Stereospecific synthesis of phosphono-(1Z,3E)-dienyl compounds from β-phenyltelluro-vinylphosphonates and -vinylphosphine oxides

Article abstract of DOI:10.1016/S0022-328X(03)00671-5

Phosphono-1,3-dienyl compounds 2 can be prepared by palladium cross-coupling reaction of β-phenyltelluro-vinylphosphonates or -vinylphosphine oxides with alkenes in the presence of a catalytic amount of PdCl₂ and AcOAg as reoxidant agent at room temperature. The coupling reaction is stereospecific and the compounds 2 were obtained in good yields with total retention of configuration.

Full text of DOI:10.1016/S0022-328X(03)00671-5

Journal of Organometallic Chemistry 682 (2003) 35Á40
/
www.elsevier.com/locate/jorganchem
Stereospecific synthesis of phosphono-(1Z,3E)-dienyl compounds
from b-phenyltelluro-vinylphosphonates and -vinylphosphine oxides
Antonio L. Braga *, Cristiano R.B. Rhoden, Gilson Zeni, Claudio C. Silveira,
Leandro H. Andrade
Departamento de Qu´ımica, Universidade Federal de Santa Maria, Santa Maria, RS 97105-900, Brazil
Received 3 May 2003; received in revised form 10 July 2003; accepted 11 July 2003
Abstract
Phosphono-1,3-dienyl compounds 2 can be prepared by palladium cross-coupling reaction of b-phenyltelluro-vinylphosphonates
or -vinylphosphine oxides with alkenes in the presence of a catalytic amount of PdCl2 and AcOAg as reoxidant agent at room
temperature. The coupling reaction is stereospecific and the compounds 2 were obtained in good yields with total retention of
configuration.
# 2003 Elsevier B.V. All rights reserved.
Keywords: Phosphine oxide; Phosphonates; Tellurium; Dienes; Palladium; Cross-coupling
1. Introduction
recently been investigating the hydrochalcogenation of
1-alkynylphosphonates [9] and hydrotelluration of 1-
alkynylphosphine oxides [7a]. We have found that the b-
n-butyltelluro-vinylphosphonates or -vinylphosphine
oxides, obtained from 1-alkynylphosphono compounds,
can be transformed into their correspondent enynepho-
sphonates and enynephosphine oxides via a Palladium-
catalyzed cross-coupling reaction (Scheme 1).
In connection with our continued studies in cross-
coupling reactions catalyzed by palladium [7], now we
wish to report that b-phenyltelluro vinylphosphine
oxides and -vinylphosphonates 1 readily react with
alkenes in a Heck-type reaction providing the phospho-
no-(1Z,3E)-dienyl compounds 2 with total regio and
stereocontrol (Scheme 2).
Unsaturated phosphono compounds containing elec-
tron-withdrawing substituents as well as other heteroa-
tom-functionalized moieties have been widely utilized in
organic synthesis during the last two decades, and have
furnished many synthetic possibilities [1].
Stereodefined conjugated dienes and enynes represent
a class of important synthetic intermediates and are a
part of a variety of natural products of biological
interest [2,3], such as sorbic acid and abscisic acid.
These systems have also been found in several classes of
pheromones like those from Thysanoplusia intermixta
[4] and Thaumetopoea processionea [5]. Dienylpho-
sphorus compounds containing a (Z)-olefinic moiety
are synthetically useful due to their potential to act as
dienophiles or as Michael acceptors, an could also be
regarded as an analog of abscisic acid. On the other
hand, vinylic tellurides have been used as vinyl carboca-
tion equivalent in Heck [6] and Sonogashira type [7]
cross-coupling reactions.
2. Results and discussion
The required starting b-phenyltelluro vinylphosphono
compounds 1 were prepared by addition of alkynylpho-
sphine oxides or alkynylphosphonates to a solution of
sodium phenyl tellurolate, prepared by reduction of
diphenyl ditelluride with sodium borohydride in ethanol
at room temperature [7a,9].
Thus, as part of our continuing interest in vinylic
tellurides and vinylphosphono compounds [8], we have
* Corresponding author. Tel.: ꢀ
E-mail address: albraga@quimica.ufsm.br (A.L. Braga).
/
55-2-20-8761; fax: ꢀ55-2-20-8031.
/
0022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00671-5

36
A.L. Braga et al. / Journal of Organometallic Chemistry 682 (2003) 35Á40
/
Scheme 1.
Our initial goal in the study of this reaction was to
Table 1
Reaction of b-phenyltelluro vinylphosphine oxide 1d with styrene
investigate the effects of a variety of reaction conditions
including base, solvent, reoxidant, and palladium (II)
salt. b-organotelluro vinylphosphine oxide 1d and
styrene were chosen as standards to optimize the
reaction. The results are summarized in Table 1.
Initially, treatment of compound 1d with styrene
using a stoichiometric amount of PdCl2 in methanol at
room temperature for 24 h afforded the phosphono-1,3-
dienyl compound 2g in 99% yield (Entry 1, Table 1). In
the search for a catalytic process, the amount of
palladium chloride was reduced to 0.15 equivalents,
but the desired compound 2g was obtained in only 13%
yield (Entry 2, Table 1). According to the reported
mechanism in the literature for this reaction, the use of a
reoxidant for palladium (II) is necessary [6]. The choice
of the better reoxidant for this reaction started with
silver acetate, which furnished the desired compound 2g
in a very good yield (Entry 3, Table 1). CuCl2 and FeCl3
were also tested, but they were not efficient in reoxidiz-
ing palladium to the active specie (see Entries 8 and 9).
When potassium phosphate was used as a base in place
of triethylamine, we obtained product 2g in lower yield
(75%, Entry 6, Table 1). Acetonitrile was tested as
Entry PdII salt (equiva-
lents)
Base
Oxidant Product 2g Yield a
(%)
1
PdCl2 (1.00)
PdCl2 (0.15)
PdCl2 (0.15)
PdCl2 (0.10)
PdCl2 (0.15) b
PdCl2 (0.15)
PdCl2 (0.10)
PdCl2 (0.15)
PdCl2 (0.15)
Pd(OAc)2 (0.15)
Et3N
Et3N
Á
Á/
/
99
13
2
3
Et3N AcOAg 93
Et3N AcOAg 60
Et3N AcOAg 45
K3PO4 AcOAg 75
K3PO4 AcOAg 50
4
5
6
7
8
Et3N FeCl3
Et3N CuCl2
Et3N AcOAg 63
13
9
10
Á/
Carried out with compound 1d (0.5 mmol), oxidant (2 mmol),
styrene (2 mmol), methanol (5 ml) and Et3N (2 mmol) at 25 8C for 24
h.
a
Isolated yield after purification by column chromatography on
silica gel (EtOAc:Hexane/3:7).
b
Reaction solvent: acetonitrile.
Scheme 2.

A.L. Braga et al. / Journal of Organometallic Chemistry 682 (2003) 35Á
/40
37
Table 2
Synthesis of phosphono-1,3-dienyl compounds 2 according to conditions described in Scheme 2
solvent yielding compound 2g in 45%. From the analysis
of the results summarized in Table 1, the PdCl2ÁEt3NÁ
these results, we applied this methodology to prepare
several phosphono-1,3-dienyl compounds 2 (Table 2). In
all cases studied, we observed the formation of a small
amount of trans-stilbene or trans-styryl methyl ketone
due to the coupling reaction of phenyl moiety of 1 with
the alkene. The phosphono-(1Z,3E)-dienyl compounds
2 were isolated as oils or solids after column chromato-
graphy on silica gel, using as eluent a mixture of hexane
and ethyl acetate. The regio- and stereochemistry
/
/
AcOAg system has revealed to be the best amongst
those examined for the cross-coupling reaction. Then,
the optimum conditions for this reaction was the use of
PdCl2 (15 mol.%), AcOAg (2 mmol), Et3N (2 mmol),
methanol (5 ml), b-phenyltelluro vinylphosphono com-
pounds 1 (0.5 mmol) and the appropriate alkene (2
mmol) at room temperature for 24 h. On the base of

38
A.L. Braga et al. / Journal of Organometallic Chemistry 682 (2003) 35Á40
/
1
2
3
(1Z,3E) of products 2 were readily determined by H-
NMR spectral analysis. For example, the coupling
constants for vinylic hydrogens of the new double
115.29, 61.27 (d, JPÃC
ꢂ
/
5 Hz), 41.67 (d, JPÃC
ꢂ23
/
3
Hz), 31.56, 21.16, 15.94 (d, JPÃC
m/z (relative intensity) 426(Mꢀ
ꢂ
/
6.2 Hz), 13.05; MS
2, 25), 347(15), 219(76),
/
bond formed are in agreement with typical values (15Á
/
163(80), 81(100); Anal. Calc. for C16H25O3PTe: C,
45.33; H, 5.94. Found: C44.91; H, 5.80%. IR (film,
cmꢃ1): 3064, 2956, 2870, 1559, 1433, 1391, 1292, 1231,
1163, 1027, 965, 848, 797, 737, 696.
17 Hz), for a trans relationship between them. There is
no evidence of the presence of the (Z) isomer, comprov-
ing the highly stereoselective character of the coupling
reaction. Moreover, the reaction proceeds with retention
of the stereochemistry of the original double bond of the
starting telluride 1.
3.3. Preparation of phosphono-1,3-dienyl compounds 2aÁ
/
h: general procedure
In summary, we have developed a simple and
convenient catalytic method for the stereospecific pre-
paration of phosphono-(1Z,3E)-dienyl compounds 2
from b-phenyltelluro vinylphosphono compounds 1.
The reaction proceeds cleanly under mild conditions
and substituents such as phosphine oxides, ketone and
phosphonates are tolerated quite well. Further studies of
the dienylphosphono compounds as dienophile in
To a solution of PdCl2 (15 mol.%, 13.3 mg, 0.075
mmol), AcOAg (334 mg, 2 mmol), Et3N (202 mg, 2
mmol) in MeOH (5 ml) at 25 8C, b-phenyltelluro
vinylphosphono 1 (0.5 mmol) and the appropriate
alkene (2 mmol) were added. The reaction mixture was
stirred for 24 h. Then, the mixture was filtered through a
pad of celite. The filtrate was poured into a saturated
aqueous solution of NH4Cl (5 ml) and the aqueous layer
DielsÁAlder reactions are in progress in our group.
/
was extracted with ethyl acetate (3ꢁ20 ml). The organic
/
layer was dried over MgSO4, filtered and the solvent was
removed under vacuum. The residue was purified by
column chromatography on silica gel using as eluent a
mixture of hexane and ethyl acetate (7:3) to afford the
products 2.
3. Experimental
3.1. General
1H- and 13C-NMR spectra of CDCl3 solutions were
recorded on a 200 MHz (Bruker DPX 200). Chemical
shifts are expressed as parts per million with respect to
tetramethylsilane as an internal standard. High-resolu-
tion mass spectra were obtained at 70 eV with a Bruker
Bioapex. Reactions were conducted under argon atmo-
3.3.1. Compound 2a: oil
1H-NMR (200 MHz, CDCl3): dꢂ
/
8.04 (d, 1H, Jꢂ
7.13 (m, 10H); 6.47 (d, 1H, Jꢂ16.1 Hz);
5.49 (d, 1H, JPÃH 15.8 Hz); 4.16Á3.98 (m, 4H); 1.17 (t,
6H, Jꢂ
7.8 Hz). 13C-NMR (50 MHz, CDCl3) dꢂ
158.66 (d, JPÃC 6.5 Hz); 140.24 (d, JPÃC 22.1 Hz);
138.57; 136.08; 132.33; 128.91; 128.44; 128.34; 127.65;
126.89; 125.99 (d, JPÃC 8.2 Hz); 115.27 (d, JPÃC
182.8 Hz); 61.43 (d, JPÃC 5.5 Hz); 16.13 (d, JPÃC
14.5 Hz). HRMS Calc. for C20H23O3P: [MꢀNa]
365.1282; [Mꢀ
Na] Found: 365.1268. IR (Film; cmꢃ1):
/
16.1 Hz); 7.36Á
/
/
ꢂ
/
/
/
/
sphere. Merck silica gel (230Á
flash chromatography.
/400 mesh) was used for
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
3.2. Preparation of b-organotelluro vinylphosphono
compounds 1aÁd [7a,9]
ꢂ
/
ꢂ
/
/
/
/
To a solution of RTeNa [generated in situ from
RTeTeR (1 mmol) and NaBH4 (2.2 mmol)] in absolute
ethanol (10 ml) the 1-alkynylphosphono compound was
added dropwise at room temperature. The reaction
mixture was stirred for 5 h. Then the mixture was
poured into a saturated aqueous solution of NH4Cl (10
ml) and the aqueous layer was extracted with ethyl
3065, 3018, 2984, 2927, 2908, 2188, 1617, 1574, 1555,
1493, 1445, 1388, 1245, 1154, 1016, 954, 826, 745, 692.
3.3.2. Compound 2b: oil
1H-NMR (200 MHz, CDCl3): dꢂ
/
8.41 (d, 1H, Jꢂ
7.17 (m, 5H); 5.97 (d, 1H, Jꢂ 16.3 Hz);
5.83 (d, 1H, JPÃH 14.5 Hz); 4.17Á4.02 (m, 4H); 2.3 (s,
3H); 1.29 (t, 6H, 7.1 Hz). 13C-NMR (50 MHz, CDCl3)
dꢂ198.90; 156.18 (d, JPÃC 5.7 Hz); 139.68 (d, JPÃC
8.3 Hz); 138.56 (d, JPÃC 21.3 Hz); 135.68; 128.84;
128.33; 128.04; 122.54 (d, JPÃC 181.5 Hz); 61.83 (d,
JPÃC 5.6 Hz); 26.55; 16.18 (d, JPÃC 6.2 Hz); HRMS
Na]
/
16.3 Hz); 7.31Á
/
/
ꢂ
/
/
acetate (2ꢁ25 ml). The organic layer was dried over
/
MgSO4 and filtered, and the solvent was removed under
vacuum. The residue was purified by flash chromato-
graphy on silica gel using as eluent a mixture of ethyl
acetate and hexane (3:7) to afford the products 1. 1b:
/
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
1H-NMR (200 MHz, CDCl3): d 7.92 (d, Jꢂ
/
7.6 Hz,
16.4 Hz, 1H),
Calc. for C16H21O4P [Mꢀ
/
Na] 331.1075; [Mꢀ
/
2
2H), 7.42Á
/
7.21 (m, 3H), 6.27 (d, JPÃH
ꢂ
/
Found: 331.1066. IR (Film; cmꢃ1): 2951, 2918, 2856,
1669, 1450, 1245, 1054, 1021, 964.
3
4.11 (dq, JPÃH
7.8 Hz, 2H), 1.40Á
1.00 (sext, Jꢂ7.4 Hz, 2H), 0.66 (t, Jꢂ
NMR (50 MHz, CDCl3): d 154.75 (d, JPÃC
ꢂ
/
7.5 Hz, Jꢂ
1.23 (m, 2H), 1.35 (t, Jꢂ
7 Hz, 3H); 13C-
/
7.2 Hz, 4H), 2.21 (t, Jꢂ
/
/
/
7.2 Hz, 6H),
/
/
3.3.3. Compound 2c: oil
1H-NMR (200 MHz, CDCl3): dꢂ
2
ꢂ
/
6.3 Hz),
/
7.84 (d, 1H, Jꢂ
/
1
141.43, 128.58, 128.27, 115.33 (d, JPÃC
ꢂ
/
192 Hz),
16.2 Hz); 7.39 (d, 2H, Jꢂ
/
7.1 Hz); 7.24Á7.10 (m, 3 H);
/

A.L. Braga et al. / Journal of Organometallic Chemistry 682 (2003) 35Á
/40
39
6.73 (d, 1H, Jꢂ
4.05Á3.89 (m, 4H); 2.35 (t, 2H, Jꢂ
(m, 4H); 1.20 (t, 6H, Jꢂ7.0 Hz); 0.82 (t, 3H, Jꢂ
Hz). 13C-NMR (50 MHz, CDCl3) dꢂ
157.76 (d, JPÃC
4.9 Hz); 136.06; 133.22; 128.15; 128.01; 126.75; 125.38
(d, JPÃC 9.1 Hz); 113.45 (d, JPÃC 184.3 Hz); 60.83 (d,
JPÃC 5.3 Hz); 33.86 (d, JPÃC 20.8 Hz); 30.51; 22.01;
15.86 (d, JPÃC 6.3 Hz), 13.38. HRMS Calc. for
C18H27O3P: [Mꢀ Na] Found:
/
16.2 Hz); 5.38 (d, 1H, JPÃH
ꢂ
/
15.9 Hz);
1.15
7.1
(d, 1H, Jꢂ
(t, 2H, Jꢂ7.0 Hz); 1.61 (m, 2H, Jꢂ
2H, Jꢂ7.3 Hz); 0.95 (t, 3H, Jꢂ
7.1 Hz). 13C-NMR (50
MHz, CDCl3) dꢂ159.14; 135.90; 135.03 (d, JPÃC
139.3 Hz); 133.82; 131.35 (d, JPÃC 2.6 Hz); 130.93 (d,
JPÃC 9.7 Hz); 128.49 (d, JPÃC 12 Hz); 128.46; 128.37;
127.29; 126.12 (d, JPÃC 9.5 Hz); 118.46 (d, JPÃC
101.2 Hz); 34.79 (d, JPÃC 15.1 Hz); 31.21; 22.63;
13.87. HRMS Calc. for C26H27OP: [MꢀNa] 409.1697;
[Mꢀ
Na] Found: 409.1687. IR (KBr, cmꢃ1): 3048, 2954,
/
16.2 Hz); 5.97 (d, 1H, JPÃH
ꢂ
/
23.1 Hz); 2.56
/
/
7.1 Hz); 1.52Á
/
/
/7.1 Hz); 1.42 (m,
/
/
/
/
/
ꢂ
/
/
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
/
Na] 345.1595; [Mꢀ
/
/
345.1585. IR (Film, cmꢃ1): 3056, 3022, 2979, 2956,
2922, 2875, 1631, 1583, 1450, 1388, 1240, 1159, 1021,
950, 749, 688.
/
2924, 2889, 2859, 1634, 1555, 1440, 1171, 1116, 962, 887,
823, 748.
3.3.4. Compound 2d: oil
3.3.8. Compound 2h: m.p. 80Á
1H-NMR (200 MHz, CDCl3): dꢂ
16.5 Hz); 7.64 (m, 4H); 7.32 (m, 6H); 6.2 (d, 1H, JPÃH
22.9 Hz); 6.17 (d, 1H, Jꢂ16.5 Hz); 2.37 (t, 2H, 7.0 Hz);
2.18 (s, 3H); 1.35 (m, 4H); 0.83 (t, 3H, 7.1 Hz). 13C-
NMR (50 MHz, CDCl3) dꢂ199.83; 157.02; 140.23 (d,
JPÃC 8.9 Hz); 133.68 (d, JPÃC 105.0 Hz); 131.91;
131.73; 130.83; 128.69; 125.70 (d, JPÃC 97.1 Hz); 34.56
(d, JPÃC 14 Hz); 30.62; 25.80; 22.32; 13.59. HRMS
Na]
/
81 8C
1H-NMR (200 MHz, CDCl3): dꢂ
/
8.24 (d, 1H, Jꢂ
16.5 Hz); 5.71 (d, 1H, JPÃH
3.96 (m, 4H); 2.35Á2.28 (m, 5H); 1.42Á
1.23 (m, 10H); 0.84 (t, 3H, 6.9 Hz). 13C-NMR (50 MHz,
CDCl3) dꢂ198.86; 155.65 (d, JPÃC 4.1 Hz); 139.41 (d,
8.9 Hz); 139.04; 131.44; 129.31; 120.50 (d,
182.8 Hz); 119.01; 61.26 (d, JPÃC 5.5 Hz);
19.9 Hz); 30.08, 25.85; 21.90; 15.85 (d,
6.1 Hz); 13.26. HRMS Calc. for C14H25O4P
/
/
8.46 (d, 1H, Jꢂ
/
16.5 Hz); 6.22 (d, 1H, Jꢂ
/
ꢂ
/
ꢂ
/
14.5 Hz); 4.1Á
/
/
/
/
/
ꢂ
/
/
JPÃC
JPÃC
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
33.75 (d, JPÃC
JPÃC
(Mꢂ
ꢂ
/
ꢂ
/
ꢂ
/
Calc. for C22H25O2P [Mꢀ
/
Na]: 375.1489; [Mꢀ
/
/
Na): 311.1388; [Mꢀ
/
Na] Found: 311.1376. IR
Found: 375.1480. IR (KBr; cmꢃ1): 3060, 2956, 2927,
2851, 2188, 1707, 1669, 1555, 1431, 1255, 1174, 1112,
688.
(Film; cmꢃ1): 2956, 2927, 2865, 1674, 1569, 1459,
1359, 1231, 1016, 954, 830, 778.
3.3.5. Compound 2e: m.p. 101Á
1H-NMR (200 MHz, CDCl3): dꢂ
13.6 Hz); 7.79 (d, 1H, Jꢂ 13.6 Hz); 7.63Á
6.85 (d, 1H, JPÃH
47.2 Hz). 13C-NMR (50 MHz,
CDCl3) dꢂ161.74 (d, JPÃC 3.0 Hz); 141.52 (d,
JPÃC 5.2 Hz); 133.81 (d, JPÃC 146.9 Hz); 130.88;
130.75; 130.66; 130.55; 128.61; 128.40; 128.35; 128.28;
128.06; 120.36 (d, JPÃC 102.7 Hz); 105.27 (d, JPÃC
28.8 Hz). HRMS Calc. for C28H23OP [MꢀNa]:
429.1384; [Mꢀ
Na] Found: 429.1378. IR (KBr; cmꢃ1):
/
102 8C
7.83 (d, 1H, Jꢂ
7.01 (m, 20H);
/
/
Acknowledgements
/
/
ꢂ
/
The authors thank the following agencies for support:
CNPq, FAPERGS and CAPES.
/
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
ꢂ
/
References
/
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/
3053, 3023, 2919, 2849, 2177, 1560, 1490, 1440, 1345,
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hedron Lett. 20 (1979) 2757;
3.3.6. Compound 2f: m.p. 95Á
1H-NMR (200 MHz, CDCl3): dꢂ
7.59Á7.31 (m, 11H), 7.22 (d, 1H, 7.6 Hz); 7.09 (d, 1H,
7.6 Hz); 6.79 (d, 1H, JPÃH
18.4 Hz), 2.03 (s, 3H). 13C-
NMR (50 MHz, CDCl3) dꢂ198.9; 165.30 (d, JPÃC 2.7
Hz); 141.12 (d, JPÃC 9.1 Hz); 133.87 (d, JPÃC 105.6
Hz); 132.00; 131.89 (d, JPÃC 9.9 Hz); 131.77; 130.53;
130.42; 130.26; 129.79; 129.02; 128.43 (d, JPÃC 5.8 Hz);
32.41. HRMS Calc. for C24H21O2P [MꢀNa]: 395.1176;
[Mꢀ
Na] Found: 395.1227. IR (KBr; cmꢃ1): 3083, 3063,
/
96 8C
/
7.93Á7.38 (m, 4H);
/
/
ꢂ
/
(g) S.D. Darling, F.N. Muralidharan, V.B. Muralidharan, Tetra-
hedron Lett. 20 (1979) 2761.
/
ꢂ
/
ꢂ
/
ꢂ
/
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/
(b) J. Rokach, Y. Guindon, R.N. Young, J. Adams, J.G. Atkinson,
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ꢂ
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