Application of 1-(α-aminobenzyl)-2-naphthols as air-stable ligands for pd-catalyzed Mizoroki-Heck coupling reaction

Article abstract of DOI:10.1080/00397911.2010.544439

Air-stable, easily accessible Mannich bases, 1-(α-aminobenzyl)-2- naphthols, are used as ligands in palladium-catalyzed Mizoroki-Heck reaction on a variety of substrates. High turnover numbers are observed for both the reactions with aryl bromides and iodides, while aryl chlorides are inert. Copyright Taylor & Francis Group, LLC.

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Application of 1-(α-Aminobenzyl)-2-
naphthols as Air-Stable Ligands for
Pd-Catalyzed Mizoroki–Heck Coupling
Reaction
Anju R. Chaudhary a & Ashutosh V. Bedekar a
a Faculty of Science, Department of Chemistry, Maharaja Sayajirao
University of Baroda, Vadodara, India
Accepted author version posted online: 17 Nov 2011.Version of
record first published: 27 Feb 2012.
To cite this article: Anju R. Chaudhary & Ashutosh V. Bedekar (2012): Application of 1-(α-
Aminobenzyl)-2-naphthols as Air-Stable Ligands for Pd-Catalyzed Mizoroki–Heck Coupling Reaction,
Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic
Chemistry, 42:12, 1778-1785
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Synthetic Communications1, 42: 1778–1785, 2012
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.544439
APPLICATION OF 1-(a-AMINOBENZYL)-2-NAPHTHOLS
AS AIR-STABLE LIGANDS FOR Pd-CATALYZED
MIZOROKI–HECK COUPLING REACTION
Anju R. Chaudhary and Ashutosh V. Bedekar
Faculty of Science, Department of Chemistry, Maharaja Sayajirao
University of Baroda, Vadodara, India
GRAPHICAL ABSTRACT
Abstract Air-stable, easily accessible Mannich bases, 1-(a-aminobenzyl)-2-naphthols, are
used as ligands in palladium-catalyzed Mizoroki–Heck reaction on a variety of substrates.
High turnover numbers are observed for both the reactions with aryl bromides and iodides,
while aryl chlorides are inert.
Keywords 1-(a-Aminobenzyl)-2-naphthols; Mizoroki–Heck; phosphine-free ligands
INTRODUCTION
Palladium-catalyzed attachment of vinyl moiety to aryl halides, often referred
as the Mizoroki–Heck reaction, is an extremely useful and routinely employed
method of formation of carbon–carbon bonds.[1,2] This exceptional reaction has
been topic of extensive research in different laboratories of academic or industrial
chemistry, and the results are accessible in a number of reviews.[3–5] Most commonly,
an appropriate aryl halide is treated with Pd catalyst, preferably as a complex with a
suitable ligand,[6–8] an olefin, and an appropriate base to furnish a substituted new
alkene.
Most of the examples of Mizoroki–Heck reactions are usually carried out in
the presence of phosphine ligands in an inert atmosphere. However, phosphine
ligands are either expensive or difficult to prepare, are often toxic, and are air sensi-
tive. For this reason, there is a need to find a phosphine-free and inexpensive ligand
for these important reactions. In particular, there are some N,N-ligands reported in
Received August 16, 2010.
Address correspondence to Ashutosh V. Bedekar, Faculty of Science, Department of Chemistry,
Maharaja Sayajirao University of Baroda, Vadodara 390 002, India. E-mail: avbedekar@yahoo.co.in
1778

1-(a-AMINOBENZYL)-2-NAPHTHOLS
1779
the recent literature, and these have shown varying degrees of activity as palladium
catalyst system in the two reactions.[9–14] There is a further scope to find more effec-
tive combination of simple N,N-ligands and palladium catalyst for this important
reaction. In this communication, we present our findings where easily accessible
1-(a-aminobenzyl)-2-naphthols 1 were used as efficient phosphine-free ligands for
this palladium-catalyzed reaction.
RESULTS AND DISCUSSION
Condensation of 1o or 2o amines with aldehydes and 2-naphthols similar to the
classical Mannich reaction gives 1-(a-aminobenzyl)-2-naphthols
1 in good
yields.[15,16] The so-called Betti base is formed when ammonia (as the amine) is con-
densed with 2-naphthol and benzaldehyde.[17,18] Some of the molecules with struc-
tures similar to 1 have been studied from different aspects and results are reported
in the literature:[19–21]
Compound 1 has an attractive arrangement of two heteroatoms (N and O) at a
suitable distance to form a six-member stable chelate with metal ions, a prerequisite
for applications as ligand in metal-catalyzed reactions, and few of them are available
in the literature.[22–27] In the present communication, we present our results when
such ligands are used for palladium-catalyzed Heck reaction. A small group of these
ligands 1a to 1c with 2o amines and 1d and 1e with 1o amines are prepared for this
study; see Scheme 1.
Scheme 1. List of ligands prepared and scanned.

1780
A. R. CHAUDHARY AND A. V. BEDEKAR
Table 1. Search for suitable conditions for Heck reaction with 1-(a-aminobenzyl)-2-naphthols 1 as ligand
No.
ArX
Ligand=Pd(OAc)2 (mol% ratio)
Solvent
Yield (%) of 4 (TON)c
1
2
2a
2b
2c
2c
2c
2c
2c
2c
2c
2c
2c
2c
2c
2c
1a (1.2=1.0)a
DMA
DMA
DMA
DMA
DMA
DMA
DMA
DMF
NMP
DMA
DMA
DMA
DMA
DMA
No reaction [—]
60 [597]
96 [194]
93 [187]
87[175]
1a (0.12=0.10)
1a (0.55=0.50)
1b (0.55=0.50)
1c (0.55=0.50)
1d (0.55=0.50)
1e (0.55=0.50)
1a (0.55=0.50)
1a (0.55=0.50)
1a (0.12=0.10)
1a (0.012=0.010)
1a (0.006=0.005)
1a (0.12=0.10)b
1a (0.55=0.25)
3
4
5
6
84 [170]
86 [173]
89[180]
7
8
9
69 [139]
97 [975]
79 [7890]
68 [13594]
89 [889]
97 [390]
10
11
12
13
14
Note. Compound 4 (Ar & Ar0 ¼ Ph). All reactions run with K2CO3 (2.5 eq.) at 140 ꢀC for 40 h, except
entry 13.
aWith TBAB (0.25 eq.).
bWith NEt3 (2.5 eq.).
cTON–turn over number.
The series of ligands we are then tested for standard Heck conditions, and the
results are presented in Table 1:
The present ligands prepared either from 1o or 2o amines are very effective for
the Heck reaction with either K2CO3 or with organic amine Et3N, and the stilbene is
obtained almost as a single trans isomer. As expected, chlorobenzene 2a was inert
even in the presence of tetrabutylammonium bromide (TBAB) as additive for this
reaction, while iodobenzene 2c is more reactive than bromobenzene 2b. We varied
the amount of catalyst to as low as 0.005 (mol% Pd), and stilbene was isolated in
moderate yield with excellent turnover number.
Solvent study indicated dimethylacetamide (DMA) or dimethylformamide
(DMF) to be good solvents, and all the ligands were almost equally efficient in the
reaction. The effect of the ligand is ascertained by a separate experiment with rela-
tively less-reactive bromobenzene 2b. The reaction with ligand 1a under controlled
conditions and without any ligand with Pd(OAc)2 under identical conditions clearly
shows increase in the conversion and yield of trans-stilbene in the former (see Fig 1).
A number of different derivatives 5 to 9 of stilbene are prepared by using
ligand–Pd ratio (1a=Pd(OAc)2 ¼ 0.12=0.10 mol%) while for 10 a greater ratio of styr-
ene (6 eq.) and catalyst was needed (1.65=1.5 mol%). It is noteworthy that we were
able to prepare 1,3,5-tris(styryl)-benzenes 10 in good yields compared to other
olefination methods[28–35] (Scheme 2).

1-(a-AMINOBENZYL)-2-NAPHTHOLS
1781
Figure 1. Effect of ligand on the Mizoroki–Heck reaction of 2b. Pd(OAc)2 (0.1%), 1a (0.12%), K2CO3 (2.5
eq.), styrene (1.5 eq.) in DMA at 100 ꢀC for the specified time. Yields are isolated ones.
Scheme 2. Examples of Mizoroki–Heck reaction.
The well-established catalytic cycle of the Heck reaction starts with reduction
of Pd(II) to Pd(0), often referred to as preactivation, followed by oxidative addition
of arylhalide, insertion of olefin, and finally reductive elimination.[5,6] In the case of
phosphine-free reaction conditions, it is possible that the initial reduction of pal-
ladium during preactivation is assisted by nucleophilic amine of the ligands rather
from alkene.
EXPERIMENTAL
All reactions were carried out using standard bench-top laboratory techniques
and using commercial-grade reagents and solvents. Solvents such as DMA, DMF,

1782
A. R. CHAUDHARY AND A. V. BEDEKAR
and N-methyl-2-pyrrolidone (NMP) were purified according to the standard pro-
cedure. 1H NMR spectra were recorded in chloroform-D3 at 400 MHz using Bruker
Avance-II spectrometer. Infrared (IR) spectra were recorded as KBr pallet on a
Perkin Elmer RXI spectrometer. Purification of reaction products was carried out
by column chromatography using silica gel (60–120 mesh) using light petroleum
ether and ethyl acetate as eluent. Thin-layer chromatography (TLC) was performed
on silica gel 60 F254 (Merck), and melting points were recorded in capillary tubes
heated slowly in paraffin oil and are uncorrected. All the products of Mizoroki–Heck
reaction are known compounds, and their structures were established by comparing
the mp and mass spectra or NMR spectra with the reported values.
Method A for the Preparation of 1a
A solution of b-naphthol (1.0 g, 6.93 mmol) and benzaldehyde (0.74 g,
6.93 mmol) was prepared in absolute alcohol (2 mL). Piperidine (0.59 g, 6.93 mmol)
was slowly added to this solution, and the mixture was stirred for 48 h at room tem-
perature. The solid was filtered off and washed twice with cold ethyl alcohol
(2 ꢁ 3 mL). It was recrystallized from a mixture of petroleum ether and ethyl acetate
to get colorless crystals of 1a (1.02 g, 46%), mp ¼ 195–198 ꢀC (lit.[16] 198–199 ꢀC).
Method B for the Preparation of 1a
Alternatively, this mixture of b-naphthol, benzaldehyde, and piperidine (same
quantities as A) was stirred at 60 ꢀC for 24 h under a nitrogen atmosphere. The reac-
tion mixture was dispersed at room temperature with ethanol (5 ml). The white solid
was separated, collected, and washed with cold ethanol (2 ꢁ 3 mL). The crystalline
white residue was purified by recrystallization from a mixture of petroleum ether
and ethyl acetate to get 1a (1.37 g, 62%); mp ¼ 196–198 ꢀC (lit.[16] 198–199 ꢀC).
IR (KBr) t: 3459, 3065, 2971, 2939, 1599, 1519, 1491, 1238, 1155, 1035,
717 cmꢂ1. H NMR (400 MHz, CDCl3) d 1.70–2.17 (m, 8H), 2.68 (br s, 1H), 3.34
(br s, 1H), 5.10 (s, 1H), 7.17–7.38 (m, 6H), 7.56 (d, 6.1 Hz, 2H), 7.66 (d, 8.8 Hz,
1H), 7.68–7.77 (dd, 8.08 & 0.8 Hz, 1H), 7.83 (d, 8.6 Hz, 1H), 13.84 (br s, 1H).
Important Analytical Data for Other Ligands
Compound 1b. Prepared by procedure A: 46.4% yield mp ¼ 176–179 ꢀC
(lit.[16] 181–183 ꢀC).
IR (KBr) t: 3465, 3057, 2971, 2841, 1618, 1593, 1515, 1411, 1315, 1238, 1157,
1028, 869, 824, 746 cmꢂ1. H NMR (400 MHz, CDCl3) d 2.30–2.45 (m, 3H), 3.13 (br
s, 1H), 3.6–3.82 (m, 4H), 5.14 (s, 1H), 7.16 (d, 8.84 Hz, 1H), 7.19–7.44 (m, 5H), 7.58
(d, 7.64 Hz, 2H), 7.66–7.71 (m, 2H), 7.84 (d, 8.56 Hz, 1H), 13.07 (s, 1H).
Compound 1c. Prepared by procedure A: 71.4% yield mp ¼ 162–164 ꢀC
(lit.[15] 164–164.5 ꢀC).
IR (KBr) t 3270, 3057, 2991, 2953, 2858, 1599, 1517, 1409, 1374, 1351, 1238,
1161, 1033, 870, 704 cmꢂ1. H NMR (500 MHz, CDCl3) d: 2.34 (br s, 6H), 4.84 (s,
1H), 7.15–7.16 (d, 8.7 Hz, 1H), 7.18–7.28 (m, 4H), 7.34–7.39 (m, 1H), 7.58 (d,

1-(a-AMINOBENZYL)-2-NAPHTHOLS
1783
7.5 Hz, 2H), 7.66 (d, 8.9 Hz, 1H), 7.68–7.70 (d, 7.95 Hz, 1H), 7.85 (d, 8.6 Hz, 1H),
13.76 (s, 1H).
Compound 1d. Prepared by procedure B: 30% yield mp ¼ 134–136 ꢀC (lit.[18]
136–137 ꢀC).
IR (KBr) t: 3325, 3025, 1619, 1598, 1515, 1413, 1384, 1344, 1270, 1239, 1156,
1073, 1027, 861, 827 cmꢂ1. H NMR (400 MHz, CDCl3) d 3.83 (d, 12.9 Hz, 1H), 4.05
(d, 12.9 Hz, 1H), 5.76 (s, 1H), 7.19–7.39 (m, 13H), 7.66–7.69 (d, 8.52 Hz, 1H),
7.73–7.76 (m, 2H), 13.26 (br s, 1H).
Compound 1e. Prepared by procedure B: 81.2% yield mp ¼ 154–156 ꢀC
(lit.[19] 155–156 ꢀC).
IR (KBr) t 3275, 3059, 3025, 2963, 1622, 1414, 1379, 1270, 1237, 1077, 743,
699 cmꢂ1. H NMR (400 MHz, CDCl3) d: 1.5 (d, 6.8 Hz, 3H), 2.28 (br m, 1H), 3.89
(q, 6.8 Hz, 1H), 5.45 (s, 1H), 7.17–7.75 (m, 16 H), 13.72 (s, 1H).
Typical Procedure for the Heck Reaction (Table 1, No. 11)
A solution of palladium acetate (0.055 mg, 0.000245 mmol) and ligand 1a
(0.093 mg, 0.000294 mmol) was made in dry dimethylacetamide (2 mL) under the
nitrogen atmosphere. This was sonicated for 2–3 min to degas and to make the
solution homogeneous. In another two-necked flask, a mixture of iodobenzene
(0.5 g, 2.45 mmol), dry potassium carbonate (0.85 g, 6.13 mmol), and dry dimethyla-
cetamide (5 mL) was made and heated under a nitrogen atmosphere. When the tem-
perature attained 60 ꢀC, styrene (0.38 g, 3.7 mmol) was slowly introduced by syringe.
The mixture was then heated to 100 ꢀC and the previously prepared catalyst solution
was added. The temperature was further raised to 140 ꢀC and continued for another
40 h. The reaction mixture was quenched with water, neutralized using aqueous HCl
(6 N, 5 mL), and extracted with dichloromethane (3 ꢁ 25 mL). The combined organic
phase was washed with water and dried over anhydrous sodium sulfate. Solvent was
removed in vacuum, and the crude product was purified by column chromatography
on silica gel to afford trans-stilbene (0.35 g, 79%). mp ¼ 120–122 ꢀC.
CONCLUSION
We report novel use of readily available and air-stable 1-(a-aminobenzyl)-2-
naphthols as phosphine-free ligands for efficient palladium-catalyzed Mizoroki–
Heck reaction of aryl bromides=iodides.
ACKNOWLEDGMENTS
We thank the Council of Scientific and Industrial Research (CSIR), New
Delhi, for the award of a research fellowship to A. R. C. We are grateful to B. V.
Kamath for his support and S. P. Sahoo of Sun Pharmaceutical Advanced Research
Center for recording some of the NMR spectra.

1784
A. R. CHAUDHARY AND A. V. BEDEKAR
REFERENCES
1. Mizoroki, T.; Mori, K.; Ozaki, A. Arylation of olefins with aryl iodide catalyzed by
palladium. Bull. Chem. Soc. Jpn. 1971, 44, 581.
2. Heck, R. F.; Nolly, J. P. Palladium-catalyzed vinylic hydrogen substitution reactions with
aryl, benzyl, and styryl halides. J. Org. Chem. 1972, 37, 2320–2322.
3. Heck, R. F. Palladium-catalyzed reactions of organic halides with olefins. Acc. Chem. Res.
1979, 12, 146–151.
4. De Meijere, A.; Meyer, F. E. Fine feathers make fine birds: The Heck reaction in modern
garb. Angew. Chem. Int. Ed. 1994, 33, 2379–2411.
5. Beletskaya, I. P.; Cheprakov, A. V. The Heck reaction as a sharpening stone of palladium
catalysis. Chem. Rev. 2000, 100, 3009–3066.
6. Bedford, R. B.; Cazin, C. S. J.; Holder, D. The development of palladium catalysts for
C-C and C-heteroatom bond-forming reactions of aryl chloride substrates. Coord. Chem.
Rev. 2004, 248, 2283–2321.
7. Amatore, C.; Jutand, A. Anionic Pd(0) and Pd(II) intermediates in palladium-catalyzed
Heck and cross-coupling reactions. Acc. Chem. Res. 2000, 33, 314–321.
8. Herrmann, W. A. N-Heterocyclic carbenes: A new concept in organometallic catalysis.
Angew. Chem. Int. Ed. 2002, 41, 1290–1309.
9. Hermann, W. A.; Ofele, K.; von Preysing, D.; Schneider, S. K. Phospha-palladacycles
and N-heterocyclic carbene palladium complexes: Efficient catalysts for C-C coupling
reactions. J. Organomet. Chem. 2003, 687, 229–248.
10. Farina, V. High-turnover palladium catalysts in cross-coupling and Heck chemistry: A
critical overview. Adv. Synth. Catal. 2004, 346, 1553–1582.
´
11. Botella, L.; Najera, C. Mono- and b,b-double-Heck reactions of a,b-unsaturated carbonyl
compounds in aqueous media. J. Org. Chem. 2005, 70, 4360–4369.
12. Eisnor, C. R.; Gossage, R. A.; Yadav, P. N. Oxazoline chemistry, part 11: Synthesis of
natural and synthetic isoflavones, stilbenes, and related species via C-C bond formation
promoted by a Pd-ozaxoline complex. Tetrahedron 2006, 62, 3395–3401.
13. Mino, T.; Shirae, Y.; Sasai, Y.; Sakemoto, M.; Fujita, T. Phosphine-free palladium
catalyzed Mizoroki–Heck reaction using hydrazone as a ligand. J. Org. Chem. 2006, 71,
6834–6839.
14. Herrmann, W. A.; Elison, M.; Fischer, J.; Kosher, C.; Artus, G. R. J. Metal complexes of
N-heterocyclic carbenes—A new structural principle for catalysts in homogeneous
catalysis. Angew. Chem., Int. Ed. 1995, 34, 2371–2374.
15. Littman, J. B.; Brode, W. R. Condensations of secondary amines with aldehydes and
naphthols. J. Am. Chem. Soc. 1930, 52, 1655–1659.
16. Paul, N. K.; Dietrich, L.; Jha, A. Convenient synthesis of 1-arylmethyl-2-naphthols.
Synth. Commun. 2007, 37, 877–888.
17. Betti, M. Condensation between b-naphthol, aldehydes, and amines. Gazz. Chim. Ital.
1900, 30, 310–316.
18. Cardellicchio, C.; Ciccarella, G.; Naso, F.; Schingaro, E.; Scordari, F. The Betti base:
Absolute configuration and routes to a family of related chiral nonracemic bases.
Tetrahedron: Asymmetry 1998, 9, 3667–3675.
19. Cimarelli, C.; Mazzanti, A.; Palmieri, G.; Volpini, E. Solvent-free asymmetric aminoalk-
ylation of electron-rich aromatic compounds: Stereoselective synthesis of aminoalkyl-
naphthols by crystallization-induced asymmetric transformation. J. Org. Chem. 2001,
66, 4759–4765.
´
´ ´
20. Szatmari, I.; Martinek, T. A.; Lazar, L.; Fulo¨p, F. Substituent effects in the ring-chain
¨
tautomerism of 1,3-diaryl-2,3-dihydro-1H-naphth[1.2-e][1.3]oxazines. Tetrahedron 2003,
59, 2877–2884.

1-(a-AMINOBENZYL)-2-NAPHTHOLS
1785
´
21. Szatmari, I.; Fulo¨p, F. Synthesis and transformations of 1-(a-aminobenzyl)-2-naphthol
¨
derivatives. Curr. Org. Synth. 2004, 1, 155–165.
22. Palmieri, G. A practical o-hydroxybenzylamines-promoted enantioselective addition of
dialkylzinc to aldehydes with asymmetric amplification. Tetrahedron: Asymmetry 2000,
11, 3361–3373.
23. Liu, D.-X.; Zhang, L.-C.; Wang, Q.; Da, C.-S.; Xin, Z.-Q.; Wang, R.; Choi, M. C. K.
Chan, A. S. C. The application of chiral aminonaphthols in the enantioselective addition
of diethylzinc to aryl aldehydes. Org. Lett. 2001, 3, 2733–2735.
24. Lu, J.; Xu, X.; Wang, S.; Wang, C.; Hu, Y.; Hu, H. Novel preparation of non-racemic
1-[a-(1-azacycloalkyl)benzyl]-2-naphthols from Betti base and their application as chiral
ligands in the asymmetric addition of diethylzinc to aryl aldehydes. J. Chem. Soc., Perkin.
Trans. 1, 2002, 2900–2903.
25. Lu, J.; Xu, X.; Wang, C.; He, J.; Hu, Y.; Hu, H. Synthesis of chiral ligands derived from
the Betti base and their use in the enantioselective addition of diethylzinc to aromatic
aldehydes. Tetrahedron Lett. 2002, 43, 8367–8369.
26. Cimarelli, C.; Palmieri, G.; Volpini, E. A practical stereoselective synthesis of secondary
and tertiary aminonaphthols: Chiral ligands for enantioselective catalysts in the addition
of diethylzinc to benzaldehyde. Tetrahedron: Asymmetry 2002, 13, 2417–2426.
´
27. Szatmari, I.; Sillanpa¨a¨, R.; Fulo¨p, F. Microwave-assisted, highly enantioselective addition
¨
of diethylzinc to aromatic aldehydes catalyzed by chiral aminonaphthols. Tetrahedron:
Asymmetry 2008, 19, 612–617.
28. Winter, W.; Langjahr, U.; Meier, H.; Merkuschew, J.; Juriew, J. Photochemie des
1,3,5-tristyrylbenzols. Chem. Ber. 1984, 117, 2452–2463.
´
´
´
´
´
29. Dıez-Barra, E.; Garcıa-Martınez, J. C.; Merino, S.; del Rey, R.; Rodrıguez-Lopez, J.;
´
´
Sanchez-Verdu, P.; Tejedac, J. Synthesis, characterisation, and optical response of dipolar
and non-dipolar poly(phenylenevinylene)dendrimers. J. Org. Chem. 2001, 66, 5664–5670.
30. Dawood, K. M. Microwave-assisted Suzuki–Miyaura and Heck–Mizoroki cross-coupling
reactions of aryl chlorides and bromides in water using stable benzothiazole-based
palladium(II) precatalysts. Tetrahedron 2007, 63, 9642–9651.
31. Heynekamp, J. J.; Weber, W. M.; Hunsaker, L. A.; Gonzales, A. M.; Orlando, R. A.;
Deck, L. M.; Van der Jagt, D.L. Substituted trans-stilbenes, including analogues of the
natural product resveratrol, inhibit the human tumor necrosis factor a-induced activation
of transcription factor nuclear factor jB. J. Med. Chem. 2006, 49, 7182–7189.
32. Alacid, E.; Najera, C. P. Palladium-catalyzed cross-coupling reactions of potassium
alkenyltrifuloroborates with organic halides in aqueous media. J. Org. Chem. 2009, 74,
2321–2327.
33. Wan, P.; Davis, M. J.; Teo, M. A. Photoaddition of water and alcohols to 3-nitrostyrenes:
Structure–reactivity and solvent study. J. Org. Chem. 1989, 54, 1354–1359.
34. Lansky, A.; Reiser, O.; De Meijere, A. Highly efficient alkene-alkene coupling reactions
with vicinal dibromides. Synlett 1990, 7, 405–407.
35. Cella, R.; Stefani, H. A. Ultrasound-assisted synthesis of Z and E-stilbenes by Suzuki
cross-coupling reactions of organotellurides with potassium organotrifluoroborate salts.
Tetrahedron 2006, 62, 5656–5662.