Heck reactions of aryl bromides with alk-1-en-3-ol derivatives catalysed by a tetraphosphine/palladium complex

Article abstract of DOI:10.1016/j.tetlet.2004.05.117

cis,cis,cis-1,2,3,4-Tetrakis(diphenylphosphinomethyl)cyclopentane/ [PdCl(C₃H₅)]₂ efficiently catalyses the Heck reaction of alk-1-en-3-ol with a variety of aryl bromides. In the presence of hex-1-en-3-ol or oct-1-en-3-ol, the β-arylated carbonyl compounds were selectively obtained. Linalool and 2-methylbut-3-en-2-ol led to the corresponding 1-arylalk-1-en-3-ol derivatives. Turnover numbers up to 69,000 can be obtained for this reaction. A minor electronic effect of the substituents of the aryl bromide was observed. Similar reaction rates were observed in the presence of activated aryl bromides such as bromoacetophenone and deactivated aryl bromides such as bromoanisole.

Full text of DOI:10.1016/j.tetlet.2004.05.117

Tetrahedron
Letters
Tetrahedron Letters 45 (2004) 5633–5636
Heck reactions of aryl bromides with alk-1-en-3-ol derivatives
catalysed by a tetraphosphine/palladium complex
Florian Berthiol, Henri Doucet* and Maurice Santelli*
Laboratoire de Synthꢀese Organique, UMR 6180 CNRS and Universitꢁe d’Aix-Marseille III: ‘Chirotechnologies: catalyse et biocatalyse’,
Facultꢁe des Sciences de Saint Jꢁer^ome, Avenue Escadrille Normandie-Niemen, 13397 Marseille Cedex20, France
Received 23 March 2004; revised 24 May 2004; accepted 24 May 2004
Abstract—cis,cis,cis-1,2,3,4-Tetrakis(diphenylphosphinomethyl)cyclopentane/[PdCl(C3H5)]2 efficiently catalyses the Heck reaction
of alk-1-en-3-ol with a variety of aryl bromides. In the presence of hex-1-en-3-ol or oct-1-en-3-ol, the b-arylated carbonyl com-
pounds were selectively obtained. Linalool and 2-methylbut-3-en-2-ol led to the corresponding 1-arylalk-1-en-3-ol derivatives.
Turnover numbers up to 69,000 can be obtained for this reaction. A minor electronic effect of the substituents of the aryl bromide
was observed. Similar reaction rates were observed in the presence of activated aryl bromides such as bromoacetophenone and
deactivated aryl bromides such as bromoanisole.
Ó 2004 Elsevier Ltd. All rights reserved.
The palladium-catalysed Heck vinylation reaction is one
of the most powerful methods for the formation of C–C
bonds.1 The efficiency of several catalysts for the reac-
tion of aryl halides with acrylates or styrene derivatives
has been studied in detail.2 On the other hand, the
reaction in the presence of alk-1-en-3-ol has attracted
less attention. Moreover, most of the results described
with these alkenes were obtained in the presence of
expensive aryl iodides.3 Few results have been described
in the presence of aryl bromides.4–7 The reaction of alk-
1-en-3-ol and aryl bromides can be performed with a Pd/
triphenylphosphine catalyst, but the palladium com-
plexes formed with this ligand are generally not very
efficient in terms of substrate/catalyst ratio.4 This reac-
tion also proceeds in the presence of Pd(OAc)2 or PdCl2
without added ligand, but 5% catalyst were used.5;6 In
recent years, a more efficient catalyst has been tested
with these substrates by Calo et al. They described that a
Pd-benzothiazole carbene complex catalyses the reac-
tion of but-1-en-3-ol, pent-1-en-3-ol or oct-1-en-3-ol
with aryl bromides in the presence of 1% catalyst.7 If
monophosphine or carbene ligands have been success-
fully used for the reaction with these alkenes, to the best
of our knowledge, the efficiency of tetraphosphine
ligands has not been demonstrated.
In order to obtain stable and efficient palladium
catalysts, we have prepared the new tetraphosphine
ligand,
cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphino-
methyl)-cyclopentane or tedicyp8 (Fig. 1) in which four
diphenylphosphino groups are stereospecifically bound
to the same face of a cyclopentane ring. We have already
reported the results obtained in allylic substitution,8 for
Suzuki cross-coupling9 and for Sonogashira alkynyl-
ation10 using tedicyp as the ligand. We have also
reported several results for Heck vinylation.11 In order
to further establish the requirements for a successful
Heck reaction with our catalyst, we herein report on the
reaction of aryl bromides with alk-1-en-3-ol derivatives.
For this study, based on previous results,11 DMF was
chosen as the solvent and K2CO3 as the base. The
reactions were performed at 130 °C under argon in the
presence of a 1:2 ratio of [Pd(C3H5)Cl]2/tedicyp as cat-
alyst.
Ph2P
Ph2P
PPh2
PPh2
Keywords: Palladium; Catalysis; Heck reaction; Tetraphosphine.
* Corresponding authors. Tel.: +33-4-91-28-84-16; fax: +33-4-91-98-
38-65 (H.D.); tel.: +33-4-91-28-88-25 (M.S.); e-mail addresses: henri.
doucet@univ.u-3mrs.fr; m.santelli@univ.u-3mrs.fr
Tedicyp
Figure 1.
0040-4039/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2004.05.117

5634
F. Berthiol et al. / Tetrahedron Letters 45 (2004) 5633–5636
We first studied the reactivity of hex-1-en-3-ol with
several aryl halides in the presence of 0.1–0.001 mol %
catalyst (Scheme 1, Table 1). It is known that the Heck
reaction in the presence of alk-1-en-3-ol often leads to
the formation of b-arylated ketones.3a With our catalyst,
these ketones were obtained selectively in all cases
indicating that the Pd-tedicyp catalyst is probably a
neutral complex favouring b-elimination to form the
corresponding enol rather than the b-aryl allylic alco-
hol.1b We observed that tedicyp-Pd catalyst system is
tolerant of a variety of aryl halides. Surprisingly, iodo-
benzene led to the coupling adduct in a lower turn over
numbers (TON) than the reaction performed in the
presence of 4-t-butylbromobenzene (Table 1, entries 1,
10 and 11). A minor influence of the electronic factors of
the aryl bromide on the reaction rate was also observed.
Similar TONs were observed using activated 4-bromo-
acetophenone and deactivated 4-bromoanisole: 69,000
and 84,000, respectively (Table 1, entries 2, 3, 12 and 13)
indicating that the rate-limiting step of the reaction with
these alkenols is not the oxidative addition of the aryl
bromide. The reaction performed with the ortho-
substituted aryl bromides 2-trifluoromethyl-bromobenz-
ene or 2-methylbromobenzene led to similar TONs of
33,000 and 7500 than the para-substituted arylbromides
(Table 1, entries 14–19).
Very similar reaction rates were obtained for the cou-
pling of aryl bromides with oct-1-en-3-ol (Table 1, en-
tries 22–28).
Heteroaromatic substrates such as 3-bromopyridine, or
bromothiophenes in the presence of hex-1-en-3-ol or
oct-1-en-3-ol also led to the expected adducts in good
yields (Table 1, entries 20, 21, 27 and 28).
Having demonstrated that linear alk-1-en-3-ol deriva-
tives can be reacted efficiently with aryl bromides, we
Pd
H
OH
R2
O
R1
R1
R1
HO
[Pd(C3H5)Cl]2 / tedicyp
R2
β-elimination
R2
X
+
H
DMF, K2CO3, 130 °C
H
R1 = H, Me, tBu, OMe, MeCO, PhCO, CHO, CF3, F
2 = nC3H7, nC5H11
R
Scheme 1.
Table 1. Heck reactions with hex-1-en-3-ol or oct-1-en-3-ol catalysed by the tedicyp-palladium complex (Scheme 1)12
Entry
Aryl halide
Alkene
Ratio substrate/catalyst
Product
Yield
(%)a
1
Iodobenzene
Hex-1-en-3-ol
Hex-1-en-3-ol
Hex-1-en-3-ol
Hex-1-en-3-ol
Hex-1-en-3-ol
Hex-1-en-3-ol
Hex-1-en-3-ol
Hex-1-en-3-ol
Hex-1-en-3-ol
Hex-1-en-3-ol
Hex-1-en-3-ol
Hex-1-en-3-ol
Hex-1-en-3-ol
Hex-1-en-3-ol
Hex-1-en-3-ol
Hex-1-en-3-ol
Hex-1-en-3-ol
Hex-1-en-3-ol
Hex-1-en-3-ol
Hex-1-en-3-ol
Hex-1-en-3-ol
Oct-1-en-3-ol
Oct-1-en-3-ol
Oct-1-en-3-ol
Oct-1-en-3-ol
Oct-1-en-3-ol
Oct-1-en-3-ol
Oct-1-en-3-ol
1000
1000
1-Phenylhexan-3-one
78
85 (100)
(69)
2
4-Bromoacetophenone
4-Bromoacetophenone
4-Bromobenzophenone
4-Bromobenzophenone
4-Trifluoromethylbromobenzene
4-Trifluoromethylbromobenzene
4-Fluorobromobenzene
4-Fluorobromobenzene
t-Buty4l-bromobenzene
4-t-Butylbromobenzene
4-Bromoanisole
1-(4-Acetylphenyl)hexan-3-one
1-(4-Acetylphenyl)hexan-3-one
1-(4-Benzoylphenyl)hexan-3-one
1-(4-Benzoylphenyl)hexan-3-one
1-(4-Trifluorophenyl)hexan-3-one
1-(4-Trifluorophenyl)hexan-3-one
1-(4-Fluorophenyl)hexan-3-one
1-(4-Fluorophenyl)hexan-3-one
1-(4-t-Butylphenyl)hexan-3-one
1-(4-t-Butylphenyl)hexan-3-one
1-(4-Anisyl)hexan-3-one
3
10,000
10,000
100,000
1000
4
91 (100)
(69)
5
6
92 (100)
(83)
7
10,000
1000
8
(100)
84
(97)
9
10,000
1000
1
0
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
10,000
1000
83
(100)
84
4-Bromoanisole
10,000
10,000
100,000
10,000
100,000
1000
1-(4-Anisyl)hexan-3-one
2-Fluorobromobenzene
2-Fluorobromobenzene
2-Trifluoromethylbromobenzene
2-Trifluoromethylbromobenzene
2-Methylbromobenzene
2-Methylbromobenzene
3-Bromopyridine
1-(2-Fluorophenyl)hexan-3-one
1-(2-Fluorophenyl)hexan-3-one
1-(2-Trifluorophenyl)hexan-3-one
1-(2-Trifluorophenyl)hexan-3-one
1-(2-Methylphenyl)hexan-3-one
1-(2-Methylphenyl)hexan-3-one
1-(3-Pyridyl)hexan-3-one
94 (100)
(67)
90 (100)
(33)
93 (100)
(75)
10,000
10,000
100,000
10,000
50,000
10,000
1000
91 (100)
(31)
3-Bromopyridine
1-(3-Pyridyl)hexan-3-one
4-Bromobenzophenone
4-Bromobenzophenone
4-Fluorobromobenzene
4-t-Butylbromobenzene
4-t-Butylbromobenzene
2-Bromothiophene
1-(4-Benzoylphenyl)octan-3-one
1-(4-Benzoylphenyl)octan-3-one
1-(4-Flurophenyl)octan-3-one
1-(4-t-Butylphenyl)octan-3-one
1-(4-t-Butylphenyl)octan-3-one
1-(2-Thiophene)octan-3-one
1-(3-Thiophene)octan-3-one
(100)
80
89 (100)
84 (100)
(62)
10,000
10,000
250
92 (100)
73 (80)
3-Bromothiophene
Conditions: catalyst [Pd(C3H5)Cl]2/tedicyp 1:2 see Ref. 8 ArX (1 equiv), allylic alcohol (2 equiv), K2CO3 (2 equiv), DMF, 20 h, 130 °C, under argon,
isolated yields, ratio substrate/catalyst based on the aryl halide, in a few cases traces of 1-arylalk-1-en-3-ol derivatives were observed.
a Yields in parenthesis correspond to GC and NMR yields.

F. Berthiol et al. / Tetrahedron Letters 45 (2004) 5633–5636
5635
investigated the scope of this coupling reaction using
substituted alk-1-en-3-ol derivatives. We studied the
reactivity of two 3-substituted alk-1-en-3-ols: linalool
and 2-methylbut-3-en-2-ol (Scheme 2, Table 2). With
these substituted alkenols the expected 1-arylalk-1-en-3-
ol 1 or 2 were obtained selectively but slower reactions
were observed than with the unsubstituted alkenol.
Linalool led to the expected the coupling adducts in
TONs of 740-9000. The results presented in Table 2
unfold a minor substituent effect of the aryl bromide on
the reaction rate (Table 2, entries 2–11).
We also studied the influence of ortho-substituents on
the aryl bromide for this reaction. 2-Fluorobromobenz-
ene, 2-trifluoromethylbromobenzene and 2-methyl-
bromo-benzene led to similar TONs than the para-
substituted aryl bromides (Table 2, entries 12–17).
The reactivity of 2-methylbut-3-en-2-ol is very similar to
linalool and the expected 1-aryl-3-methylbut-1-en-3-ol 2
were obtained in good yields and TONs (Table 2, entries
22–29).
In summary, in the presence of the tedicyp/palladium
complex, the Heck vinylation of several aryl bromides
with alk-1-en-3-ol derivatives can be performed with as
little as 0.01mol % catalyst. The products of the reac-
tions depend on the substituents of the alkenes. Addi-
tion to linalool or 2-methylbut-3-en-2-ol led to the
For example, TONs of 8400 can be achieved with this
catalyst for the reaction of linalool with the activated
substrate 4-bromoacetophenone and with the deacti-
vated substrate 4-bromoanisole (Table 2, entries 2, 3, 10
and 11).
R1
R1
R1
Me
R1
Pd
R2
[Pd(C3H5)Cl]2 / tedicyp
130 °C, DMF, K2CO3
β-elimination
Me
OH
Me
OH
or
+
R2
Me
Br
OH
H
H
R1 = H, Me, tBu, OMe, MeCO, CHO, CF3, F
OH
R2 = -CH2CH2CH=C(CH3)2 or Me
1
2
Scheme 2.
Table 2. Heck reactions with linalool or 2-methylbut-3-en-2-ol catalysed by the tedicyp-palladium complex (Scheme 2)12
Entry
Aryl halide
Alkene
Product
Ratio substrate/catalyst
Yield (%)a
1Iodobenzene
Linalool
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
1000
1000
69 (74)
(100)
84
2
4-Bromoacetophenone
4-Bromoacetophenone
4-Bromobenzaldehyde
Linalool
Linalool
Linalool
Linalool
Linalool
Linalool
Linalool
Linalool
Linalool
Linalool
Linalool
Linalool
Linalool
Linalool
Linalool
Linalool
Linalool
Linalool
Linalool
3
10,000
1000
1000
4
78 (83)
93 (100)
(100)
5
4-Trifluoromethylbromobenzene
4-Fluorobromobenzene
4-Fluorobromobenzene
4-t-Butylbromobenzene
4-t-Butylbromobenzene
4-Bromoanisole
6
1000
10,000
1000
7
81 (87)
(100)
90
8
9
10,000
1000
10
11
12
13
14
15
16
17
18
19
20
(100)
4-Bromoanisole
10,000
1000
84
2-Fluorobromobenzene
2-Fluorobromobenzene
2-Trifluoromethylbromobenzene
2-Trifluoromethylbromobenzene
2-Methylbromobenzene
2-Methylbromobenzene
3-Bromopyridine
(100)
10,000
1000
88
91 (100)
(54)
10,000
1000
87 (100)
(69)
10,000
1000
86 (100)
(75)
3-Bromopyridine
2-Bromothiophene
10,000
1000
1000
82 (92)
83 (90)
90 (98)b
93 (100)b
78b
213-Bromothiophene
Linalool
22
23
24
25
26
27
28
29
4-Trifluoromethylbromobenzene
2-Methylbut-3-en-2-ol
2-Methylbut-3-en-2-ol
2-Methylbut-3-en-2-ol
2-Methylbut-3-en-2-ol
2-Methylbut-3-en-2-ol
2-Methylbut-3-en-2-ol
2-Methylbut-3-en-2-ol
2-Methylbut-3-en-2-ol
1000
4-Bromobenzophenone
4-Fluorobromobenzene
4-t-Butylbromobenzene
4-t-Butylbromobenzene
4-Bromoanisole
10,000
1000
250
(97)b
1000
1000
77 (81)b
90 (100)b
(68)b
4-Bromoanisole
2-Methylbromobenzene
10,000
1000
78 (86)b
Conditions: catalyst [Pd(C3H5)Cl]2/tedicyp 1:2 see Ref. 8 ArX (1 equiv), allylic alcohol (2 equiv), K2CO3 (2 equiv), DMF, 20 h, 130 °C, under argon,
isolated yields, ratio substrate/catalyst based on the aryl halide.
a Yields in parenthesis correspond to GC and NMR yields.
b Reactions performed in an autoclave.

5636
F. Berthiol et al. / Tetrahedron Letters 45 (2004) 5633–5636
D.; Tooze, R.; Cole-Hamilton, D. Chem. Commun. 2001,
779.
corresponding 1-aryl-alk-1-en-3-ol 1 or 2. In the pres-
ence of hex-1-en-3-ol or oct-1-en-3-ol the b-arylated
carbonyl compounds were obtained. Higher reactions
rates were observed with the unsubstituted alk-1-en-3-ol.
In general, the rate-limiting step of these reactions does
not seem to be the oxidative addition of the aryl halides.
With these alk-1-en-3-ol derivatives similar reaction
rates were observed in the presence of 4-bromoace-
tophenone or 4-bromoanisole. For this reason, this
method is applicable to the coupling of both electron-
deficient and electron-rich aryl bromides. The rate-lim-
iting step could be the b-elimination of the ArCH2-
CH(Pd)CH(OH)(R) (Scheme 1) and ArCH2CH(Pd)
CMe(OH)(R) (Scheme 2) complexes. The b-elimination
to form the enol is faster but not possible with
3-substituted alk-1-en-3-ols. This would explain the
slower reactions observed with these substituted alke-
nols. Both in terms of substrate/catalyst ratio and
reaction scope, this catalyst is effective for Heck reac-
tions of alk-1-en-3-ol derivatives. Due to the high price
of palladium, the advantage of such low catalyst loading
reactions could become increasingly important for
industrial processes.
3. For examples of Heck reactions of alk-1-en-3-ol deriva-
tives with aryl iodides: (a) Jeffery, T. J. Chem. Soc., Chem.
Commun. 1984, 1287; (b) Schroeder, D. R.; Stermitz, F. R.
Tetrahedron 1985, 41, 4309; (c) Benhaddou, R.; Czernecki,
S.; Ville, G. J. Chem. Soc., Chem. Commun. 1988, 247; (d)
Tao, W.; Nesbitt, S.; Heck, R. F. J. Org. Chem. 1990, 55,
63; (e) Jeffery, T. Tetrahedron Lett. 1991, 32, 2121; (f)
Thompson, M. D.; Torabi, H. Synthesis 1994, 965; (g)
Kang, S.-K.; Jung, K.-Y.; Park, C.-H.; Namkoong, E.-Y.;
€
Kim, T.-H. Tetrahedron Lett. 1995, 36, 6287; (h) Bjornest-
edt, R.; Zhong, G.; Lerner, R. A.; Barbas, C. F., III. J.
Am. Chem. Soc. 1996, 118, 11720; (i) Tonks, L.; Anson,
M. S.; Hellgardt, K.; Mirza, A. R.; Thompson, D. F.;
Williams, J. M. J. Tetrahedron Lett. 1997, 38, 4319; (j)
€
€
Tietze, L. F.; Gorlitzer, J.; Schuffenhauer, A.; Hubner, M.
Eur. J. Org. Chem. 1999, 1075; (k) Leese, M. P.; Williams,
J. M. J. Synlett 1999, 1645; (l) Zhao, H.; Cai, M.-Z.;
Hu, R.-H.; Song, C.-S. Synth. Commun. 2001, 31,
3665.
4. (a) Fumio, Y.; Toshifumi, H.; Masayuki, W.; Mitsuro, S.;
Masanori, S. Heterocycles 1986, 24, 1223; (b) Aslam, M.;
Elango, V.; Davenport, K. G. Synthesis 1989, 869.
5. Goujon, J. Y.; Zammattio, F.; Kirschleger, B. Tetrahe-
dron: Asymmetry 2000, 11, 2409.
ꢁ
6. Bouquillon, S.; Ganchegui, B.; Estrine, B.; Henin, F.;
Muzart, J. J. Organomet. Chem. 2001, 634, 153.
7. Calo, V.; Nacci, A.; Monopoli, A.; Spinelli, M. Eur. J.
Org. Chem. 2003, 1382.
Acknowledgements
We are grateful to Dr. R. Snowden and Firmenich, S. A.
ꢀ
(Geneve, Switzerland) for their support.
ꢀ
8. Laurenti, D.; Feuerstein, M.; Pepe, G.; Doucet, H.;
Santelli, M. J. Org. Chem. 2001, 66, 1633.
9. Feuerstein, M.; Laurenti, D.; Bougeant, C.; Doucet, H.;
Santelli, M. Chem. Commun. 2001, 325.
References and notes
10. Feuerstein, M.; Berthiol, F.; Doucet, H.; Santelli, M. Org.
Biomol. Chem. 2003, 2235.
1. For reviews on the palladium-catalysed Heck reaction see:
(a) Heck, R. F. In Vinyl Substitution with Organopalladium
Intermediates; Trost, B. M., Fleming, I., Eds.; Compre-
hensive Organic Synthesis; Pergamon: Oxford, 1991;
Vol. 4; (b) de Meijere, A.; Meyer, F. Angew. Chem., Int.
Ed. Engl. 1994, 33, 2379; (c) Malleron, J.-L.; Fiaud,
J.-C.; Legros, J.-Y. Handbook of Palladium-Catalysed
Organic Reactions; Academic: London, 1997; (d) Reetz,
M. T. In Transition Metal Catalysed Reactions; Davies, S.
G., Murahashi, S.-I., Eds.; Blackwell Science: Oxford,
1999; (e) Beletskaya, I.; Cheprakov, A. Chem. Rev. 2000,
100, 3009; (f) Withcombe, N.; Hii(Mimi), K. K.; Gibson,
S.. Tetrahedron 2001, 57, 7449; (g) Littke, A.; Fu, G.
Angew. Chem., Int. Ed. 2002, 41, 4176.
11. (a) Feuerstein, M.; Doucet, H.; Santelli, M. J. Org. Chem.
2001, 66, 5923; (b) Feuerstein, M.; Doucet, H.; Santelli,
M. Synlett 2001, 1980; (c) Feuerstein, M.; Doucet, H.;
Santelli, M. Tetrahedron Lett. 2002, 43, 2191; (d) Berthiol,
F.; Feuerstein, M.; Doucet, H.; Santelli, M. Tetrahedron
Lett. 2002, 43, 5625; (e) Berthiol, F.; Doucet, H.; Santelli,
M. Tetrahedron Lett. 2003, 44, 1221; (f) Berthiol, F.;
Doucet, H.; Santelli, M. Synlett 2003, 841; (g) Kondolff, I.;
Doucet, H.; Santelli, M. Tetrahedron Lett. 2003, 44,
8487.
12. As a typical experiment (Table 2, entry 7), the reaction of
4-fluorobromobenzene (1.75 g, 10 mmol), linalool (3.09 g,
20 mmol) and K2CO3 (2.76 g, 20 mmol) at 130 °C over
20 h in dry DMF (10 mL) in the presence of cis,cis,cis-
1,2,3,4-tetrakis(diphenylphosphinomethyl) cyclopentane/
[PdCl(C3H5)]2 complex (0.001mmol) under argon afforded
the corresponding product 1-(4-fluorophenyl)-3,7-di-
methyl-octa-1,6-dien-3-ol after evaporation and filtration
on silica gel in 81% (2.01 g) isolated yield. 1H NMR
(300 MHz, CDCl3): d 7.33 (dd, 2H, J ¼ 8:5 and 5.5 Hz),
6.98 (t, 2H, J ¼ 8:5 Hz), 6.55 (d, 1H, J ¼ 16:1Hz), 6.17 (d,
1H, J ¼ 16:1 Hz), 5.15 (t, 1H, J ¼ 6:8 Hz), 2.15–1.95 (m,
2H), 1.72 (b s, 1H), 1.70–1.65 (m, 2H), 1.67 (s, 3H), 1.58 (s,
3H), 1.36 (s, 3H); 13C NMR (75 MHz, CDCl3): d 162.3 (d,
JC–F ¼ 246:1 Hz), 136.4, 133.2, 132.2, 127.9 (d,
JC–F ¼ 8:0 Hz), 126.0, 124.3, 115.4 (d, JC–F ¼ 21:2 Hz),
73.4, 42.5, 28.4, 25.7, 22.9, 17.7.
2. For recent examples of Heck reactions catalysed by
palladacycles, see: (a) Herrmann, W. A.; Brossmer, C.;
€
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