THF (30 mL) under stirring at room temperature for 5 h. THF was
distilled off under reduced pressure, and the remaining residue was chromatographed on
silica gel using petroleum ether (60–80 ◦C)/et◦hyl acetate as eluent (80: 20) to give isoxazole
1
15a as white crystals, yield 80%, mp 115 C (sharp). H NMR (500.1 MHz, CDCl3):
δ = 2.66 (s, 3H, CH3), 4.09 (s, 3H, OCH3), 7.27 (s, 1H, 8-H), 6.99 (d, JHH = 2.3 Hz, 1H,
3-H of furan ring), 7.57 (d, JHH = 2.3 Hz, 1H, 2-H of furan ring). 13C NMR (125.8 MHz,
CDCl3): δ = 18.2 (CH3), 61.1 (OCH3), 93.5 (C-8), 105.9 (C-3), 147.0 (C-2), 149.3 (C-4),
155.1 (C-5). MS: m/z (%) = 203 (M+, 100), 189 (M+ − (CH2), 46.1). Anal. Calcd. for
C11H9NO3 (203.19): C, 65.02; H, 4.46; N, 6.89. Found: C, 64.92; H, 4.35; N, 6.52%.
Reaction of Oxime 14b with Phosphacumulenes 3 and 6
A solution of phosphacumulene 3 (0.37 g, 0.01 mol) or 6 (0.3 g, 0.01 mol) in THF
(20 mL) was added to a solution of oxime 14b (0.26 g, 0.01 mol) in THF (20 mL) with
stirring at room temperature for 5 h. THF was distilled off under reduced pressure, and
the remaining residue was chromatographed on silica gel using petroleum ether (60–80
◦C)/ethyl acetate (60: 40) as eluent to give isoxazole 15b as white crystals, yield 80%, mp
152–154 ◦C. 1H NMR (500.1 MHz, CDCl3), δ = 2.65 (s, 3H, CH3), 4.05 (s, 3H, OCH3),
4.17 (s, 3H, OCH3), 6.99 (d, JHH = 2.3 Hz, 1H, 3-H of furan ring), 7.57 (d, JHH = 2.3 Hz,
1H, 2-H of furan ring). 13C NMR (125.8 MHz, CDCl3): δ = 18.0 (CH3), 60.9 (OCH3), 61.3
(OCH3), 105.0 (C-3), 135.7 (C-8), 146.4 (C-2), 151.1 (C-4), 156.6 (C-5). MS: m/z (%) =
233 (M+, 100), 219 (M+ − (CH2), 49.0). Anal. Calcd. for C12H11NO4 (233.22): C, 61.80;
H, 4.75; N, 6.01. Found: C, 61.48; H, 4.86; N, 6.09%.
When a solution of the oximes 14a,b in THF was refluxed for 5 h with a few drops
of triethylamine, compounds 15a,b were obtained.
Reaction of 4H-chromene-6-carbaldehyde 16 with Phosphacumulenes
3 or 6
A mixture of 16 (0.26 g, 0.01 mol) and phosphacumulenes 3 or 6 (0.01 mol) in dry
THF (20 mL) was stirred at room temperature for 10 h in case of 3 and for 15 h in case of
6, until no more of the starting materials could be detected (TLC). THF was distilled off
under reduced pressure and the remaining residue was chromatographed on silica gel using
n-hexane/acetone (80: 20) as eluent to give 18a or 18b, respectively, and TPPO (mp and
mixed mp 151 ◦C).

CHROMENONE PHOSPHANYLIDENE AND CYCLOBUTYLIDENE DERIVATIVES
201
5-Methoxy-2-methyl-8-phenylimino-8H-pyrano[3,2-g]chromen-4-one
(18a)
◦
Yellow crystals; yield 70%; mp 140 C. IR (ν, cm−1): 1663 (γ -pyrone carbonyl
group), 1625 (C N). 1H NMR (500.1 MHz, CDCl3): δ = 2.35 (d, JHH = 2.5 Hz, 3H, CH3),
4.02 (s, 3H, OCH3), 6.08 (q, JHH = 2.5 Hz, 1H, 7-H), 6.40 (d, JHH = 9.7 Hz, 1H, H of
α-pyrone ring), 8.08 (d, JHH = 9.7 Hz, 1H, H of α-pyrone ring), 7.08–7.65 (m, 6H, arom-H,
10-H). 13C NMR (125.8 MHz, CDCl3): δ = 20.1 (CH3), 64.3 (OCH3), 101.4 (C-10), 111.7
(C-7), 115.7 (C-3), 138.4 (C-4), 156.8 (C-5), 159.5 (C N), 165.1 (C-8), 176.5 (γ -pyrone
carbonyl group). MS: m/z (%) = 335 (M+2, 32.8), 258 (M+2 − (–C6H5), 19.4), 230 (M+2
− (C N–C6H5), 26.9). Anal. Calcd. for C20H15O4N (333.34): C, 72.06; H, 4.54; N, 4.20.
Found: C, 72.35; H, 4.29; N, 4.06%.
5-Methoxy-8-methyl-pyrano[3,2-g]chromene-2,6-dione (18b)
Brown powder; yield 45%, mp 235 ◦C (sharp). IR (ν, cm−1): 1663 (γ -pyrone carbonyl
1
group) and 1746 (lactone carbonyl group). H NMR (500.1 MHz, CDCl3): δ = 2.36 (d,
JHH = 2.5 Hz, 3H, CH3), 4.03 (s, 3H, OCH3), 6.09 (q, JHH = 2.5 Hz, 1H, 7-H), 7.09 (s,
1H, 10-H), 6.40 (d, JHH = 9.7 Hz, 1H, H of α-pyrone ring), 8.09 (d, JHH = 9.7 Hz, 1H, H
of α-pyrone ring). 13C NMR (125.8 MHz, CDCl3): δ = 20.1 (CH3), 64.2 (OCH3), 101.3
(C-10), 111.7 (C-7), 115.7 (C-3), 138.4 (C-4), 156.4 (C-5), 160.0 (lactone carbonyl group),
164.8 (C-8), 176.4 (γ -pyrone carbonyl group). MS: m/z (%) = 258 (M+, 34.4), 230 (M+
− (C O), 13.0). Anal. Calcd. for C14H10O5 (258.23): C, 65.12; H, 3.90. Found: C, 65.07;
H, 3.79%.
Reaction of 4H-Chromen-4-one 19 with Phosphacumulene 3
A mixture of 19 (0.30 g, 0.01 mol) and phosphacumulene 3 (0.75 g, 0.02 mol) was
stirred in 30 mL of dry THF at room temperature for 8 h. THF was distilled under reduced
pressure, and the residue was crystallized from benzene to give compound 18a and the
phosphinimine 21.
Reaction of 4H-Chromen-4-one 19 with Phosphacumulene 6
A mixture of 19 (0.30 g, 0.01 mol) and phosphacumulene 6 (0.6 g, 0.02 mol) was
stirred in 30 mL of dry THF at room temperature for 12 h. THF was distilled off under
reduced pressure, and the remaining residue was crystallized from cyclohexane to give
compound 20b.
◦
1
Compound 20b: Yellow crystals; yield 75%; mp 110 C. H NMR (500.1 MHz,
CDCl3): δ = 2.24 (d, JHH = 2.5, 3H, CH3), 3.83 (s, 3H, OCH3), 4.57 (2JPH = 15.4 Hz,
1H, –P C–H), 6.14 (q, JHH = 2.5, 1H, vinyl-H), 7.09 (s, 1H, 8-H), 7.01–7.98 (m, 20H,
arom-H), 8.39 (s, 1H, –N C–H). 13C NMR (125.8 MHz, CDCl3): δ = 20.7 (CH3), 61.8
(OCH3), 111.0 (C-3), 150.6 (C-2), 153.5 (C-5), 155.3 (P C), 157.5 (C-7), 159.8 (N C),
164.0 (O = C–O), 175.7 (pyrone carbonyl ring). 31P NMR (202.4 MHz, CDCl3): δ = 22.5.
MS: m/z (%) = 611 (M+, 87.0), 262 (P(C6H5)3, 66.1), 349 (M+ − P(C6H5)3, 24.0). Anal.
Calcd. for C38H30O5NP (611.62): C, 74.62; H, 4.94; N, 2.29; P, 5.06. Found: C, 74.22; H,
4.72; N, 2.10; P, 5.00%.

202
S. S. MAIGALI ET AL.
When the compound 20b was boiled in toluene, it was converted to compound 18b
and the phosphinimine 21.
Reaction of Carbaldehyde 22a with Phosphorane 3
A solution of phosphacumulene 3 (0.75 g, 0.02 mol) in 20 mL of toluene was added
dropwise with stirring and refluxing to a solution of 22a (0.24 g, 0.01 mol) in 20 mL
of toluene. The reaction mixture was stirred for 5 h. The progress of the reaction was
monitored by TLC. Toluene was distilled off under reduced pressure, and the remaining
residue was crystallized from cyclohexane to give compound 25a as yellow crystals, yield
78%, mp 192 ◦C (sharp). IR (ν, cm−1): 1663 (γ -pyrone carbonyl group) and 1610 (C C).
1H NMR (500.1 MHz, CDCl3): δ = 4.03 (s, 6H, OCH3), 6.47 (s, 2H, –CH C), 6.82 (s,
2H, 9-H), 6.70 (d, JHH = 2.3 Hz, 2H, 3-H of furan rings), 7.53 (d, JHH = 2.3 Hz, 2H, 2-H
of furan rings), 7.25–7.68 (m, 12H, arom-H, 7-H). 13C NMR (125.8 MHz, CDCl3): δ =
62.0 (OCH3), 159.0 (C N), 177.3 (pyrone carbonyl ring). MS: m/z (%) = 343 (M+ for
monomer, 80.0). Anal. Calcd. for C42H26O8N2 (686.66): C, 73.46; H, 3.82; N, 4.08. Found:
C, 73.25; H, 3.50; N, 4.00%.
Reaction of Carbaldehyde 22b with Phosphorane 3
A mixture of phosphacumulene 3 (0.75 g, 0.02 mol) and 22b (0.27 g, 0.01 mol) in
toluene (30 mL) was refluxed for 8 h. During this time the color of the reaction solution
changed from yellow to dark brown. Toluene was distilled off under reduced pressure and
the remaining residue was chromatographed on silica gel using petroleum ether (60–80
◦C)/ethyl acetate (50: 50) as eluent to give the products 25b and 26.
◦
Compound 25b: Yellow crystals; yield 30%; mp 215 C. IR (ν, cm−1): 1672 (γ -
1
pyrone carbonyl group) and 1638 (C C). H NMR (500.1 MHz, CDCl3): δ = 3.65 (s,
6H, OCH3), 3.87 (s, 6H, OCH3), 6.66 (s, 2H, –CH C), 6.69 (d, JHH = 2.3 Hz, 2H, 3-
H of furan rings), 7.57 (d, JHH = 2.3 Hz, 2H, 2-H of furan rings), 6.86–7.49 (m, 12H,
arom-H, 7-H). 13C NMR (125.8 MHz, CDCl3): δ = 61.2 (OCH3), 62.0 (OCH3), 105.0 (C-
3), 119.7 (C CH), 124.6 (C-9), 144.8 (CH C), 145.2 (C-2), 145.7 (C-4), 157.9 (C N),
177.5 (pyrone carbonyl ring). MS: m/z (%) = 373 (M+ for monomer, 45). Anal. Calcd. for
C44H30O10N2 (746.72): C, 70.77; H, 4.05; N, 3.75. Found: C, ◦70.75; H, 4.09; N, 3.53%.
1
Compound 26: Yellow crystals; yield 55%; mp 172 C. H NMR (500.1 MHz,
CDCl3): δ = 3.88 (s, 3H, OCH3), 4.02 (s, 3H, OCH3), 6.66 (d, JHH = 2.3 Hz, 1H, 3-H
of furan ring), 7.23 (s, 1H, HC-7), 7.44 (s, 1H, CH C), 7.45 (d, JHH = 2.3 Hz, 1H, 2-H
of furan ring), 7.50–7.98 (m, 25H, arom-H). 13C NMR (125.8 MHz, CDCl3): δ = 61.0
(OCH3), 61.5 (OCH3), 105.0 (C-3), 143.0 (C-4), 145.0 (C-2), 150.8 (C-7), 153.8 (d, 1JPC
= 93.0 Hz, C P), 180.8 (HC C), 151.9 (HC C), 165.2 (C N), 177.2 (pyrone carbonyl
ring). 31P NMR (202.4 MHz, CDCl3): δ = 20.7. Anal. Calcd. for C48H35O5N2P (750.78):
C, 76.79; H, 4.70; N, 3.73; P, 4.13. Found: C, 76.61; H, 4.63; N, 3.69; P, 4.22%.
Reaction of (2-Oxovinylidene)triphenylphosphorane (6) with
Compounds 22a,b
To a solution of (2-oxovinylidene)triphenylphosphorane (6) (0.6 g, 0.02 mol) in 20
mL of toluene was added a solution of 22a or 22b (0.01 mol) in 20 mL of toluene. The
reaction mixture was refluxed for 12 h. The solvent was removed under reduced pressure,

CHROMENONE PHOSPHANYLIDENE AND CYCLOBUTYLIDENE DERIVATIVES
203
and the residue was chromatographed on silica gel using n-hexane/acetone (70: 30) as
eluent to give 27a or 27b, respectively.
◦
Compound 27a: Yellow crystals; yield 67%; mp 143–145 C. IR (ν, cm−1): 1663
1
(γ -pyrone carbonyl group), 1701 (cyclobutane carbonyl groups). H NMR (500.1 MHz,
CDCl3): δ = 3.89 (s, 3H, OCH3), 6.72 (s, 1H, 9-H), 6.75 (d, JHH = 2.3 Hz, 1H, 3-H of
furan ring), 7.34 (s, 1H, 7-H), 7.44 (d, JHH = 2.3 Hz, 1H, 2-H of furan ring), 7.45–7.62 (m,
15H, arom-H), 7.67 (s, 1H, CH C). 13C NMR (125.8 MHz, CDCl3): δ = 60.5 (OCH3),
94.2 (C-9), 105.3 (C-3), 142.6 (C-4), 145.6 (C-2), 147.3 (C-7), 152.0 (HC C), 156.1
1
(d, JPC = 92.4 Hz, C P), 176.0 (pyrone carbonyl ring), 179.3 (CH C), 189.98 (C O
cyclobutylidene), 190.02 (C O, cyclobutylidene). 31P NMR (202.4 MHz, CDCl3): δ =
21.7. Anal. Calcd. for C35H23O6P (570.53): C, 73.68; H, 4.06; P, 5.43. Found: C, 73.60; H,
3.99; P, 5.39%.
Compound 27b: Yellow crystals; yield 70%; mp 205 ◦C (sharp). IR (ν, cm−1): 1652
1
(γ -pyrone carbonyl group), 1710 (carbonyl group). H NMR (500.1 MHz, CDCl3): δ =
3.81 (s, 3H, OCH3), 4.01 (s, 3H, OCH3), 6.76 (d, JHH = 2.3 Hz, 1H, 3-H of furan ring),
7.33 (s, 1H, 7-H), 7.38 (d, JHH = 2.3 Hz, 1H, 2-H of furan ring), 7.55–7.63 (m, 15H,
arom-H), 7.64 (s, 1H, CH C). 13C NMR (125.8 MHz, CDCl3): δ = 61.0 (OCH3), 61.5
(OCH3), 105.9 (C-3), 124.4 (C-9), 146.0 (C-2), 147.2 (C-4), 148.7 (C-7), 151.0 (HC C),
1
154.7 (d, JPC = 97.3 Hz, C P), 177.2 (pyrone carbonyl ring), 180.5 (HC C), 189.8
(C O, cyclobutylidene), 191.4 (C O, cyclobutylidene). 31P NMR (202.4 MHz, CDCl3):
δ = 21.7. Anal. Calcd. for C36H25O7P (600): C, 72.00; H, 4.20; P, 5.16. Found: C, 72.01;
H, 4.30; P, 5.28%.
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