Base-promoted one-pot sequential phosphite addition and 5- exo -dig cyclization of enynals: A facile route to trisubstituted furans

Article abstract of DOI:10.1055/s-0033-1340865

An easy route for the synthesis of trisubstituted furans has been demonstrated. One-pot sequential phosphite (H-phosphonate) addition to alkynylaldehydes (enynals) promoted by tripotassium phosphate leads to trisubstituted furans (phosphono-furans) via 5-exo-dig cyclization of the phosphono-alkynol intermediates. In contrast, in the presence of silver(I) tetrafluoroborate, the reaction using the same substrates leads to a diene product. Georg Thieme Verlag Stuttgart, New York.

Full text of DOI:10.1055/s-0033-1340865

PAPER
▌1197
paper
Base-Promoted One-Pot Sequential Phosphite Addition and 5-exo-dig
Cyclization of Enynals: A Facile Route to Trisubstituted Furans
Trisubstituted Furans via Enynals
Anasuyamma Uravakilli, Ramesh Kotikalapudi, K. C. Kumara Swamy*
School of Chemistry, University of Hyderabad, Hyderabad 500 046, A. P., India
E-mail: kckssc@uohyd.ac.in; E-mail: kckssc@yahoo.com; Fax +91(40)23012460
Received: 08.11.2013; Accepted after revision: 05.02.2014
Abstract: An easy route for the synthesis of trisubstituted furans
–O
has been demonstrated. One-pot sequential phosphite (H-phospho-
nate) addition to alkynylaldehydes (enynals) promoted by tripotas-
sium phosphate leads to trisubstituted furans (phosphono-furans)
via 5-exo-dig cyclization of the phosphono-alkynol intermediates.
In contrast, in the presence of silver(I) tetrafluoroborate, the reac-
tion using the same substrates leads to a diene product.
O–
Et
HO
N
P
O
HO
P
O
N
HO
O
O
N
O
H
H
F
+
N
H2N
Cy
Cy
2
Key words: nucleophilic addition, enynals, cyclization, isomeriza-
tion, furans, phosphorus
A
B
potent AMPK activator
[5-(4-amino-7-ethyl-5-fluoro-1-isobutyl-
1H-benzoimidazol-2-yl)furan-2-yl]-
phosphonic acid
Figure 1 Drugs containing a furylphosphonic acid moiety
The furan ring system is an important skeleton and hence
it is a much sought after target in synthetic chemistry.1 3-
Alkynylcinnamaldehydes/alcohols have been utilized for
the construction of various carbocyclic, furan, and pyran
ring systems.2 Diverse phosphono-isobenzofurans3 and
-isochromenes4 are also synthesized using o-alkynylbenz-
aldehydes. Organophosphonates, due to their enormous
application in medicinal chemistry are interesting scaf-
folds in the field of organic synthesis.5–7 As a subclass of
organophosphonates, phosphono-heterocycles have also
found many bio-related applications. For example, two
drugs containing a furylphosphonic acid moiety that can
be used for the treatment of hyperlipidemia and type 2 di-
abetes mellitus are shown in Figure 1.8 It is always chal-
lenging to introduce a phosphonate moiety on to an
aromatic ring from the synthetic perspective of arylphos-
phonates.9 Our recent investigation of the synthesis of
phosphono-furans utilizing 2-alkynylcinnamaldehydes10
resulted in the construction of phosphorus-substituted
heterocycles11 and this prompted us to find new and facile
routes for the synthesis of phosphono-furans (furylphos-
phonates). We envisaged that phosphite (H-phosphonate)
addition to 3-alkynylaldehydes followed by cyclization in
one pot could lead to phosphono-furans. Herein we report
an easy route for the construction of trisubstituted phos-
phono-furans using 3-alkynylcinnamaldehydes via one-
pot sequential phosphite (H-phosphonate) addition and
cyclization.
O
R2
R1
1g R1 = H, R2 = 3-FC6H4
1a R1 = H, R2 = Ph
1h R1 = OMe, R2 = Ph
1i R1 = OMe, R2 = 4-MeC6H4
1j R1 = F, R2 = Ph
1b R1 = H, R2 = 4-MeC6H4
1c R1 = H, R2 = 4-MeOC6H4
1d R1 = H, R2 = 4-ClC6H4
1e R1 = H, R2 = 2-O2NC6H4
1f R1 = H, R2 = 1-cyclohexenyl
1k R1 = F, R2 = 4-MeC6H4
O
O
RO
Ph
P
P
RO
H
Ph
H
2a R–R = -CH2C(Me2)CH2
2b R = Et
2d
2c R = i-Pr
Figure 2 Precursors used in this study
At the outset, the reaction of 3-alkynylaldehyde 1a and
phosphite 2a was conducted in the presence of one mole
equivalent of triethylamine in tetrahydrofuran at 50 °C
(Scheme 1, Table 1, entry 1). Interestingly, the reaction
provided furylphosphonate 3 in 65% yield. The use of di-
isopropylamine, potassium carbonate, and cesium carbon-
ate led to moderate yields of furan 3a (entries 2–4) even
after 12 hours. However, tripotassium phosphate in tetra-
hydrofuran led to the furan 3a in 81% yield at 50 °C for
four hours (entry 5). Sodium methoxide and amine bases
such as DBU, 4-(dimethylamino)pyridine, and pyridine
did not give an improved yield of 3a (entries 6–9). Even
in the presence of tripotassium phosphate, solvents such
as dioxane, toluene, and 1,2-dichloroethane gave moder-
ate yields of phosphono-furans 3a only (entries 10–12).
Thus the best conditions used one mole equivalent of tri-
potassium phosphate in tetrahydrofuran as the solvent at
Initially, diverse 3-alkynylaldehydes 1a–k were synthe-
sized from the corresponding 3-bromoacrylaldehydes and
terminal acetylenes (Figure 2).2f,12 Different H-phospho-
nates and diphenylphosphine oxide were also used in this
study.
SYNTHESIS 2014, 46, 1197–1204
Advanced online publication: 27.02.2014
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DOI: 10.1055/s-0033-1340865; Art ID: SS-2013-Z0734-OP
© Georg Thieme Verlag Stuttgart · New York

1198
A. Uravakilli et al.
PAPER
50 °C to accomplish the best yields of phosphono-furans Species I undergoes sequential 5-exo-dig cyclization and
via this route.
isomerization to lead to the furan derivative. This reaction
proceeds in one pot to afford the final product.
O
Table 2 Synthesis of Diverse Phosphorus-Containing Trisubstituted
Furans
O
CHO
O
P
O
H
O
O
base
+
Entry Alk-3-ynal Furylphosphonate
+ Phosphite
Yielda
(%)
P
O
Ph
solvent
Ph
Ph
Ph
1a
2a
3
H
Ph
Scheme 1 Reaction of 1a and 2a to form the trisubstituted phospho-
no-furan 3
O
O
1
2
3
1a + 2a
1b + 2a
1c + 2a
72
64
62
P
O
O
Table 1 Optimization for the Formation of Trisubstituted Furan 3a
3
4
Time (h) Yieldb
(%)
H
Ph
Entry
Base
Solvent
Temp
(°C)
O
O
P
O
1
2
Et3N
THF
50
50
50
50
50
50
50
50
50
50
50
50
5
5
8
5
4
5
6
6
5
5
5
5
65c
67
68c
70
81
69
64c
71
68
73
72
76
O
i-Pr2NH
K2CO3
Cs2CO3
K3PO4
NaOMe
DBU
THF
MeO
3
THF
H
Ph
4
THF
O
O
P
O
5
THF
O
6
THF
5
Cl
7
THF
H
Ph
8
DMAP
pyridine
K3PO4
K3PO4
K3PO4
THF
O
4
1d + 2a
81
P
O
9
THF
O
O
10
11
12
dioxane
toluene
DCE
6
H
Ph
O
P
5
6
7
8
1e + 2a
1f + 2a
1g + 2a
1h + 2a
84
72
92
75
O
O2N
O
a Conditions: 1a (0.5 mmol), 2a (0.6 mmol), base (0.6 mmol), solvent
(2 mL), 50 °C.
O
7
b Yield of the isolated product.
H
O
Ph
c Starting material remained.
O
P
O
O
To generalize this protocol for the synthesis of diverse
phosphorus-containing furans, with the optimized condi-
tions in hand, various 3-alkynylcinnamaldehydes 1a–k
and phosphites (H-phosphonates) 2a–c were utilized. In
all the cases furylphosphonates 3–15 were obtained in
good to excellent yields (Table 2). Diphenylphosphine ox-
ide (2d) was also used in this study to explore the reactiv-
ity of 3-alkynylcinnamaldehydes 1e and 1g, which further
led to phosphinoylfurans 16 and 17, respectively in good
yields (entries 14 and 15). The structure of 2-furylphos-
phonate 3 was confirmed by X-ray crystallography (Fig-
ure 3).13
8
H
Ph
F
O
P
O
O
O
9
H
p-anisyl
O
P
O
O
O
A probable pathway for the formation of phosphono-
furans on the basis of available literature3 is shown in
Scheme 2. Initially, the base abstracts a proton from the
phosphite (H-phosphonate) followed by nucleophilic ad-
dition to the aldehyde group of 3-alkynylcinnamaldehyde
via the Pudovik reaction14 leading to the intermediate I.
10
Synthesis 2014, 46, 1197–1204
© Georg Thieme Verlag Stuttgart · New York

PAPER
Trisubstituted Furans via Enynals
1199
Table 2 Synthesis of Diverse Phosphorus-Containing Trisubstituted
Furans (continued)
Entry Alk-3-ynal Furylphosphonate
+ Phosphite
Yielda
(%)
H
p-anisyl
O
O
9
1i + 2a
72
P
O
H
O
11
4-fluorophenyl
O
O
P
10
11
12
13
14
15
1j + 2a
1k + 2a
1a + 2b
1a + 2c
1e + 2d
1g + 2d
89
88
70
69
69
78
O
O
12
H
4-fluorophenyl
O
O
P
O
Figure 3 ORTEP of compound 3. Hydrogen atoms are omitted for
clarity. Selected bond lengths (Å): P1–C6 1.775(2), C6–C7 1.343(3),
C7–C8 1.430(3), C8–C9 1.344(3), and C9–C16 1.494(3).
O
13
14
15
H
Ph
Ph
OEt
OEt
P
O
O
O
R
R
O
R
R
BH
O
H
P
–
P
O
H
R
R
Pudovik
reaction
3-alkynyl
aldehyde
P
O–
O
+
Ph
Ph
O-i-Pr
O-i-Pr
[base]
B
P
Ph
Ph
BH+
O
I
5-exo-dig
cyclization
H
Ph
R
R
R
O
Ph
O
O
R
R
P
P
R
P
P
O
Ph
O2N
O
isomerization
O
O
O
– B
16
Ph
Ph
Ph
BH+
H
Ph
Ph
Ph
–
Ph
H
II
III
F
Ph
Ph
P
O
Scheme 2 Plausible pathway for the formation of furans
O
17
a Yield of the isolated product.
O
O
O
There is a precedent for the metal-catalyzed reaction of al-
kynylaldehydes and phosphites leading to pyran deriva-
tives.4a Hence reaction of 1a with 2a was performed in the
presence of catalytic silver(I) tetrafluoroborate (Scheme
3). The reaction leads to the phosphono-diene 18 (X-ray,13
Figure 4); it is likely that the initially formed pyran IV un-
dergoes ring opening to form the diene 18.
O
P
O
O
P
AgBF4
DCE
1a + 2a
O
O
Ph
18
Ph
Ph
Ph
IV
Scheme 3 Formation of phosphono diene
In conclusion, a new and facile synthetic route to trisub-
stituted furans with phosphono- or phosphinoyl-substitu-
ents has been demonstrated. This reaction involves the
one-pot synthesis of diverse trisubstituted furans in good
yields starting from 3-alkynylaldehydes and H-phospho-
nates.
© Georg Thieme Verlag Stuttgart · New York
Synthesis 2014, 46, 1197–1204

1200
A. Uravakilli et al.
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1H NMR (400 MHz, CDCl3): δ = 10.41 (d, J = 7.6 Hz, 1 H), 7.87–
7.85 (m, 2 H), 7.57–7.48 (m, 5 H), 6.95 and 6.93 (2 br s, 2 H), 6.78
(d, J = 8.4 Hz, 1 H), 3.90 (s, 3 H, ArOCH3).
13C NMR (100 MHz, CDCl3): δ = 193.3, 160.9, 143.0, 135.9, 133.7,
131.0, 130.3, 128.9, 127.2, 114.4, 113.7, 102.9, 83.6, 55.4.
LC-MS: m/z = 263 [M + 1]+.
Anal. Calcd for C18H14O2: C, 82.42; H, 5.38. Found: C, 82.31; H,
5.45.
(Z)-5-(4-Chlorophenyl)-3-phenylpent-2-en-4-ynal (1d)
Orange gummy liquid; yield: 109 mg (82%).
IR (neat): 3408, 3057, 1719, 1659 cm–1.
1H NMR (400 MHz, CDCl3): δ = 10.40 (d, J = 8.0 Hz, 1 H), 7.85–
7.83 (m, 2 H), 7.55–7.39 (m, 7 H), 6.82 (d, J = 8.0 Hz, 1 H).
Figure 4 ORTEP of compound 18. Hydrogen atoms are omitted for
clarity. Selected bond lengths (Å): P1–C6 1.774(2), C6–C7 1.334(3),
C7–C8 1.464(3), C8–C15 1.349(3), and C15–C16 1.476(3).
13C NMR (100 MHz, CDCl3): δ = 193.1, 142.3, 136.1, 135.6, 133.2,
131.2, 129.8, 129.1, 128.9, 127.2, 120.1, 100.9, 85.1.
Solvents were dried according to known methods as appropriate.15
1H, 13C, and 31P NMR spectra (1H: 400 MHz or 500 MHz; 13C: 100
MHz or 125 MHz; 31P: 162 MHz) were recorded using a 400 MHz
or 500 MHz spectrometer in CDCl3 (unless stated otherwise) with
shifts referenced to TMS (δ = 0 ppm) or 85% H3PO4 (δ = 0 ppm).
IR spectra were recorded on an FT-IR spectrophotometer. Melting
points were determined by using a local hot-stage melting point ap-
paratus and are uncorrected. Elemental analyses were carried out on
a CHN analyzer. Mass spectra were recorded using an LCMS in-
strument. HRMS were performed using a mass spectrometer
Bruker-maXis with ESI-QTOF-II method. Single crystal X-ray dif-
fraction was collected on Oxford diffractometer using MoKα
(l = 0.71073 Å) radiation. The structure was solved and refined by
standard methods.15
LC-MS: m/z = 267, 269 [M]+ [M + 2]+.
Anal. Calcd for C17H11OCl: C, 76.55; H, 4.16. Found: C, 76.65; H,
4.23.
(Z)-5-(2-Nitrophenyl)-3-phenylpent-2-en-4-ynal (1e)
Yellow solid; yield: 126 mg (91%); mp 95–97 °C.
IR (KBr): 3063, 1720, 1659, 1555 cm–1.
1H NMR (400 MHz, CDCl3): δ = 10.45 (m, J = 6.8 Hz, 1 H), 8.22
(d, J = 8.0 Hz, 1 H), 7.92–7.27 (m, 8 H), 6.89 (m, J = 6.8 Hz, 1 H).
13C NMR (100 MHz, CDCl3): δ = 193.0, 149.1, 141.5, 135.2, 135.0,
133.4, 132.6, 131.3, 130.2, 127.3, 125.2, 117.4, 96.3, 91.1.
LC-MS: m/z = 278 [M + 1]+.
Anal. Calcd for C17H11O3N: C, 73.64; H, 4.00; N, 5.05. Found: C,
73.48; H, 4.08; N, 5.12.
3-Bromoacrylaldehydes were synthesized by following a literature
procedure.12
(Z)-5-Cyclohex-1-enyl-3-phenylpent-2-en-4-ynal (1f)
(Z)-3,5-Diarylpent-2-en-4-ynals 1a–k; General Procedure
Yellow oil; yield: 96 mg (82%).
These precursors were synthesized by slightly modifying a litera-
ture procedure.2f To
a
stirred solution of (Z)-3-aryl-3-
IR (neat): 3413, 3063, 1725, 1665 cm–1.
bromoacrylaldehyde11 (5.00 mmol) in MeCN (16 mL) were added
Et3N (1 mL), PdCl2 (0.026 g, 0.15 mmol), Ph3P (0.079 g, 0.30
mmol), CuI (0.057 g, 0.30 mmol), and terminal acetylene (6.00
mmol) at r.t. and the mixture was stirred for a further 1 h. After com-
pletion of the reaction, sat. NH4Cl soln (30 mL) was added and the
mixture was extracted with Et2O (3 × 50 mL). The combined organ-
ic layers were stripped of volatiles under vacuum. The crude prod-
uct was purified by column chromatography (silica gel, hexane–
EtOAc, 10:1). Compound 1a is known but 1b–k are new; spectro-
scopic data for 1a are identical to that known in the literature.2f
1H NMR (400 MHz, CDCl3): δ = 10.29 (d, J = 8.0 Hz, 1 H), 7.80–
7.78 (m, 2 H), 7.45–7.44 (m, 3 H), 6.72 (d, J = 8.0 Hz, 1 H), 6.41 (s,
1 H, Hcyclohexenyl), 2.28 and 2.20 (2 br s, 4 H), 1.72–1.60 (m, 4 H).
13C NMR (100 MHz, CDCl3): δ = 193.5, 143.1, 138.9, 135.8, 130.9,
130.2, 128.8, 127.1, 120.2, 104.7, 82.1, 28.8, 26.0, 22.1, 21.2.
LC-MS: m/z = 237 [M + 1]+.
Anal. Calcd for C17H16O: C, 86.40; H, 6.82. Found: C, 86.27; H,
6.71.
(Z)-5-(3-Fluorophenyl)-3-phenylpent-2-en-4-ynal (1g)
(Z)-5-(4-Methylphenyl)-3-phenylpent-2-en-4-ynal (1b)
Yellow solid; yield: 117 mg (89%); mp 146–148 °C.
Orange liquid; yield: 109 mg (89%).
IR (KBr): 3057, 1657, 1579, 1221 cm–1.
1H NMR (400 MHz, CDCl3): δ = 10.40 (d, J = .8.0 Hz, 1 H), 7.85–
7.83 (m, 2 H), 7.50–7.15 (m, 7 H), 6.83 (d, J = 8.0 Hz, 1 H).
13C NMR (100 MHz, CDCl3): δ = 193.6, 163.2, 159.5, 143.4, 135.3,
132.2, 131.6, 130.7, 130.1, 129.6, 129.1, 128.6, 128.5, 122.6, 115.7,
99.3, 85.5.
IR (neat): 3419, 1764, 1666 cm–1.
1H NMR (400 MHz, CDCl3): δ = 10.42 (d, J = 8.0 Hz, 1 H), 7.88–
7.86 (m, 2 H), 7.52–7.48 (m, 5 H), 7.24 and 7.22 (2 br s, 2 H), 6.80
(d, J = 8.0 Hz, 1 H), 2.42 (s, 3 H, ArCH3).
13C NMR (100 MHz, CDCl3): δ = 193.4, 142.9, 140.4, 135.7, 132.0,
131.1, 130.7, 129.5, 128.9, 127.2, 118.6, 102.8, 83.9, 21.7.
LC-MS: m/z = 249 [M + 1]+.
LC-MS: m/z = 247 [M + 1]+.
Anal. Calcd for C17H11OF: C, 81.59; H, 4.43. Found: C, 81.46; H,
4.51.
Anal. Calcd for C18H14O: C, 87.78; H, 5.73. Found: C, 87.69; H,
5.78.
(Z)-3-(4-Methoxyphenyl)-5-phenylpent-2-en-4-ynal (1h)
(Z)-5-(4-Methoxyphenyl)-3-phenylpent-2-en-4-ynal (1c)
Bright yellow solid; yield: 115 mg (88%); mp 68–70 °C.
Orange gummy liquid; yield: 114 mg (87%).
IR (KBr): 3287, 2860, 1668, 1569 cm–1.
IR (neat): 3386, 3063, 1770, 1720, 1665 cm–1.
1H NMR (400 MHz, CDCl3): δ = 10.41 (d, J = 7.6 Hz, 1 H), 7.87–
7.85 (m, 2 H), 7.57–7.47 (m, 5 H), 6.95–6.93 (m, 2 H), 6.78 (d,
J = 8.4 Hz, 1 H), 3.90 (s, 3 H, OCH3).
Synthesis 2014, 46, 1197–1204
© Georg Thieme Verlag Stuttgart · New York

PAPER
Trisubstituted Furans via Enynals
1201
13C NMR (100 MHz, CDCl3): δ = 193.2, 161.0, 143.0, 135.9, 133.7,
131.0, 130.33, 130.30, 128.9, 127.2, 114.4, 103.0, 83.6, 55.4.
LC-MS: m/z = 263 [M + 1]+.
13C NMR (100 MHz, CDCl3): δ = 155.0 (d, 3JP-C = 9.0 Hz, PCOC),
1
142.5 (d, JP-C = 242.0 Hz, PC), 137.1, 132.2, 128.8, 128.7, 128.5,
2
127.9, 127.4, 126.7, 124.4 (d, JP-C = 25.0 Hz, PC=C), 123.4 (d,
3JP-C = 11.0 Hz, PC=C-C), 77.0 (s, OCH2), 33.3 (s, PhCH2), 32.3 [d,
3JP-C = 6.8 Hz, C(CH3)2], 21.8 and 20.8 [2 s, C(CH3)2].
Anal. Calcd for C18H14O2: C, 82.42; H, 5.38.Found: C, 82.56; H,
5.31.
31P NMR: δ = –3.10.
HRMS (ESI): m/z [M + H]+ calcd for C22H24O4P: 383.1411; found:
383.1412.
(Z)-3-(4-Methoxyphenyl)-5-(4-methylphenyl)pent-2-en-4-ynal
(1i)
Yellow gummy solid; yield: 120 mg (86%); mp 72–74 °C.
IR (KBr): 3030, 2997, 1660, 1594 cm–1.
5-(5,5-Dimethyl-2-oxo-1,3,2-dioxaphosphinan-2-yl)-2-(4-meth-
ylbenzyl)-3-phenylfuran (4)
1H NMR (400 MHz, CDCl3): δ = 10.40 (m, J = 6.0 Hz, 1 H), 7.50–
7.38 (m, 5 H), 7.24–7.21 (m, 2 H), 7.03 (d, J = 8.0 Hz, 1 H), 6.78
(m, J = 5.6 Hz, 1 H), 3.90 (s, 3 H, OCH3), 2.40 (s, 3 H, CH3).
13C NMR (100 MHz, CDCl3): δ = 193.3, 159.9, 142.6, 140.4, 137.1,
132.0, 130.8, 129.5, 119.7, 116.7, 112.7, 102.7, 83.9, 55.4, 21.7.
Pale yellow solid; yield: 126 mg (64%); mp 170–172 °C.
IR (KBr): 3123, 3052, 2964, 2888, 1605, 1578, 1534, 1468, 1348,
1277, 1112, 1058, 1008, 986, 833, 767, 707, 553, 477 cm–1.
1H NMR (400 MHz, CDCl3): δ = 7.42–7.11 (m, 10 H, HAr), 4.15 (s,
2 H, PhCH2), 4.10–4.01 (m, 4 H, OCH2), 2.32 (s, 3 H, ArCH3), 1.24
and 0.95 [2 s, 6 H, C (CH3)2].
LC-MS: m/z = 277 [M + 1]+.
13C NMR (100 MHz, CDCl3): δ = 155.4 (d, 3JP-C = 10.0 Hz, PCOC),
Anal. Calcd for C19H16O2: C, 82.58; H, 5.84. Found: C, 82.41; H,
5.81.
1
142.4 (d, JP-C = 242.0 Hz, PC), 136.3, 132.3, 132.2, 129.4, 129.1,
128.4, 127.9, 127.4, 124.4 (d, 2JP-C = 27.0 Hz, PC=C), 123.2 (d, 3JP-
C = 12.0 Hz, PC=C-C), 77.1 (s, OCH2), 32.9 (s, PhCH2), 32.3 [d, 3JP-
C = 7.0 Hz, C(CH3)2], 21.8, 21.0 and 20.7 [3 s, C(CH3)2 + ArCH3].
(Z)-3-(4-Fluorophenyl)-5-phenylpent-2-en-4-ynal (1j)
Yellow solid; yield: 111 mg (89%); mp 145–147 °C.
IR (KBr): 3063, 1659, 1572, 1183 cm–1.
1H NMR (400 MHz, CDCl3): δ = 10.40 (d, J = 8 Hz, 1 H), 7.88–
7.84 (m, 2 H), 7.62–7.59 (m, 2 H), 7.47–7.40 (m, 3 H), 7.19–7.15
(m, 2 H), 6.75 (d, J = 8 Hz, 1 H).
31P NMR: δ = –2.91.
HRMS (ESI): m/z [M + H]+ calcd for C23H26O4P: 397.1569; Found:
397.1569.
13C NMR (100 MHz, CDCl3): δ = 193.6, 163.2, 159.5, 143.4, 135.3,
132.7, 131.6, 130.1, 129.3, 128.6, 122.7, 122.5, 115.8, 99.3, 85.5.
LC-MS: m/z = 249 [M + 1]+.
5-(5,5-Dimethyl-2-oxo-1,3,2-dioxaphosphinan-2-yl)-2-(4-meth-
oxybenzyl)-3-phenylfuran (5)
Pale yellow solid; yield: 128 mg (62%); mp 150–152 °C.
IR (KBr): 2959, 2932, 2827, 1742, 1611, 1507, 1277, 1244, 1178,
1101, 1058, 1003, 838, 784, 701, 542 cm–1.
1H NMR (400 MHz, CDCl3): δ = 7.43–6.85 (m, 10 H, HAr), 4.12–
4.08 (m, 6 H, OCH2 + PhCH2), 3.81 (s, 3 H, OCH3), 1.26 and 0.98
[2 s, 6 H, C(CH3)2].
Anal. Calcd for C17H11OF: C, 81.59; H, 4.43. Found: C, 81.42; H,
4.38.
(Z)-3-(4-Fluorophenyl)-5-(4-methylphenyl)pent-2-en-4-ynal
(1k)
Orange gummy liquid; yield: 114 mg (72%).
13C NMR (100 MHz, CDCl3): δ = 158.4 (C-OCH3), 155.6 (d, 3JP-C
=
IR (neat): 3047, 1671, 1600, 1342 cm–1.
1
9.0 Hz, PCOC), 142.3 (d, JP-C = 252.0 Hz, PC), 132.2, 129.5,
129.1, 128.4, 127.8, 127.4, 124.5 (d, 2JP-C = 25.0 Hz, PC=C), 123.1
1H NMR (400 MHz, CDCl3): δ = 10.39 (d, J = 8.0 Hz, 1 H), 7.88–
7.84 (m, 2 H), 7.50–7.49 (m, 2 H), 7.27–7.14 (m, 4 H), 6.73 (d,
J = 8.0 Hz, 1 H), 2.41 (s, 3 H, CH3).
13C NMR (100 MHz, CDCl3): δ = 193.2, 164.5, 141.6, 140.6, 132.0,
131.9, 131.8, 130.3, 129.5, 129.4, 129.3, 118.4, 116.0, 103.0, 83.6,
21.7.
3
(d, JP-C = 12.0 Hz, PC=C-C), 114.1, 77.1 (s, OCH2), 55.3 (s,
OCH3), 32.4 (s, PhCH2), 32.3 [d, 3JP-C = 7.0 Hz, C(CH3)2], 21.8 and
20.8 [2 s, C(CH3)2].
31P NMR: δ = –2.90.
HRMS (ESI): m/z [M + H]+ calcd for C23H26O5P: 413.1519; found:
LC-MS: m/z = 265 [M + 1]+.
413.1519.
Anal. Calcd for C18H13OF: C, 81.80; H, 4.96. Found: C, 81.68; H,
4.85.
2-(4-Chlorobenzyl)-5-(5,5-dimethyl-2-oxo-1,3,2-dioxaphosphi-
nan-2-yl)-3-phenylfuran (6)
Pale yellow solid; yield: 170 mg (81%); mp 110–112 °C.
2,3-Disubstituted 5-Phosphono- or 5-Phosphinoylfurans 3–17;
General Procedure
IR (KBr): 3107, 3052, 2964, 2888, 1742, 1600, 1490, 1282, 1058,
1014, 816, 784, 690, 548 cm–1.
1H NMR (400 MHz, CDCl3): δ = 7.43–7.13 (m, 10 H, HAr), 4.16 (s,
2 H, PhCH2), 4.13–4.06 (m, 4 H, OCH2), 1.23 and 0.97 [2 s, 6 H, C
(CH3)2].
To a stirred solution of H-phosphonate (0.6 mmol) and K3PO4 (0.6
mmol) in THF (1 mL) was added 3-alkynylcinnamaldehyde (0.5
mmol) in THF (1 mL) under a N2 atmosphere. The solution was
stirred at 50 °C until the starting material had been consumed. Sol-
vent was removed under vacuum and the crude product was purified
by column chromatography (silica gel, hexane–EtOAc, 1:1).
13C NMR (100 MHz, CDCl3): δ = 154.4 (d, 3JP-C = 7.0 Hz, PCOC),
1
142.5 (d, JP-C = 194.0 Hz, PC), 135.5, 132.6, 132.0, 129.8, 128.9,
2
128.8, 127.8, 127.5, 124.5 (d, JP-C = 19.0 Hz, PC=C), 123.6 (d,
2-Benzyl-5-(5,5-dimethyl-2-oxo-1,3,2-dioxaphosphinan-2-yl)-3-
phenylfuran (3)
Pale yellow solid; yield: 137 mg (72%); mp 168–170 °C.
3JP-C = 8.0 Hz, PC=C-C), 77.05 and 77.00 (2 s, OCH2), 32.7 (s,
3
PhCH2), 32.3 [d, JP-C = 6.0 Hz, C(CH3)2], 21.8 and 20.8 [2 s,
C(CH3)2].
31P NMR: δ = –3.02.
IR (KBr): 3084, 3052, 3030, 2964, 2899, 2866, 1605, 1518, 1496,
1282, 1244, 1151, 1101, 1052, 1008, 975, 773, 729, 548 cm–1.
HRMS (ESI): m/z [M + H]+ and [M + 2 + H]+ calcd for
C22H23O4ClP: 417.1023; found: 417.1021 and 419.0997.
1H NMR (400 MHz, CDCl3): δ = 7.43–7.22 (m, 11 H, HAr), 4.21 (s,
2 H, PhCH2), 4.11–4.05 (m, 4 H, OCH2), 1.25 and 0.95 [2 s, 6 H,
C(CH3)2].
© Georg Thieme Verlag Stuttgart · New York
Synthesis 2014, 46, 1197–1204

1202
A. Uravakilli et al.
PAPER
5-(5,5-Dimethyl-2-oxo-1,3,2-dioxaphosphinan-2-yl)-2-(2-nitro-
benzyl)-3-phenylfuran (7)
Pale yellow solid; yield: 180 mg (84%); mp 108–110 °C.
1H NMR (400 MHz, CDCl3): δ = 7.35–6.87 (m, 10 H, HAr), 4.20 (s,
2 H, PhCH2), 4.12–4.01 (m, 4 H, OCH2), 3.77 (s, 3 H, OCH3), 1.23
and 0.91 [2 s, 6 H, C(CH3)2].
3
13C NMR (100 MHz, CDCl3): δ = 159.9, 155.2 (d, JP-C = 9.0 Hz,
IR (KBr): 2959, 1611, 1529, 1342, 1266, 1112, 1052, 1008, 975,
833, 789, 729, 701, 553 cm–1.
1H NMR (400 MHz, CDCl3): δ = 8.02–7.17 (m, 10 H, HAr), 4.58 (s,
2 H, PhCH2), 4.11–4.00 (m, 4 H, OCH2), 1.24 and 0.94 [2 s, 6 H,
C(CH3)2].
PCOC), 142.5 (d, 1JP-C = 241.5 Hz, PC), 137.1, 133.5, 129.9, 128.7,
128.5, 126.7, 124.4 (d, JP-C = 24.4 Hz, PC=C), 123.3 (d, JP-C
11.0 Hz, PC=C-C), 120.2, 113.4, 113.1, 77.1 (s, OCH2), 55.2 (s,
OCH3), 33.4 (s, PhCH2), 32.3 [d, 3JP-C = 6.7. Hz, C(CH3)2], 21.8 and
20.8 [2 s, C(CH3)2].
2
3
=
13C NMR (100 MHz, CDCl3): δ = 152.8 (d, 3JP-C = 7.0 Hz, PCOC),
31P NMR: δ = –3.10.
149.0, 143.2 (d, 1JP-C = 193.0 Hz, PC), 133.5, 132.0, 131.8, 131.7,
128.9, 128.1, 127.8, 127.7, 125.0, 124.52 (d, 2JP-C = 20.0 Hz, PC=C),
HRMS (ESI): m/z [M + H]+ calcd for C23H26O5P: 413.1519; found:
3
124.50 (s, PC=C-C), 77.2 and 77.1 (2 s, OCH2), 32.3 [d, JP-C
6.0 Hz, C(CH3)2], 30.7 (s, PhCH2), 21.8 and 20.7 [2 s, C(CH3)2].
=
413.1520.
5-(5,5-Dimethyl-2-oxo-1,3,2-dioxaphosphinan-2-yl)-3-(4-meth-
oxyphenyl)-2-(4-methylbenzyl)furan (11)
Pale yellow gummy solid; yield: 155 mg (72%).
31P NMR: δ = –3.60.
HRMS (ESI): m/z [M + H]+ calcd for C22H23O6PN: 428.1266;
found: 428.1263.
IR (neat): 2967, 1764, 1605, 1573, 1512, 1463, 1430, 1367, 1282,
1216, 1162, 1058, 1008, 838, 789 cm–1.
1H NMR (400 MHz, CDCl3): δ = 7.35–6.86 (m, 9 H, HAr), 4.17–
4.02 (m, 6 H, OCH2, PhCH2), 3.80 (s, 3 H, OCH3), 2.32 (s, 3 H,
CH3), 1.25 and 0.95 [2 s, 6 H, C(CH3)2].
2-(Cyclohex-1-enylmethyl)-5-(5,5-dimethyl-2-oxo-1,3,2-dioxa-
phosphinan-2-yl)-3-phenylfuran (8)
Pale yellow solid; yield: 137 mg (72%); mp 140–142 °C.
IR (KBr): 2921, 1611, 1468, 1364, 1293, 1249, 1096, 1008, 832,
783, 706, 542 cm–1.
1H NMR (400 MHz, CDCl3): δ = 7.43–7.32 (m, 6 H, HAr), 5.47 (s,
1 H, =CH), 4.25–4.11 (m, 4 H, OCH2), 3.45 (s, 2 H, CH2), 2.00–1.93
and 1.62–1.56 (m, 8 H, Hcyclohexenyl), 1.28 and 1.06 [2 s, 6 H,
C(CH3)2].
3
13C NMR (100 MHz, CDCl3): δ = 159.9, 155.5 (d, JP-C = 9.1 Hz,
PCOC), 142.4 (d, 1JP-C = 241.8 Hz, PC), 136.4, 134.1, 133.7, 129.9,
2
3
129.4, 128.5, 124.4 (d, JP-C = 24.5 Hz, PC=C), 123.1 (d, JP-C
=
11.1 Hz, PC=C-C), 120.3, 113.5, 113.1, 77.1 (s, OCH2), 55.3 (s,
OCH3), 33.0 (s, PhCH2), 32.3 [d, 3JP-C = 6.7.Hz, C(CH3)2], 21.9 (s,
CH3), 21.1 and 20.8 [2 s, C (CH3)2].
31P NMR: δ = –3.0.
HRMS (ESI): m/z [M + H]+ calcd for C24H28O5P: 427.1675; found:
427.1676.
13C NMR (100 MHz, CDCl3): δ = 155.7 (d, 3JP-C = 8.0 Hz, PCOC),
1
141.8 (d, JP-C = 194.0 Hz, PC), 133.7, 132.5, 128.7, 127.9, 127.2,
124.4 (2JP-C = 20.0 Hz, PC=C), 124.1, 123.4 (d, JP-C = 9.0 Hz,
3
3
PC=C-C), 77.1 (s, OCH2), 35.7 (s, CH2), 32.4 [d, JP-C = 5.0 Hz,
C(CH3)2], 28.6, 25.3, 22.8, 22.2, 21.9 and 20.9 [6 s, C(CH3)2,
C
cyclohexenyl].
2-Benzyl-5-(5,5-dimethyl-2-oxo-1,3,2-dioxaphosphinan-2-yl)-3-
(4-fluorophenyl)furan (12)
31P NMR: δ = –2.40.
HRMS (ESI): m/z [M + H]+ calcd for C22H28O4P: 387.1726; found:
Bright yellow solid; yield: 178 mg (89%); mp 140–142 °C.
IR (KBr): 3112, 3058, 2970, 2893, 1600, 1578, 1518, 1501, 1375,
1282, 1227, 1123, 1063, 1014, 953, 920, 833, 773, 718, 603, 548
cm–1.
1H NMR (400 MHz, CDCl3): δ = 7.34–7.08 (m, 10 H, HAr), 4.16 (s,
2 H, PhCH2), 4.09–4.05 (m, 4 H, OCH2), 1.24 and 0.95 [2 s, 6 H, C
(CH3)2].
387.1723.
5-(5,5-Dimethyl-2-oxo-1,3,2-dioxaphosphinan-2-yl)-2-(3-fluo-
robenzyl)-3-phenylfuran (9)
Bright yellow solid; yield: 185 mg (92%); mp 122–124 °C.
IR (KBr): 3107, 3052, 2975, 2899, 1616, 1589, 1512, 1490, 1441,
1375, 1288, 1244, 1129, 1101, 1047, 1003, 866, 827, 784, 712, 613,
553 cm–1.
1H NMR (400 MHz, CDCl3): δ = 7.45–6.92 (m, 10 H, HAr), 4.19 (s,
2 H, PhCH2), 4.11 and 4.08 (2 br s, 4 H, OCH2), 1.24 and 0.98 [2 s,
6 H, C (CH3)2].
13C NMR (100 MHz, CDCl3): δ = 162.2 (d, 1JF-C = 245.0 Hz, FC),
3
1
155.0 (d, JP-C = 9.0 Hz, PCOC), 142.6 (d, JP-C = 242.0 Hz, PC),
137.0, 129.6 (d, 3JF-C = 8.0 Hz, FC=C), 128.8, 128.5, 128.3, 128.2,
126.9, 124.3 (d, 2JP-C = 24.0 Hz, PC=C), 122.5 (d, 3JP-C = 11.0 Hz,
2
PC=C-C), 115.8 (d, JF-C = 22.0 Hz, FC=C), 77.14 and 77.10 (2 s,
OCH2), 33.2 (s, PhCH2), 32.3 [d, 3JP-C = 7.0 Hz, C(CH3)2], 21.8 and
20.8 [2 s, C(CH3)2].
13C NMR (100 MHz, CDCl3): δ = 162.9 (d, 1JF-C = 245.0 Hz, FC),
154.2 (d, 3JP-C = 10.0 Hz, PCOC), 142.7 (d, 1JP-C = 242.0 Hz, PC),
31P NMR: δ = –3.20.
HRMS (ESI): m/z [M + H]+ calcd for C22H23FO4P: 401.1319; found:
3
3
139.6 (d, JF-C = 8.0 Hz, FC=C), 132.0, 130.2 (d, JF-C = 9.0 Hz,
FC=C), 128.9, 127.9, 127.6, 124.5 (d, JP-C = 25.0 Hz, PC=C),
2
3
124.22, 124.20, 123.7 (d, JP-C = 11.0 Hz, PC=C-C), 115.5 and
401.1317.
113.7 (2 d, 2JF-C = 21.0 Hz each, FC=C), 77.3 and 77.1 (2 s, OCH2),
33.0 (s, PhCH2), 32.3 [d, 3JP-C = 7.0 Hz, C(CH3)2], 21.8 and 20.8 [2
s, C(CH3)2].
5-(5,5-Dimethyl-2-oxo-1,3,2-dioxaphosphinan-2-yl)-3-(4-fluo-
rophenyl)-2-(4-methylbenzyl)furan (13)
Bright yellow solid; yield: 186 mg (88%); mp 128–130 °C.
31P NMR: δ = –3.10.
HRMS (ESI): m/z [M + H]+ calcd for C22H23O4FP: 401.1319; found:
IR (KBr): 3090, 2964, 2926, 2893, 1600, 1583, 1523, 1495, 1468,
1375, 1287, 1227, 1145, 1112, 1063, 1013, 980, 958, 920, 827, 778,
602, 542, 482 cm–1.
401.1320.
2-Benzyl-5-(5,5-dimethyl-2-oxo-1,3,2-dioxaphosphinan-2-yl)-3-
(4-methoxyphenyl)furan (10)
Yellow solid; yield: 155 mg (75%); mp 94–96 °C.
1H NMR (400 MHz, CDCl3): δ = 7.34–7.07 (m, 9 H, HAr), 4.11–
4.03 (m, 6 H, OCH2, PhCH2), 2.33 (s, 3 H, CH3), 1.25 and 0.96 [2
s, 6 H, C(CH3)2].
13C NMR (100 MHz, CDCl3): δ = 162.2 (d, 1JF-C = 197.0 Hz, FC),
IR (KBr): 3101, 2959, 2893, 1770, 1600, 1468, 1392, 1288, 1255,
1058, 1014, 948, 795, 723, 706, 559, 482 cm–1.
3
1
155.3 (d, JP-C = 7.0 Hz, PCOC), 142.5 (d, JP-C = 193.0 Hz, PC),
136.4, 133.9, 129.5 (d, 3JF-C = 7.0 Hz, FC=C), 129.4, 128.3, 124.3
2
3
(d, JP-C = 19.0 Hz, PC=C), 122.3 (d, JP-C = 9.0 Hz, PC=C-C),
Synthesis 2014, 46, 1197–1204
© Georg Thieme Verlag Stuttgart · New York

PAPER
Trisubstituted Furans via Enynals
1203
115.8 (d, 2JF-C = 17.0 Hz, FC=C), 77.0 (s, OCH2), 32.8 (s, PhCH2),
32.3 [d, 3JP-C = 7.0 Hz, C(CH3)2], 21.8 (s, CH3), 21.0 and 20.8 [2 s,
C(CH3)2].
31P NMR: δ = –3.10.
HRMS (ESI): m/z [M + H]+ calcd for C23H25O4FP: 415.1475; found:
13C NMR (100 MHz, CDCl3): δ = 162.9 (d, 1JF-C = 196.0 Hz, FC),
3
1
155.2 (d, JP-C = 5.0 Hz, PCOC), 146.8 (d, JP-C = 108.0 Hz, PC),
139.9 (d, 3JF-C = 6.0 Hz, FC=C), 133.0, 132.9, 132.8, 132.4, 132.3,
132.2, 131.9, 131.8, 131.7, 131.6, 131.5, 131.0, 130.1 (d, 3JF-C = 6.0
Hz, FC=C), 128.9, 128.8, 128.6 (d, 3JP-C = 11. 0 Hz, PC=C), 128.0,
2
127.9, 127.5, 124.9 (d, JP-C = 14.0 Hz, PC=C-C), 124.1, 124.0,
115.3 and 113.6 (2 d, each 2JF-C = 17.0 Hz, FC=C), 32.8 (s, ArCH2).
31P NMR: δ = 16.00.
415.1472.
Diethyl 5-Benzyl-4-phenylfuran-2-ylphosphonate (14)
Light yellow gummy liquid; yield: 130 mg (70%).
HRMS (ESI): m/z [M + H]+ calcd for C29H23O2FP: 453.1420; found:
453.1418.
IR (neat): 3057, 3030, 2975, 2926, 2904, 1764, 1600, 1490, 1452,
1392, 1255, 1101, 1019, 975, 767, 729, 696 cm–1.
5,5-Dimethyl-2-[(E,E)-5-oxo-3,5-diphenylpentyl]-1,3,2-dioxa-
phosphinan-2-one (18)
1H NMR (400 MHz, CDCl3): δ = 7.40–7.18 (m, 11 H, HAr), 4.19–
4.12 (m, 6 H, OCH2, PhCH2), 1.31 (t, 3JH-H = 7.0 Hz, 6 H, CH3CH2).
A mixture of the H-phosphonate 2a (0.5 mmol), 3-alkynylcinnam-
aldehyde 1a (g, 0.5 mmol), and AgBF4 (0.05 mmol, 10 mol%) in
DCE (2 mL) was stirred overnight at r.t. under a N2 atmosphere. Af-
ter completion of the reaction, the mixture was quenched with H2O
(2 mL) and extracted with EtOAc. Solvent was removed under vac-
uum and the crude product 18 was purified by column chromatog-
raphy (silica gel, hexane–EtOAc, 1:1) to give a bright yellow solid;
yield: 180 mg (95%); mp 128–130 °C.
13C NMR (100 MHz, CDCl3): δ = 155.2 (d, 3JP-C = 9.2 Hz, PCOC),
1
142.3 (d, JP-C = 241.1 Hz, PC), 137.4, 132.4, 128.8, 128.6, 128.3,
2
127.8, 127.4, 126.7, 124.6 (d, JP-C = 24.2 Hz, PC=C), 123.6 (d,
2
3JP-C = 10.7 Hz, PC=C-C), 62.9 (d, JP-C = 5.1 Hz, OCH), 33.1 (s,
PhCH2), 16.2 (d, 3JP-C = 6.4 Hz, CH3CH2).
31P NMR: δ = 4.31.
HRMS (ESI): m/z [M + H]+ calcd for C21H24O4P: 371.1413; found:
371.1410.
IR (KBr): 3030, 2975, 2937, 2877, 1655, 1605, 1551, 1474, 1441,
1359, 1277, 1222, 1058, 1008, 942, 838, 778, 701, 619, 553 cm–1.
2
3
1H NMR (500 MHz, CDCl3): δ = 8.19 (dd→t, JP-H ~ JH-H = 20.0
Hz, 1 H, P-CH), 7.98 (m, 2 H), 7.60–7.45 (m, 8 H), 7.13 (s, 1 H),
5.93 (dd→t, 3JP-H ~ 3JH-H = 19.0 Hz, 1 H, PC=CH), 4.12–4.08 (m, 4
H), 1.24 and 1.03 [2 s, 6 H, C (CH3)2].
Diisopropyl 5-Benzyl-4-phenylfuran-2-ylphosphonate (15)
Pale yellow gummy liquid; yield: 138 mg (69%).
IR (neat): 3057, 3024, 2980, 2931, 1757, 1605, 1495, 1457, 1391,
1260, 1100, 986, 772, 728, 690 cm–1.
1H NMR (400 MHz, CDCl3): δ = 7.40–7.18 (m, 11 H, HAr), 4.72–
4.67 (m, 2 H, OCH), 4.18 (s, 2 H, PhCH2), 1.36 and 1.23 (2 d, each
4JP-H = 7.2 Hz, 12 H, CH3).
13C NMR (100 MHz, CDCl3): δ = 190.7, 155.7 (d, 2JP-C = 20.0 Hz,
PCCH), 145.5 (d, JP-C = 6.0 Hz, PCCCH), 138.3, 133.3, 129.1,
128.9, 128.8, 128.7, 128.6, 127.3, 123.1 (d, JP-C = 144.0 Hz, PC),
77.3 and 77.1 (2 s, OCH2), 32.6 [d, JP-C = 5.0 Hz, C(CH3)2], 21.9
3
1
3
13C NMR (100 MHz, CDCl3): δ = 154.9 (d, 3JP-C = 9.0 Hz, PCOC),
and 21.1 [2 s, C(CH3)2].
31P NMR: δ = 11.70.
1
143.5 (d, JP-C = 241.0 Hz, PC), 137.5, 132.5, 128.8, 128.6, 128.3,
2
127.8, 127.2, 126.6, 124.1 (d, JP-C = 24.0 Hz, PC=C), 123.5 (d,
3JP-C = 11.0 Hz, PC=C-C), 71.8 (d, JP-C = 5.0, OCH), 33.1 (s,
HRMS (ESI): m/z [M + H]+ calcd for C22H24O4P: 383.1411; found:
2
PhCH2), 24.0 and 23.7 [2 d, each 3JP-C = 4.0 Hz, C(CH3)2].
31P NMR: δ = 2.00.
383.1413.
HRMS (ESI): m/z [M + H]+ calcd for C25H28O4P: 399.1726; found:
399.1726.
Acknowledgment
We thank the Department of Science and Technology (DST, New
Delhi) for financial support and for the single crystal X-ray diffrac-
tometer facility at the University of Hyderabad, and UGC (New
Delhi) for equipment under UPE and CAS programs. K.C.K. thanks
DST for a J. C. Bose fellowship. A.U. thanks UGC and R.K. thanks
CSIR (New Delhi) for fellowships.
[5-(2-Nitrobenzyl)-4-phenylfuran-2-yl]diphenylphosphine Ox-
ide (16)
Orange solid; yield: 165 mg (69%); mp 170–172 °C.
IR (KBr): 3408, 3063, 2964, 2921, 2849, 1605, 1529, 1436, 1348,
1200, 1118, 860, 762, 724, 701 cm–1.
1H NMR (400 MHz, CDCl3): δ = 7.99–7.09 (m, 20 H, HAr), 4.56 (s,
2 H, ArCH2).
Supporting Information for this article is available online at
13C NMR (100 MHz, CDCl3): δ = 153.5 (d, 3JP-C = 5.0 Hz, PCOC),
http://www.thieme-connect.com/ejournals/toc/synthesis.SnoIufproi
m
tgioSrantnugIifoop
r
itmnatr
1
148.9, 147.3 (d, JP-C = 103.0 Hz, PC), 133.3, 132.4, 131.6 (d,
3JP-C = 8.0 Hz, PC=C), 131.4, 131.0, 130.9, 128.9, 128.5 (d, 2JP-C
=
References
10.0 Hz, PC=C-C), 127.9, 127.7, 127.6, 125.1, 125.0, 124.9, 124.8,
30.8 (s, ArCH2).
(1) Selected recent articles: (a) Review: De Simone, F.; Waser,
J. Synthesis 2009, 3353. (b) Praveen, C.; Kiruthiga, P.;
Perumal, P. T. Synlett 2009, 1990. (c) Wang, A.; Jiang, H.;
Xu, Q. Synlett 2009, 929. (d) Aoyama, T.; Nagaoka, T.;
Takido, T.; Kodomari, M. Synthesis 2011, 619. (e) Review:
Bauer, E. B. Synthesis 2012, 44, 1131. (f) Jiang, H.; Zeng,
W.; Li, Y.; Wu, W.; Huang, L.; Fu, W. J. Org. Chem. 2012,
77, 5179. (g) Li, E.; Cheng, X.; Wang, C.; Shao, Y.; Li, Y.
J. Org. Chem. 2012, 77, 7744. (h) He, C.; Guo, S.; Ke, J.;
Hao, J.; Xu, H.; Chen, H.; Lei, A. J. Am. Chem. Soc. 2012,
134, 5766. (i) Account: Gao, L.; Xiong, S.; Wan, C.; Wang,
Z. Synlett 2013, 24, 1322. (j) Adib, M.; Mahdavi, M.;
Bagherzadeh, S.; Bijanzadeh, H. Synlett 2009, 2542.
31P NMR: δ = 15.8.
HRMS (ESI): m/z [M + H]+ calcd for C29H23O4NP: 480.1365;
found: 480.1365.
[5-(3-Fluorobenzyl)-4-phenylfuran-2-yl]diphenylphosphine
Oxide (17)
Pale yellow gummy solid; yield: 175 mg (78%).
IR (neat): 3051, 2920, 2843, 1747, 1616, 1588, 1484, 1440, 1254,
1205, 1117, 766, 723, 695 cm–1.
1H NMR (400 MHz, CDCl3): δ = 7.79–6.83 (m, 20 H, HAr), 4.14 (s,
2 H, ArCH2).
(k) Fujita, T.; Sakoda, K.; Ikeda, M.; Hattori, M.; Ichikawa,
© Georg Thieme Verlag Stuttgart · New York
Synthesis 2014, 46, 1197–1204

1204
A. Uravakilli et al.
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(13) (a) Crystallographic data for the structures of 3 and 18 have
been deposited with the Cambridge Crystallographic Data
Centre as supplementary publication numbers CCDC
970083–C 970084. Copies of the data can be obtained free
of charge, on application to CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK [fax: +44(1223)336033 or e-mail:
deposit@ccdc.cam.ac.uk]. (b) Sheldrick, G. M. SADABS,
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β = 97.71(3)°, V = 1978.7(7) Å3, Z = 4, μ = 0.163 mm–1,
data/restraints/parameters: 3466/2/246, R indices [I > 2σ(I)]:
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blocks, C22H23O4P, M = 382.37, monoclinic, space group
P21, a = 9.5837(9), b = 10.9418(7), c = 10.3457(9) Å,
β = 111.51(1)°, V = 1009.30(4) Å3, Z = 2, μ = 0.160 mm–1,
data/restraints/parameters: 3084/1/246, R indices [I > 2σ(I)]:
R1 = 0.0344, wR2 (all data) = 0.0836.
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Synthesis 2014, 46, 1197–1204
© Georg Thieme Verlag Stuttgart · New York