Bromodecarboxylation of (E)-3-aryl-2-(diethoxyphosphoryl)acrylic acids: A facile route to diethyl arylethynylphosphonates

Article abstract of DOI:10.1055/s-2007-966057

Bromodecarboxylation of (E)-3-aryl-2-(diethoxyphosphoryl)acrylic acids leading to diethyl (Z)-2-aryl-1-bromovinylphosphonates has been conducted for the first time. The products have been shown to be useful for the synthesis of diethyl arylethynylphosphon

Full text of DOI:10.1055/s-2007-966057

PAPER
1877
Bromodecarboxylation of (E)-3-Aryl-2-(diethoxyphosphoryl)acrylic Acids:
A Facile Route to Diethyl Arylethynylphosphonates
B
H
romodecarboxyla
e
tionof
(
E
)
-
n
3-Aryl-2-(di
r
ethoxyph
y
osphoryl)ac
k
rylic
A
cids Krawczyk,* Łukasz Albrecht
Institute of Organic Chemistry, Technical University (Politechnika), Żeromskiego 116, 90-924 Łódź, Poland
Fax +48(42)6365530; E-mail: henkrawc@p.lodz.pl
Received 26 March 2007; revised 17 April 2007
Alk-1-ynylphosphonates have found widespread applica-
tion in organic synthesis. Stereoselective partial reduc-
tion of the triple bond of dibutyl prop-1-ynylphosphonate
Abstract: Bromodecarboxylation of (E)-3-aryl-2-(diethoxyphos-
phoryl)acrylic acids leading to diethyl (Z)-2-aryl-1-bromovinyl-
phosphonates has been conducted for the first time. The products
6
have been shown to be useful for the synthesis of diethyl arylethy- to give dibutyl (Z)-prop-1-enylphosphonate constitutes a
nylphosphonates.
key step in the first racemic synthesis of the antibiotic fos-
fomycin. Hydration of alk-1-ynylphosphonates provides
7
Key words: Hunsdiecker reaction, bromodecarboxylation, alk-1-
ynylphosphonates, Oxone, acrylic acids
an effective and general approach for the preparation of 2-
oxoalkylphosphonates, versatile synthetic intermediates.8
Additionally, alk-1-ynylphosphonates have been utilized
in [2+2]-, [3+2]-, and [4+2]-cycloaddition reactions for
the synthesis of complex organophosphorus compounds.6
Alk-1-ynylphosphonates are also useful precursors for the
preparation of arylidenebisphosphonates providing a new
Decarboxylation of carboxylic acids accompanied by si-
multaneous replacement by a halogen, known in the liter-
ature as the Hunsdiecker reaction, constitutes an
important and useful method for the synthesis of haloge-
nated organic compounds containing one fewer carbon
9
access to the P–C–P backbone. Recently, the reagent sys-
1
tem Cp ZrCl /2 EtMgBr/2 AlCl was shown to convert
atom than the original acid. It is well established that sim-
2 2 3
alk-1-ynylphosphonates into cyclopropylmethylphospho-
ple alkanoic acids can be converted into the corresponding
alkyl bromides by reaction of their silver salts with ele-
1
0
nates in good isolated yields. As a consequence consid-
erable effort has been directed towards the development
of methods for their simple and effective preparation.6
mental bromine. Unfortunately, the salts of a,b-unsaturat-
ed acids were found not to be useful in this reaction.1
Recently, the Hunsdiecker reaction of cinnamic acids has Recently, we have demonstrated that Knoevenagel con-
been shown to proceed efficiently in the presence of vari- densation of (diethoxyphosphoryl)acetic acid with vari-
2
a
2b
ous reagents (NBS/iodosylbenzene,
NBS/LiOAc,
ous aromatic aldehydes gives access to a range of (E)-3-
2
c
11
NBS/LiOAc with irradiation, tetrabutylammonium tri- aryl-2-(diethoxyphosphoryl)acrylic acids 1. Moreover,
2
d
2e
fluoroacetate/N-halosuccinimides, NaX/Oxone, KBr/ we have shown that subsequent decarboxylation of the ac-
2
f
2g
Selectfluor, KBr/Na MoO ·2H O/H O , Dess–Martin ids 1 constitutes an efficient and general route to diethyl
2
4
2
2
2
2
h
2i
periodinane/TEAB, LiBr/CAN ) giving access to a (E)-2-arylvinylphosphonates. We envisioned that Huns-
range of vinyl halides.
diecker reaction of the acids 1 would provide a new ap-
proach to 1-bromoalk-1-enylphosphonates.
Halogen-substituted vinylphosphonates are masked acet-
ylenic compounds as they can be easily transformed into In this paper, we report our results on the bromodecarbox-
3
the corresponding alk-1-ynylphosphonates. Moreover, 1- ylation of acids 1 using sodium bromide in the presence of
bromoalk-1-enylphosphonates have been successfully Oxone at room temperature. Moreover, we demonstrate
utilized for the preparation of the corresponding 1-aryl- that the resulting diethyl 2-aryl-1-bromovinylphospho-
alk-1-enylphosphonates and phosphorylated dienes by nates can be easily converted into diethyl arylethy-
means of transition-metal-catalyzed arylation and alkeny- nylphosphonates, thus providing a novel approach to this
4
lation. 1-Bromoalk-1-enylphosphonates are commonly class of compounds.
prepared through a sequence of reactions involving addi-
tion of elemental bromine to alk-1-enylphosphonates and
In our initial studies, we focused on finding a suitable
method for the effective bromodecarboxylation of (E)-3-
aryl-2-(diethoxyphosphoryl)acrylic acids 1 (Scheme 1).
base-catalyzed b-elimination of the resulting 1,2-dibro-
4
,5
moalkylphosphonates. These reactions lead to the for-
mation of particular products as mixtures of E- and Z-
isomers. For this reason, methods to obtain such com-
pounds in a stereoselective manner are desirable.
(
E)-2-(Diethoxyphosphoryl)-3-(4-methoxyphenyl)acryl-
ic acid (1a) was chosen as a model substrate and various
methods for its conversion into alkenyl bromide 2a were
evaluated. The use of lithium bromide in the presence of
ammonium cerium(IV) nitrate at room temperature result-
ed in the formation of a complex reaction mixture. The re-
action of the acid 1a with potassium bromide and
hydrogen peroxide in the presence of molybdic acid pro-
ceeded rapidly, giving the desired bromide 2a in moderate
SYNTHESIS 2007, No. 12, pp 1877–1881
x
x.
x
x
.
2
0
0
7
Advanced online publication: 11.05.2007
DOI: 10.1055/s-2007-966057; Art ID: Z07307SS
Georg Thieme Verlag Stuttgart · New York
©

1
878
H. Krawczyk, Ł. Albrecht
PAPER
yield and purity. The best results in terms of yield and pu-
rity were obtained using sodium bromide in the presence
of sodium carbonate and Oxone at room temperature; un-
der these conditions the corresponding alkenyl bromide
O
(EtO)2P
Br
Ar
O
(EtO)2P
Ar
H
2
a was formed in 93% yield. Our investigation on the gen-
erality of this methodology showed that electronic effects
of the aryl substituent had a profound impact on the reac- Scheme 2 Reagents and conditions: DBU (1.5 equiv) or TBD (1.2
2
a–f
3a–f
tivity of the substrate. Reactions of 3-aryl-2-(diethoxy-
phosphoryl)acrylic acids bearing electron-withdrawing
equiv), CH Cl , r.t.
2 2
group on the aromatic ring proceeded very slowly and bromides 2a–d proceeded efficiently at room tempera-
were not chemoselective. In practice, this methodology ture.
could be efficiently applied to acrylic acids 1a–d bearing
Reactions were complete within 6–10 days giving the tar-
electron-donating groups on the aromatic ring. With the
get phosphonates 3a–d in high yields. In contrast, the re-
same reagent system, heteroaromatic-substituted acrylic
actions of the heteroaromatic-substituted bromides 2e,f
acids 1e,f also provided the respective bromodecarboxy-
were not chemoselective and led to a mixture of organo-
lation products 2e,f, but in moderate yield (Table 1).
phosphorus compounds. Much better results in terms of
reaction time were obtained using 1,5,7-triazabicyc-
lo[4.4.0]dec-5-ene (TBD) as a base. Under these condi-
tions reactions of bromides 2a–e were complete within 1–
O
O
(
EtO)2P
COOH
Ar
(EtO)2P
Br
Ar
2
days giving the target phosphonates 3a–e in comparable
H
H
yields. Unfortunately, 1,5,7-triazabicyclo[4.4.0]dec-5-
ene-promoted elimination of diethyl 2-(1-acetyl-1H-in-
dol-3-yl)-1-bromovinylphosphonate (2f) resulted in a
complex reaction mixture. In all reactions performed,
only the Z-isomer underwent b-elimination while the E-
isomer remained unreacted. The pure diethyl arylethy-
nylphosphonates 3a–e were isolated by column chroma-
tography.
1
a–f
2a–f
Scheme 1 Reagents and conditions: KBr (3 equiv), Na CO (1
equiv), Oxone (2 equiv), MeCN, H O, r.t.
2
3
2
Bromodecarboxylation of the acids 1a–f proceeded with
retention of configuration of the double bond and provid-
ed the products as the Z-isomer accompanied by a small
amount of the E-isomer (ratios Z/E are given in Table 1).
Similar results with regard to diastereoselectivity were
observed for the bromodecarboxylation of cinnamic acid
In summary, we have developed a novel and efficient
method for the preparation of diethyl 2-aryl-1-bromovi-
nylphosphonates in a highly stereoselective manner.
Moreover, we have shown that this type of compound can
be successfully used for the synthesis of diethyl arylethy-
nylphosphonates.
2
c,f,12
derivatives.
The configuration of the alkene bond in
bromides 2a–f was unambiguously assigned on the basis
of H NMR data; the value of the coupling constant
JHP = 15.5–16.3 Hz) indicate a cis relationship between
1
3
(
vicinal P and H atoms.
NMR spectra were recorded on a Bruker DPX 250 instrument at
1
13
31
2
50.13 MHz for H, 62.9 MHz for C, and 101.3 MHz for
P
With suitable substrates in hand, we turned our attention
to their effective conversion into diethyl arylethynylphos-
phonates 3a–f (Scheme 2). After much experimentation it
NMR, using TMS as internal and 85% H PO as external standard.
3
4
The multiplicity of carbons were determined by DEPT experiments.
IR spectra were measured on a Specord M80 (Zeiss) instrument. El-
was found that 1,8-diazabicyclo[5.4.0]undec-7-ene emental analyses were performed on a Perkin-Elmer PE 2400 ana-
(
DBU) promoted b-elimination of corresponding alkenyl lyzer. Melting points were determined in open capillaries and are
uncorrected.
Table 1 2-Aryl-1-bromovinylphosphonates 2a–f and Arylethynylphosphonates 3a–e Prepared
Entry Ar
Vinylphosphonate 2
Ethynylphosphonate 3
Time (min) Yield (%) Ratio Z/E
DBU-promoted reaction TBD-promoted reaction
Time (d)
Yield (%)
Time (d) Yield (%)
1
2
3
4
5
6
4-MeOC H4
2a
2b
2c
2d
2e
2f
90
90
90
90
60
60
93
84
91
67
48
43
94:6
95:5
96:4
95:5
98:2
99:1
3a
3b
3c
3d
3e
3f
7
8
72
81
77
73
–
1
1
1
1
2
–
75
80
81
72
60
–
6
4-MeC H4
6
3,4-(MeO) C H
3
10
6
2
6
3,4-(OCH O)C H
3
2
6
5-methylfuran-2-yl
–
1-acetyl-1H-indol-3-yl
–
–
Synthesis 2007, No. 12, 1877–1881 © Thieme Stuttgart · New York

PAPER
Bromodecarboxylation of (E)-3-Aryl-2-(diethoxyphosphoryl)acrylic Acids
1879
Acrylic acids 1a–f were prepared according to the literature proce-
dure.11 The synthesis and spectral data of 1f have not been previous-
ly reported.
1JCP = 206.9 Hz, PCBr), 129.15 (2 CH ), 130.02 (2 CH ), 131.02
Ar
Ar
3
2
(d, J = 17.8 Hz, C ), 140.66 (C ), 144.69 (d, J = 16.7 Hz,
CP
Ar
Ar
CP
CHAr).
3
1
P NMR (CDCl ): d = 11.65.
3
(
E)-3-(1-Acetyl-1H-indol-3-yl)-2-(diethoxyphosphoryl)acrylic
Anal. Calcd for C H BrO P: C, 46.87; H, 5.45. Found: C, 46.63;
H, 5.30.
Acid (1f)
13 18
3
Pale-yellow crystals; yield: 51%; mp 136–137 °C.
–
1
IR (film): 1716, 1448, 1372, 1330, 1252, 1056, 772 cm .
Diethyl (Z)-1-Bromo-2-(3,4-dimethoxyphenyl)vinylphospho-
nate (2c)
Yellow oil; yield: 91%.
1
H NMR (acetone-d ): d = 1.35 (t, 3JHH = 7.0 Hz, 6 H, 2
6
CH CH OP), 2.71 (s, 3 H, CH CO), 4.14–4.25 (m, 4 H, 2
3
2
3
CH CH OP), 7.33–7.45 (m, 2 H, 2 CH ), 7.75–7.79 (m, 1 H,
IR (film): 1596, 1512, 1264, 1144, 1020, 968 cm–1.
3
2
Ar
3
CH ), 7.90 (d, J = 23.9 Hz, 1 H, CHAr), 8.38–8.42 (m, 1 H,
Ar
HP
1
H NMR (CDCl ): d = 1.40 (dt, J = 7.0 Hz, 4JHP = 0.8 Hz, 6 H, 2
3
CH ), 8.51 (s, 1 H, CH ).
3
HH
Ar
Ar
CH CH OP), 3.92 (s, 3 H, CH OAr), 3.93 (s, 3 H, CH OAr), 4.11–
4
1
3
3
3
2
3
3
C NMR (MeOD): d = 15.82 (d, J = 6.1 Hz, 2 CH CH OP),
3
CP
3
2
.29 (m, 4 H, 2 CH CH OP), 6.91 (d, J = 8.3 Hz, 1 H, CHAr),
2
3 2 HH
2
2.99 (CH CO), 63.52 (d, J = 5.2 Hz, 2 CH CH OP), 115.34 (d,
JCP = 22.2 Hz, C ), 116.60 (CH ), 118.28 (CH ), 121.81 (d,
JCP = 178.9 Hz, PC), 124.48 (CH ), 125.88 (CH ), 129.84 (C ),
29.96 (CH ), 135.49 (C ), 140.19 (d, J = 7.8 Hz, CHAr),
3
4
3
CP
3
2
7
.46 (dd, JHH = 8.3 Hz, JHH = 2.0 Hz, 1 H, CH ), 7.60 (d,
JHH = 2.0 Hz, 1 H, CH ), 7.99 (d, J = 16.3 Hz, 1 H, CHAr).
3
Ar
Ar
Ar
Ar
4
3
1
Ar
HP
Ar
Ar
Ar
1
3
3
2
C NMR (CDCl ): d = 15.95 (d, J = 6.9 Hz, 2 CH CH OP),
3 CP 3 2
2
1
1
Ar
Ar
CP
2
55.61 (2 CH OAr), 62.75 (d, J = 5.2 Hz, 2 CH CH OP), 106.24
3 CP 3 2
(
(
67.73 (d, J = 11.9 Hz, COOH), 169.91 (CO).
CP
1
d, JCP = 207.9 Hz, PCBr), 110.40 (CH ), 112.19 (CH ), 124.36
CH ), 126.24 (d, J = 18.2 Hz, C ), 144.00 (d, J = 17.3 Hz,
3
1
Ar Ar
P NMR (acetone-d ): d = 15.11.
3
2
6
Ar
CP
Ar
CP
Anal. Calcd for C H NO P: C, 55.89; H, 5.52; N, 3.83. Found: C,
CHAr), 148.20 (C ), 150.54 (C ).
17
20
6
Ar
Ar
5
5.77; H, 5.43; N, 3.71.
31
P NMR (CDCl ): d = 12.04.
3
Anal. Calcd for C H BrO P: C, 44.35; H, 5.32. Found: C, 44.53;
H, 5.21.
Diethyl 2-Aryl-1-bromovinylphosphonates 2a–f; General Pro-
cedure
14 20
5
The soln of Oxone (613 mg, 1 mmol) in H O (6 mL) was added
dropwise to a mixture of acrylic acid 1 (1 mmol), NaBr (309 mg, 3
2
Diethyl (Z)-1-Bromo-2-[3,4-(methylenedioxy)phenyl]vinyl-
phosphonate (2d)
Pale-yellow oil; yield: 67%.
IR (film): 1592, 1504, 1488, 1448, 1248, 1020, 972 cm–1.
mmol), and Na CO (106 mg, 1 mmol) in MeCN (9 mL) and H O
2
3
2
(6 mL). The resulting mixture was stirred at r.t. for the indicated pe-
riod of time (Table 1). The mixture was then quenched with aq
Na S O (15 mL) and extracted with CH Cl (2 × 10 mL). The com-
2
2
3
2
2
1
H NMR (CDCl ): d = 1.39 (dt, J = 7.3 Hz, 4J = 0.3 Hz, 6 H, 2
3
3
HH
HP
bined organic layers were dried (MgSO ), filtered, and concentrated
4
CH CH OP), 4.09–4.28 (m, 4 H, 2 CH CH OP), 6.03 (s, 2 H,
CH O Ar), 6.85 (d, J = 8.2 Hz, 1 H, CH ), 7.28 (dd, J = 8.2
Hz, J = 1.8 Hz, 1 H, CH ), 7.61 (d, J = 1.8 Hz, 1 H, CHAr),
7
3
2
3
2
under reduced pressure. The crude product was purified by a col-
umn chromatography (EtOAc–hexane 2:1) affording pure 2.
3
3
2
4
2
HH
Ar
HH
4
HH
3
Ar
HH
.95 (d, J = 16.3 Hz, 1 H, CHAr).
HP
Diethyl (Z)-1-Bromo-2-(4-methoxyphenyl)vinylphosphonate
1
3
3
(
2a)
C NMR (CDCl
3
): d = 16.00 (d, JCP = 6.5 Hz, 2 CH
62.84 (d, JCP = 5.1 Hz, 2 CH CH OP), 101.40 (CH Ar), 106.88
(d, JCP = 207.6 Hz, PCBr), 108.08 (CHAr), 108.89 (CHAr), 126.15
3 2
CH OP),
2
Pale-yellow oil; yield: 93%.
3
2
O
2 2
1
–
1
IR (film): 1600, 1512, 1256, 1020, 968 cm .
3
2
(
CH ), 127.58 (d, J = 18.3 Hz, C ), 143.87 (d, J = 17.2 Hz,
Ar CP Ar CP
1
3
H NMR (CDCl ): d = 1.39 (t, J = 6.9 Hz, 6 H, 2 CH CH OP),
3
HH
3
2
CHAr), 147.40 (C ), 149.08 (C ).
Ar
Ar
3
.85 (s, 3 H, CH OPh), 4.09–4.26 (m, 4 H, 2 CH CH OP), 6.95 (d,
3
3
2
31P NMR (CDCl
3
3
3
): d = 11.48.
JHH = 8.9 Hz, 2 H, 2 CH ), 7.89 (d, J = 8.9 Hz, 2 H, 2 CHAr),
.00 (d, J = 16.3 Hz, 1 H, CHAr).
Ar
HH
3
8
Anal. Calcd for C13
H, 4.31.
H16BrO P: C, 43.00; H, 4.44. Found: C, 43.13;
5
HP
1
3
3
C NMR (CDCl ): d = 15.92 (d, J = 6.5 Hz, 2 CH CH OP),
3
CP
3
2
2
5
4.99 (CH OPh), 62.70 (d, J = 5.3 Hz, 2 CH CH OP), 106.15 (d,
JCP = 208.1 Hz, PCBr), 113.51 (2 CH ), 126.04 (d, J = 18.2 Hz,
3 CP 3 2
1
3
Diethyl (Z)-1-Bromo-2-(5-methylfuran-2-yl)vinylphosphonate
(2e)
Yellow oil; yield: 48%.
Ar
CP
2
C ), 131.68 (2 CH ), 143.84 (d, J = 17.1 Hz, CHAr), 160.83
Ar
Ar
CP
(
C ).
Ar
–
1
3
1
IR (film): 1616, 1584, 1516, 1252, 1024, 972 cm .
P NMR (CDCl ): d = 11.74.
3
1
H NMR (CDCl ): d = 1.37 (dt, J = 7.0 Hz, 4JHP = 0.5 Hz, 6 H, 2
3
3
HH
Anal. Calcd for C H BrO P: C, 44.72; H, 5.20. Found: C, 44.63;
13
18
4
CH CH OP), 2.35 (s, 3 H, CH Ar), 4.06–4.23 (m, 4 H, 2
CH CH OP), 6.17 (d, J = 3.3 Hz, 1 H, CH ), 7.24 (d, J = 3.3
Hz, 1 H, CH ), 7.90 (d, J = 15.8 Hz, 1 H, CHAr).
3
2
3
H, 5.30.
3
3
3
2
HH
3
Ar
HH
Ar
HP
Diethyl (Z)-1-Bromo-2-(4-methylphenyl)vinylphosphonate (2b)
Pale-yellow oil; yield: 84%.
13C NMR (CDCl
): d = 13.70 (CH
Ar), 16.08 (d, 3JCP = 6.6 Hz, 2
3
3
2
–
1
CH
3
CH
2
OP), 62.86 (d, JCP = 5.2 Hz, 2 CH
3
CH
2
OP), 103.54 (d,
IR (film): 1604, 1440, 1252, 1020, 968 cm .
1
JCP = 211.2 Hz, PCBr), 108.72 (CH ), 117.56 (CH ), 132.87 (d,
Ar
3
Ar
1
H NMR (CDCl ): d = 1.39 (dt, J = 7.0 Hz, 4JHP = 0.8 Hz, 6 H, 2
3
2
3
HH
JCP = 18.9 Hz, CHAr), 148.28 (d, J = 22.5 Hz, C ), 155.10
CP
Ar
CH CH OP), 2.38 (s, 3 H, CH Ph), 4.11–4.26 (m, 4 H, 2
3
2
3
(C ).
Ar
3
CH CH OP), 7.23 (d, JHH = 8.0 Hz, 2 H, 2 CH ), 7.76 (d,
3
2
Ar
31P NMR (CDCl
3
1
3
3
): d = 12.06.
JHH = 8.0 Hz, 2 H, 2 CH ), 8.02 (d, J = 16.3 Hz, 1 H, CHAr).
Ar
HP
3
3
Anal. Calcd for C11
H, 4.81.
H16BrO P: C, 40.89; H, 4.99. Found: C, 40.73;
4
C NMR (CDCl ): d = 16.25 (d, J = 6.4 Hz, 2 CH CH OP),
1.51 (CH Ph), 63.11 (d, J = 5.2 Hz, 2 CH CH OP), 108.48 (d,
3 CP 3 2
3
CP
3
2
2
2
Synthesis 2007, No. 12, 1877–1881 © Thieme Stuttgart · New York

1
880
H. Krawczyk, Ł. Albrecht
PAPER
Diethyl (Z)-2-(1-Acetyl-1H-indol-3-yl)-1-bromovinyl-
phosphonate (2f)
Anal. Calcd for C H O P: C, 61.90; H, 6.79. Found: C, 61.77; H,
6.65.
1
3
17
3
Yellow oil; yield: 43%.
–
1
Diethyl 3,4-Dimethoxyphenylethynylphosphonate (3c)
White crystals; yield: 81%; mp68–70 °C.
IR (film): 2176, 1600, 1512, 1444, 1252, 1024, 960 cm–1.
IR (film): 1716, 1448, 1376, 1332, 1252, 1212, 1056, 972 cm .
1
H NMR (CDCl ): d = 1.41 (dt, J = 7.0 Hz, 4JHP = 0.5 Hz, 6 H, 2
CH CH OP), 2.73 (s, 3 H, CH C(O)N), 4.11–4.29 (m, 4 H, 2
CH CH OP), 7.34–7.47 (m, 2 H, 2 CH ), 7.75 (dd, J = 6.5 Hz,
JHH = 1.2 Hz, 1 H, CH ), 8.30 (d, J = 15.5 Hz, 1 H, CHAr), 8.46
3
3
HH
3
2
3
3
1
3
H NMR (CDCl ): d = 1.41 (t, J = 7.0 Hz, 6 H, 2 CH CH OP),
3
2
Ar
HH
3
HH
3
2
4
3
3.89 (s, 3 H, CH OAr), 3.92 (s, 3 H, CH OAr), 4.17–4.29 (m, 4 H,
Ar
HP
3
3
3
4
3
(
dd, J = 7.2 Hz, J = 1.2 Hz, 1 H, CH ), 8.65 (s, 1 H, CH ).
2 CH CH OP), 6.84 (d, JHH = 8.2 Hz, 1 H, CH ), 7.04 (d,
3 2 Ar
HH
HH
Ar
Ar
4
3
4
1
3
3
JHH = 2.0 Hz, 1 H, CHAr), 7.20 (dd, JHH = 8.2 Hz, JHH = 2.0 Hz,
C NMR (CDCl ): d = 16.13 (d, J = 6.5 Hz, 2 CH CH OP),
3
CP
3
2
2
1 H, CHAr).
2
3.80 [CH C(O)N], 63.05 (d, J = 5.2 Hz, 2 CH CH OP), 110.02
3 CP 3 2
1
3
13
3
(
(
(
(
3
d, J = 208.8 Hz, PCBr), 116.00 (d, J = 18.9 Hz, C ), 116.42
CH ), 118.24 (CH ), 124.14 (CH ), 126.02 (CH ), 126.29
CH ), 129.31 (C ), 134.53 (d, J = 18.6 Hz, CHAr), 134.68
C NMR (CDCl ): d = 15.83 (d, J = 7.0 Hz, 2 CH CH OP),
3 CP 3 2
2
CP
CP
Ar
55.67 (2 CH OAr), 62.85 (d, J = 5.5 Hz, 2 CH CH OP), 76.66 (d,
3 CP 3 2
Ar
Ar
Ar
Ar
3
1
2
JCP = 301.7 Hz, PC), 99.57 (d, JCP = 53.7 Hz, CAr), 110.82
Ar
Ar
CP
3
C ), 168.51 [C(O)N].
1
(CH ), 110.92 (d, JCP = 6.0 Hz, C ), 114.49 (CH ), 126.43
Ar
Ar
Ar
Ar
(CHAr), 148.46 (CAr), 151.22 (CAr).
P NMR (CDCl ): d = 10.76.
3
3
1
P NMR (CDCl ): d = –4.77.
3
Anal. Calcd for C H BrNO P: C, 48.02; H, 4.79; N, 3.50. Found:
1
6
19
4
C, 48.13; H, 4.88; N, 3.59.
Anal. Calcd for C H O P: C, 56.37; H, 6.42. Found: C, 56.49; H,
14 19 5
6
.55.
Diethyl Arylethynylphosphonates 3a–e; General Procedure
A soln of a corresponding 1-bromovinylphosphonate 2 (1 mmol)
and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (167 mg, 1.2 mmol) in
CH Cl (10 mL) was stirred at r.t. for the appropriate period of time
Diethyl 3,4-(Methylenedioxy)phenylethynylphosphonate (3d)3d
Pale-yellow oil; yield: 72%.
IR (film): 2176, 1440, 1252, 1168, 1032, 968 cm–1.
2
2
(
Table 1). The reaction progress was occasionally monitored with
P NMR. After the bromide 2 was completely reacted the mixture
1
3
3
1
H NMR (CDCl ): d = 1.40 (t, J = 7.0 Hz, 6 H, 2 CH CH OP),
3
HH
3
2
4
.16–4.28 (m, 4 H, 2 CH CH OP), 6.02 (s, 2 H, CH O Ar), 6.79 (d,
was successively washed with 1 M HCl (10 mL) and H O (10 mL)
3 2 2 2
2
3
4
JHH = 8.2 Hz, 1 H, CH ), 6.97 (d, J = 1.5 Hz, 1 H, CH ), 7.12
and dried (MgSO ). Evaporation of the solvent under reduced pres-
Ar
HH
Ar
4
4
(
dd, 3J = 8.2 Hz, J = 1.5 Hz, 1 H, CHAr).
sure afforded the crude product, which was purified by column
chromatography (EtOAc–hexane 2:1) to give pure 3.
HH HH
13
3
C NMR (CDCl ): d = 15.72 (d, J = 7.0 Hz, 2 CH CH OP),
3
CP
3
2
2
1
6
2.77 (d, J = 5.5 Hz, 2 CH CH OP), 76.44 (d, J = 301.0 Hz,
CP 3 2 CP
Diethyl 4-Methoxyphenylethynylphosphonate (3a)3d
Pale-yellow oil; yield: 75%.
2
PC), 99.02 (d, J = 53.2 Hz, CAr), 101.48 (CH O Ar), 108.32
CP
2
2
3
(
CH ), 111.56 (CH ), 111.95 (d, JCP = 5.8 Hz, C ), 127.80
Ar Ar Ar
–
1
(CH ), 147.24 (C ), 149.64 (C ).
IR (film): 2184, 1604, 1512, 1256, 1028 cm .
Ar Ar Ar
3
1
1
3
P NMR (CDCl ): d = –5.04.
3
H NMR (CDCl ): d = 1.40 (t, J = 7.0 Hz, 6 H, 2 CH CH OP),
3
HH
3
2
3
2
2
.84 (s, 3 H, CH OPh), 4.17–4.30 (m, 4 H, 2 CH CH OP), 6.88 (d,
3
3
2
Anal. Calcd for C H O P: C, 55.32; H, 5.36. Found: C, 55.23; H,
13 15 5
5.46.
3
3
H, J = 8.8 Hz, 2 H, 2 CH ), 7.51 (d, 2 H, J = 8.8 Hz, 2 H,
HH
Ar
HH
CH ).
Ar
1
3
3
Diethyl 5-Methylfuran-2-ylethynylphosphonate (3e)
Pale-yellow oil; yield: 60%.
IR (film): 2176, 1592, 1528, 1268, 1024 cm–1.
C NMR (CDCl ): d = 15.86 (d, J = 6.9 Hz, 2 CH CH OP),
3
CP
3
2
2
5
5.14 (CH OPh), 62.85 (d, J = 5.5 Hz, 2 CH CH OP), 76.86 (d,
JCP = 302.0 Hz, PC), 99.60 (d, J = 53.8 Hz, CAr), 110.95 (d,
JCP = 5.7 Hz, C ), 114.02 (2 CH ), 134.12 (2 CH ), 161.23 (C ).
1
3 CP 3 2
1
2
CP
3
3
Ar
Ar
Ar
Ar
1
H NMR (CDCl ): d = 1.40 (dt, J = 7.1 Hz, 4J = 0.7 Hz, 6 H, 2
3
3
HH
HP
P NMR (CDCl ): d = –4.74.
3
CH CH OP), 2.33 (s, 3 H, CH Ar), 4.15–4.28 (m, 4 H, 2
CH CH OP), 6.05 (d, J = 3.4 Hz, 1 H, CH ), 6.80 (d, J = 3.4
3
2
3
3
3
Anal. Calcd for C H O P: C, 58.21; H, 6.39. Found: C, 58.09; H,
6
3
2
HH
Ar
HH
1
3
17
4
Hz, 1 H, CHAr).
.30.
1
3
3
C NMR (CDCl ): d = 13.66 (CH Ar), 15.83 (d, J = 7.1 Hz, 2
3
3
CP
Diethyl 4-Methylphenylethynylphosphonate (3b)3d
Pale-yellow oil; yield: 80%.
2
CH CH OP), 63.11 (d, J = 5.5 Hz, 2 CH CH OP), 83.07 (d,
3
2
CP
3
2
1
2
JCP = 297.0 Hz, PC), 89.16 (d, JCP = 53.9 Hz, CAr), 107.47
3
–
1
(CH ), 121.45 (CH ), 132.46 (d, J = 6.6 Hz, C ), 156.21 (C ).
IR (film): 2184, 1608, 1512, 1264, 1024, 976 cm .
1
Ar Ar CP Ar Ar
3
1
3
P NMR (CDCl ): d = –5.90.
3
H NMR (CDCl ): d = 1.40 (t, J = 8.0 Hz, 6 H, 2 CH CH OP),
.38 (s, 3 H, CH Ph), 4.17–4.29 (m, 4 H, 2 CH CH OP), 7.18 (d,
JHH = 8.0 Hz, 2 H, 2 CH ), 7.46 (d, J = 8.0 Hz, 2 H, 2 CHAr).
3
3
HH
3
2
2
3
3
2
Anal. Calcd for C H O P: C, 54.55; H, 6.24. Found: C, 54.40; H,
11 15 4
6.33.
3
3
Ar
HH
1
3
C NMR (CDCl ): d = 15.85 (d, J = 7.0 Hz, 2 CH CH OP),
3
CP
3
2
2
2
1.40 (CH Ph), 62.91 (d, J = 5.6 Hz, 2 CH CH OP), 77.46 (d,
JCP = 300.8 Hz, PC), 99.38 (d, J = 53.5 Hz, CAr), 116.10 (d,
JCP = 5.7 Hz, C ), 129.09 (2 CH ), 132.27 (2 CH ), 141.10 (C ).
1
3 CP 3 2
1
2
References
CP
3
3
Ar
Ar
Ar
Ar
(1) (a) Hunsdiecker, H.; Hunsdiecker, C. Ber. Dtsch. Chem.
Ges. B. 1942, 75, 291. (b) Wilson, C. V. Org. React. 1957,
P NMR (CDCl ): d = –5.02.
3
9
5
, 332. (c) Johnson, R. G.; Ingham, R. K. Chem. Rev. 1956,
6, 219.
Synthesis 2007, No. 12, 1877–1881 © Thieme Stuttgart · New York

PAPER
(
Bromodecarboxylation of (E)-3-Aryl-2-(diethoxyphosphoryl)acrylic Acids
(6) (a) Savignac, P.; Iorga, B. In Modern Phosphonate
1881
2) (a) Graven, A.; Jørgensen, K. A.; Dahl, S.; Stanczak, A. J.
Org. Chem. 1994, 59, 3543. (b) Chowdhury, S.; Roy, S. J.
Chemistry; CRC Press: Boca Raton, 2003, Chap. 1.
(b) Iorga, B.; Eymery, F.; Carmichael, D.; Savignac, P. Eur.
J. Org. Chem. 2000, 3103.
Org. Chem. 1997, 62, 199. (c) Kuang, C.; Yang, Q.;
Senboku, H.; Tokuda, M. Synthesis 2005, 1319. (d) Naskar,
D.; Roy, S. Tetrahedron 2000, 56, 1369. (e) You, H.-W.;
Lee, K.-J. Synlett 2001, 105. (f) Ye, C.; Shreeve, J. M. J.
Org. Chem. 2004, 69, 8561. (g) Sinha, J.; Layek, S.;
Mandal, G. C.; Bhattacharjee, M. Chem. Commun. 2001,
(7) Christensen, B. G.; Leanza, W. J.; Beattie, T. R.; Patchett, A.
A.; Arison, B. H.; Ormond, R. E.; Kuehl, F. A. Jr.; Albers-
Schonberg, G.; Jardetzky, O. Science 1969, 166, 123.
(8) (a) Sturtz, G.; Charrier, C.; Normant, H. Bull. Soc. Chim. Fr.
1966, 1707. (b) Corey, E. J.; Virgil, S. C. J. Am. Chem. Soc.
1990, 112, 6429. (c) Guile, S. D.; Saxton, J. E.; Thornton-
Pett, M. J. Chem. Soc., Perkin Trans. 1 1992, 1763.
(d) Peiffer, G.; Courbis, P. Can. J. Chem. 1974, 52, 2894.
(9) Lecerclé, D.; Sawicki, M.; Taran, F. Org. Lett. 2006, 8,
4283.
1916. (h) Telvekar, V. N.; Arote, N. D.; Herlekar, O. P.
Synlett 2005, 2495. (i) Roy, S. C.; Guin, C.; Maiti, G.
Tetrahedron Lett. 2001, 42, 9253.
(
3) (a) Murayama, M.; Matsumura, S.; Etsure, Y.; Ozaki, M. JP
7
,510,571, 1975; Chem. Abstr. 1975, 83, 164368. (b) Hall,
R. G.; Trippett, S. Tetrahedron Lett. 1982, 23, 2603.
c) Jungheim, L. N.; Sigmund, S. K. J. Org. Chem. 1987, 52,
(
(10) Al Aziz Quntar, A.; Srebnik, M. J. Org. Chem. 2006, 71,
730.
4007. (d) Dizière, R.; Savignac, P. Tetrahedron Lett. 1996,
3
7, 1783.
(11) Krawczyk, H.; Albrecht, Ł. Synthesis 2005, 2887.
(12) Kuang, C.; Zang, Q.; Senboku, H.; Tokuda, M. Tetrahedron
2005, 61, 637.
(
(
4) (a) Kobayashi, Y.; William, A. D. Org. Lett. 2002, 4, 4241.
b) Kobayashi, Y.; William, A. D. Adv. Synth. Catal. 2004,
46, 1749.
(
3
5) (a) Stevens, C. V.; Vanderhoydonck, B. In Comprehensive
Organic Functional Group Transformations II, Vol. 4;
Katritzky, A. R.; Taylor, R. J. K., Eds.; Elsevier: Oxford,
2
005, Chap. 18. (b) Laureyn, I.; Stevens, C. V.; Kowalczyk,
R. Synlett 2004, 1823. (c) Sainz-Diaz, C. I.; Gálvez-Ruano,
E.; Hernández-Laguna, A.; Bellanato, J. J. Org. Chem. 1996,
6
3
0, 74. (d) Rengaraju, S.; Berlin, K. D. J. Org. Chem. 1972,
7, 3304.
Synthesis 2007, No. 12, 1877–1881 © Thieme Stuttgart · New York