# Reactivity of bromoselenophenes in palladium-catalyzed direct arylations

Aymen Skhiri, Ridha Ben Salem, Jean-François Soulé, Henri Doucet

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Aymen Skhiri, Ridha Ben Salem, Jean-François Soulé, Henri Doucet. Reactivity of bromoselenophenes in palladium-catalyzed direct arylations. Beilstein Journal of Organic Chemistry, 2017, 13, pp.2862-2868. 10.3762/bjoc.13.278. hal-01709524

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# Reactivity of bromoselenophenes in palladium-catalyzed direct arylations

Aymen Skhiri¹,², Ridha Ben Salem*², Jean-François Soulé*¹ and Henri Doucet*¹

## Full Research Paper

Open Access

Address:
¹Institut des Sciences Chimiques de Rennes, UMR 6226
CNRS-Université de Rennes 1, "Organométalliques: Matériaux et
Catalyse", Campus de Beaulieu, 35042 Rennes, France and
²Laboratoire de Laboratoire de Chimie Organique LR 17ES08,
Université de Sfax, Faculté des Sciences de Sfax, Route de la Soukra
km 4, 3038 Sfax, Tunisia

Email:
Ridha Ben Salem* - ridhabensalem@yahoo.fr; Jean-François Soulé* -
jean-francois.soule@univ-rennes1.fr; Henri Doucet* -
henri.doucet@univ-rennes1.fr

Keywords:
C–H bond activation; catalysis; heteroarenes; palladium; selenophene

Beilstein J. Org. Chem. **2017**, *13*, 2862–2868.
doi:10.3762/bjoc.13.278

Received: 24 August 2017
Accepted: 04 December 2017
Published: 22 December 2017

Associate Editor: M. Rueping

© 2017 Skhiri et al.; licensee Beilstein-Institut.
License and terms: see end of document.

## Abstract

The reactivity of 2-bromo- and 2,5-dibromoselenophenes in Pd-catalyzed direct heteroarylation was investigated. From 2-bromo-selenophene, only the most reactive heteroarenes could be employed to prepare 2-heteroarylated selenophenes; whereas, 2,5-dibromoselenophene generally gave 2,5-di(heteroarylated) selenophenes in high yields using both thiazole and thiophene derivatives. Moreover, sequential catalytic C2 heteroarylation, bromination, catalytic C5 arylation reactions allowed the synthesis of unsymmetrical 2,5-di(hetero)arylated selenophene derivatives in three steps from selenophene.

## Introduction

(Hetero)aryl-substituted selenophenes represent a class of molecules which exhibit useful physical properties, especially for the preparation of artificial photosynthetic systems for solar energy conversion or for thin film transistor applications [1-3]. In most cases, these (hetero)arylated selenophenes are currently prepared through the use of transition-metal-mediated reactions such as Stille [3-9], Suzuki [10-19], or Kumada [20] couplings [21] (Scheme 1a and b). However, all these procedures require the preparation of an organometallic or a boron derivative of one of the coupling partners, and provide an organometallic salt

(MX) as waste. In recent years, the Pd-catalyzed arylation, via a C–H bond activation, of a broad range of heteroaromatics using aryl halides as reaction partners was demonstrated to be particularly effective for the preparation of bi(hetero)aryls [22-31]. Among the reported results, a few examples of Pd-catalyzed direct arylations via the C–H bond activation of selenophenes using aryl halides as coupling partners have been reported [32-35]. Conversely, C–H bond activation methodology was employed in only one case for the preparation of a heteroarylated selenophene from a haloselenophene. Wipf et al. reported

<footnote>* Corresponding author</footnote>
<figure><img src="image_3.png" /></figure>

<figure><img src="image_4.png" /></figure>

<figure><img src="image_5.png" /><figcaption>**Scheme 1:** Reported Pd-catalyzed heteroarylations of bromoselenophenes.</figcaption></figure>

in 2014 that using ethyl oxazole-4-carboxylate as reaction partner, the corresponding 2,5-bis(oxazol-2-yl)selenophene derivative was formed in 45% yield (Scheme 1c) [17]. Moreover, to our knowledge the Pd-catalyzed direct heteroarylation of 2-bromoselenophene has not yet been described. Therefore, the reactivity of 2-bromo- and 2,5-dibromoselenophenes in Pd-catalyzed direct couplings with heteroarenes needed to be investigated.

Herein, we wish to report on the reactivity of 2-bromoselenophene, 2,5-dibromoselenophene and 2-aryl-5-bromoselenophenes in palladium-catalyzed direct heteroarylations with a variety of heteroarenes using a phosphine-free palladium catalyst.

## Results and Discussion

First, we examined the influence of the reaction temperature, using DMA as solvent, KOAc as base and 2 mol % Pd(OAc)₂ as catalyst (Table 1). We had previously observed that these reaction conditions allowed the coupling of several heteroaromatics such as thiazole, pyrrole, furan or imidazole derivatives with aryl bromides [36].

2-Bromoselenophene, which was easily prepared by reaction of selenophene with N-bromosuccinimide [37], and 2-ethyl-4-methylthiazole were employed as model substrates for our study. Reactions performed at 130 °C or 110 °C gave the expected arylated selenophene **1** in 55% and 64% yields, respectively, with complete conversions of 2-bromoselenophene; whereas **1** was obtained in a higher yield of 80% when the reaction was conducted at 90 °C (Table 1, entries 1–3). At elevated temperature (110–130 °C), 2-bromoselenophene seems to afford larger amounts of selenophene oligomers as side-products. The use of PdCl₂ or PdCl(C₃H₅)(dppb) as catalysts instead of Pd(OAc)₂ or other bases such as K₂CO₃, Cs₂CO₃, CsOAc or NaOAc afforded **1** in lower yields (Table 1, entries 4–9). The influence of two other solvents in this cross-coupling reaction was also examined. We observed that both DMF and xylene in the presence of 2 mol % Pd(OAc)₂ catalyst with KOAc gave **1** in moderate yields (Table 1, entries 10 and 11).

<figure><img src="image_6.png" /><figcaption>**Table 1:** Influence of the reaction conditions for the coupling of 2-ethyl-4-methylthiazole with 2-bromoselenophene.ª</figcaption></figure>

<table><thead><tr><th>Entry</th><th>Catalyst</th><th>Solvent</th><th>Base</th><th>Yield (%)</th></tr></thead><tbody><tr><td>1</td><td>Pd(OAc)₂</td><td>DMA</td><td>KOAc</td><td>55<sup>b</sup></td></tr><tr><td>2</td><td>Pd(OAc)₂</td><td>DMA</td><td>KOAc</td><td>64<sup>c</sup></td></tr><tr><td>3</td><td>Pd(OAc)₂</td><td>DMA</td><td>KOAc</td><td>80</td></tr><tr><td>4</td><td>PdCl₂</td><td>DMA</td><td>KOAc</td><td>45</td></tr><tr><td>5</td><td>PdCl(C₃H₅)(dppb)</td><td>DMA</td><td>KOAc</td><td>48</td></tr><tr><td>6</td><td>Pd(OAc)₂</td><td>DMA</td><td>K₂CO₃</td><td>41</td></tr><tr><td>7</td><td>Pd(OAc)₂</td><td>DMA</td><td>Cs₂CO₃</td><td>9</td></tr><tr><td>8</td><td>Pd(OAc)₂</td><td>DMA</td><td>CsOAc</td><td>52</td></tr><tr><td>9</td><td>Pd(OAc)₂</td><td>DMA</td><td>NaOAc</td><td>17</td></tr><tr><td>10</td><td>Pd(OAc)₂</td><td>DMF</td><td>KOAc</td><td>53</td></tr><tr><td>11</td><td>Pd(OAc)₂</td><td>xylene</td><td>KOAc</td><td>48</td></tr></tbody></table>

Then, we investigated the scope of the coupling of 2-bromoselenophene with a set of heteroarenes in the presence of 2 mol % Pd(OAc)₂, KOAc as the base in DMA at 90 °C (Scheme 2). The reaction of 2-isopropyl-4-methylthiazole gave the desired product **2** in 82% yield. Conversely, low yields in the target products **3–5** were obtained for the reactions with thiophene-2-carbonitrile, 2-chlorothiophene and 2-pentylthiophene, although complete conversions of 2-bromoselenophene

<footnote>aConditions: catalyst (0.02 equiv), 2-bromoselenophene (1 equiv), 2-ethyl-4-methylthiazole (1.5 equiv), base (2 equiv), 24 h, 90 °C, isolated yields of **1**. b130 °C, c110 °C.</footnote>
<caption>**Scheme 2:** Palladium-catalyzed heteroarylations of 2-bromoselenophene. *: 110 °C</caption>

were observed. A similar result was obtained for the reaction with 1-phenylpyrrole. Reactions performed at a higher temperature with thiophene-2-carbonitrile, 2-chlorothiophene afforded **3** and **4** in slightly lower yields. Gorelsky calculated that the Gibbs free energies of activation for the cleavage of C–H bonds

at C5-position of thiophene or pyrrole derivatives, for reaction which proceed via concerted metallation–deprotonation [38–40], are higher than that of thiazoles (see bottom of Scheme 2) [42]. We assume that, due to these higher energies of activation for reactions with thiophene or pyrrole, larger amounts of selenophene oligomers were formed in the presence of these less reactive heteroarenes. Then, the reactivity of imidazo[1,2-a]pyridine, which contains a very reactive C–H bond at C3-position was examined. The expected product **7** was obtained in a high yield of 81%. Thus, for Pd-catalyzed direct heteroarylations of 2-bromoselenophene, only the heteroarenes containing C–H bonds with low Gibbs free energies of activation [41] should be employed.

By contrast, the direct arylation reactions with 2,5-dibromoselenophene were found to tolerate both thiazole and thiophene derivatives (Scheme 3). The coupling of 3 equiv of thiazole derivatives with 2,5-dibromoselenophene in the presence of 2 mol % Pd(OAc)₂ and KOAc as base gave the corresponding 2,5-diheteroarylated selenophenes **8** and **9** in 78% and 80% yields, respectively. The use of 2-pentyl- and 2-chlorothiophenes also gave the desired products **10** and **11** in high yields. In general, the Pd-catalyzed direct arylation of 3-substituted thiophenes with aryl halides afforded quite regioselectively the C2-arylated thiophenes [30]. A similar regioselectivity was observed for the coupling of thiophene derivatives containing methyl- or chloro-substituents at the C3-position with 2,5-dibromoselenophene. In both cases, regioselective arylations at the C2-positions were observed, affording the 2,5-diarylated selenophenes **12** and **13** in 69% and 72% yields, respectively. From 2,5-dibromoselenophene and an excess of 1-methylpyrrole, the expected 2,5-diarylated selenophene **14** was obtained in 81% yield.

<figure><img src="image_7.png" /><figcaption>**Scheme 3:** Palladium-catalyzed 2,5-diheteroarylation of 2,5-dibromoselenophene.</figcaption></figure>

<figure><img src="image_8.png" /></figure>
Finally, we show a sequential transformation leading to 2-aryl-5-(heteroaryl)selenophenes in three steps from commercially available compounds (Scheme 4). Bromination at the C5-position of 2-arylselenophenes containing nitrile, acetyl or chloro substituents on the aryl moiety, which could be easily obtained in good yields from selenophene and aryl bromides via a Pd-catalyzed direct arylation using a reported procedure [33], afforded the 2-aryl-5-bromoselenophenes **15–17** in 84–90% yields. Then, a second Pd-catalyzed direct arylation using heteroarenes and **15–17** as reaction partners, provided the target compounds **18–26** in high yields. Both thiazole and thiophene derivatives were successfully employed in this transformation. The reaction tolerates useful functional groups on both coupling partners such as nitrile, acetyl or chloro. It should be mentioned that again a regioselective arylation at the C2-position of 3-chlorothiophene was observed affording **26** in 72% yield.

Although the mechanism of these reactions was not elucidated, the catalytic cycle shown on Scheme 5 can be proposed. The first step is probably the oxidative addition of the 2-bromoselenophene to Pd(0) to afford the Pd(II) intermediate **A**. Then, after elimination of KBr with KOAc, a concerted metala tion–deprotonation pathway involving an heteroarene gives **B**. Reductive elimination affords the 2-heteroarylated selenophene with regeneration of the Pd(0) species.

Conclusion

In summary, the reactivity of 2-bromoselenophenes was investi gated and revealed that the C2-heteroarylation of 2-bromo- selenophene in high yields is only possible with specific heteroarenes such as thiazoles and imidazopyridines, whereas thiophene or pyrroles gave the desired products in low yields. Conversely, 2,5-dibromoselenophene was successfully coupled with both thiazoles and thiophenes in the presence of phos phine-free Pd(OAc)₂ catalyst precursor and KOAc as inexpen sive base, affording the desired 2,5-diheteroarylated seleno- phenes in high yields. We also described that the sequential cat alytic C2-arylation, bromination, and catalytic C5-arylation of selenophene provides the controled double (hetero)arylation at the C2 and C5 positions of selenophene in good yields.

Experimental

General procedure for palladium-catalyzed
direct mono-heteroarylations of 2-bromo-
selenophene

The reaction of the heteroarene (1.5 mmol), 2-bromoseleno-
phene (0.210 g, 1 mmol) and KOAc (0.196 g, 2 mmol) at 90 °C
during 24 h in DMA (4 mL) in the presence of Pd(OAc)₂
(4.5 mg, 0.02 mmol), under argon affords the coupling
products **1–7** after evaporation of the solvent and purification
on silica gel. Eluents: Pentane for compounds **3** and **4**.

<figure><img src="image_9.png" /><figcaption>**Scheme 4:** Synthesis of 2-aryl-5-(heteroaryl)selenophenes.</figcaption></figure>
<figure><img src="image_10.png" /><figcaption>**Scheme 5:** Proposed catalytic cycle.</figcaption></figure>

EtOAc/pentane 2:98 for compounds **1** and **6**. EtOAc/pentane 10:90 for compound **2** and **5** and EtOAc/pentane 40:60 for compound **7**.

## General procedure for palladium-catalyzed direct diheteroarylations

The reaction of the heteroarene (3 mmol), 2,5-dibromoselenophene (0.289 g, 1 mmol) and KOAc (0.392 g, 4 mmol) at 90 °C during 40 h in DMA (4 mL) in the presence of Pd(OAc)₂ (4.5 mg, 0.02 mmol), under argon affords the coupling products **8–14** after evaporation of the solvent and purification on silica gel. Eluents: Pentane for compounds **10–13**. EtOAc/pentane 5:95 for compounds **8**, **9** and **14**.

## General procedure for the synthesis of 5-bromo-2-arylselenophenes **15–17**

To a mixture of the 2-arylselenophene [2] (2 mmol) in DMF (5 mL) at 0 °C, N-bromosuccinimide (0.392 g, 2.2 mmol) was slowly added. Then, the mixture was allowed to increase to room temperature and stirred during 20 h. After addition of water, the extraction was carried out with diethyl ether. Then, the organic phase was dried over magnesium sulphate. Finally, evaporation of the solvent and purification on silica gel afforded the 5-bromo-2-arylselenophenes **15–17**. Eluents: Pentane for compounds **15** and **16**. EtOAc:pentane 5:95 for compound **17**.

## General procedure for palladium-catalyzed direct mono-heteroarylations of 2-bromo-5-arylselenophenes

The reaction of the heteroarene (1.2 mmol), 2-bromo-5-arylselenophene **15–17** (1 mmol) and KOAc (0.392 g, 4 mmol) at 150 °C during 16 h in DMA (4 mL) in the presence of Pd(OAc)₂ (4.5 mg, 0.02 mmol), under argon affords the coupling products **18–26** after evaporation of the solvent and purification on silica gel. Eluents: Pentane for compounds **21** and **22**. EtOAc/pentane 5:95 for compounds **18** and **19**. EtOAc/pentane 10:90 for compounds **20**, **23**, **24** and **26**. EtOAc/pentane 20:80 for compound **25**.

## Supporting Information

### Supporting Information File 1

Additional experimental and analytical data and copies of NMR spectra.

[http://www.beilstein-journals.org/bjoc/content/supplementary/1860-5397-13-278-S1.pdf]

## Acknowledgements

We are grateful the CNRS, Rennes Metropole and Scientific Ministry of Higher Education and Research of Tunisia for providing financial support.
ORCID® iDs

Ridha Ben Salem - https://orcid.org/0000-0002-5179-351X

Jean-François Soulé - https://orcid.org/0000-0002-6593-1995

Henri Doucet - https://orcid.org/0000-0002-1410-3663

References

1. Hollinger, J.; Jahnke, A. A.; Coombs, N.; Seferos, D. S. *J. Am. Chem. Soc.* **2010**, *132*, 8546–8547. doi:10.1021/ja103191u

2. Yen, Y.-S.; Lee, C.-T.; Hsu, C.-Y.; Chou, H.-H.; Chen, Y.-C.; Lin, J. T. *Chem. – Asian J.* **2013**, *8*, 809–816. doi:10.1002/asia.201201173

3. Liu, Y.; Yang, Y.; Chen, C.-C.; Chen, Q.; Dou, L.; Hong, Z.; Li, G.; Yang, Y. *Adv. Mater.* **2013**, *25*, 4657–4662. doi:10.1002/adma.201301716

4. Li, R.; Lv, X.; Shi, D.; Zhou, D.; Cheng, Y.; Zhang, G.; Wang, P. *J. Phys. Chem. C* **2009**, *113*, 7469–7479. doi:10.1021/jp900972v

5. Haid, S.; Mishra, A.; Weil, M.; Uhrich, C.; Pfeiffer, M.; Bäuerle, P. *Adv. Funct. Mater.* **2012**, *22*, 4322–4333. doi:10.1002/adfm.201201018

6. Khim, D.; Lee, W.-H.; Baeg, K.-J.; Kim, D.-Y.; Kang, I.-N.; Noh, Y.-Y. *J. Mater. Chem.* **2012**, *22*, 12774–12783. doi:10.1039/c2jm16546e

7. Lee, W.-H.; Son, S. K.; Kim, K.; Lee, S. K.; Shin, W. S.; Moon, S.-J.; Kang, I.-N. *Macromolecules* **2012**, *45*, 1303–1312. doi:10.1021/ma2020112

8. Lee, W.-H.; Lee, S. K.; Son, S. K.; Choi, J.-E.; Shin, W. S.; Kim, K.; Lee, S.-H.; Moon, S.-J.; Kang, I.-N. *J. Polym. Sci, Part A: Polym. Chem.* **2012**, *50*, 551–561. doi:10.1002/pola.25064

9. Agrawal, V.; Shahjad, Bhardwaj, D.; Bhargav, R.; Sharma, G. D.; Bhardwaj, R. K.; Patra, A.; Chand, S. *Electrochim. Acta* **2016**, *192*, 52–60. doi:10.1016/j.electacta.2016.01.157

10. Shabana, R.; Galal, A.; Mark, H. B., Jr.; Zimmer, H.; Gronowitz, S.; Hörnfeldt, A.-B. *Phosphorus, Sulfur Silicon Relat. Elem.* **1990**, *48*, 239–244. doi:10.1080/10426509008045904

11. Prediger, P.; Moro, A. V.; Nogueira, C. W.; Savegnago, L.; Menezes, P. H.; Rocha, J. B. T.; Zeni, G. *J. Org. Chem.* **2006**, *71*, 3786–3792. doi:10.1021/jo0601056

12. Kong, H.; Jung, Y. K.; Cho, N. S.; Kang, I.-N.; Park, J.-H.; Cho, S.; Shim, H.-K. *Chem. Mater.* **2009**, *21*, 2650–2660. doi:10.1021/cm803409q

13. Kong, H.; Chung, D. S.; Kang, I.-N.; Park, J.-H.; Park, M.-J.; Jung, I. H.; Park, C. E.; Shim, H.-K. *J. Mater. Chem.* **2009**, *19*, 3490–3499. doi:10.1039/b823082j

14. Mishra, S. P.; Javier, A. E.; Zhang, R.; Liu, J.; Belot, J. A.; Osaka, I.; McCullough, R. D. *J. Mater. Chem.* **2011**, *21*, 1551–1561. doi:10.1039/C0JM00602E

15. Haid, S.; Mishra, A.; Uhrich, C.; Pfeiffer, M.; Bäuerle, P. *Chem. Mater.* **2011**, *23*, 4435–4444. doi:10.1021/cm201392c

16. Klingstedt, T.; Shirani, H.; Aslund, K. O. A.; Cairns, N. J.; Sigurdson, C. J.; Goedert, M.; Nilsson, K. P. *R. Chem. – Eur. J.* **2013**, *19*, 10179–10192. doi:10.1002/chem.201301463

17. Salamoun, J.; Anderson, S.; Burnett, J. C.; Gussio, R.; Wipf, P. *Org. Lett.* **2014**, *16*, 2034–2037. doi:10.1021/ol500620m

18. Shirani, H.; Linares, M.; Sigurdson, C. J.; Lindgren, M.; Norman, P.; Nilsson, K. P. *R. Chem. – Eur. J.* **2015**, *21*, 15133–15137. doi:10.1002/chem.201502999

19. Ho, P.-Y.; Siu, C.-H.; Yu, W.-H.; Zhou, P.; Chen, T.; Ho, C.-L.; Lee, L. T. L.; Feng, Y.-H.; Liu, J.; Han, K.; Lo, Y. H.; Wong, W.-Y. *J. Mater. Chem. C* **2016**, *4*, 713–726. doi:10.1039/C5TC03308J

20. Shabana, R.; Galal, A.; Mark, H. B., Jr.; Zimmer, H.; Gronowitz, S.; Hörnfeldt, A. B. *J. Chem. Soc., Chem. Commun.* **1988**, 988–989. doi:10.1039/C39880000988

See for the synthesis of heteroarylated selenophenes via Kumada coupling.

21. Skhiri, A.; Ben Salem, R.; Soulé, J.-F.; Doucet, H. *ChemCatChem* **2017**, *9*, 2895–2913. doi:10.1002/cctc.201700256
See for a review on the arylation of selenophenes via Pd-catalyzed reactions.

22. Akita, Y.; Inoue, A.; Yamamoto, K.; Ohta, A.; Kurihara, T.; Shimizu, M. *Heterocycles* **1985**, *23*, 2327–2333. doi:10.3987/R-1985-09-2327

23. Alberico, D.; Scott, M. E.; Lautens, M. *Chem. Rev.* **2007**, *107*, 174–238. doi:10.1021/cr0509760

24. Satoh, T.; Miura, M. *Chem. Lett.* **2007**, *36*, 200–205. doi:10.1246/cl.2007.200

25. Li, B.-J.; Yang, S.-D.; Shi, Z.-J. *Synlett* **2008**, 949–957. doi:10.1055/s-2008-1042907

26. Ackermann, L. *Chem. Rev.* **2011**, *111*, 1315–1345. doi:10.1021/cr100412j

27. Wencel-Delord, J.; Glorius, F. *Nat. Chem.* **2013**, *5*, 369–375. doi:10.1038/nchem.1607

28. Rossi, R.; Bellina, F.; Lessi, M.; Manzini, C. *Adv. Synth. Catal.* **2014**, *356*, 17–117. doi:10.1002/adsc.201300922

29. Yuan, K.; Soulé, J.-F.; Doucet, H. *ACS Catal.* **2015**, *5*, 978–991. doi:10.1021/cs501686d

30. Bheeter, C. B.; Chen, L.; Soulé, J.-F.; Doucet, H. *Catal. Sci. Technol.* **2016**, *6*, 2005–2049. doi:10.1039/C5CY02095F

31. Rossi, R.; Lessi, M.; Manzini, C.; Marianetti, G.; Bellina, F. *Tetrahedron* **2016**, *72*, 1795–1837. doi:10.1016/j.tet.2016.02.037

32. Tamba, S.; Fujii, R.; Mori, A.; Hara, K.; Koumura, N. *Chem. Lett.* **2011**, *40*, 922–924. doi:10.1246/cl.2011.922

33. Rampon, D. S.; Wessjohann, L. A.; Schneider, P. H. *J. Org. Chem.* **2014**, *79*, 5987–5992. doi:10.1021/jo500094t

34. Lu, T.-J.; Lin, P.-H.; Lee, K.-M.; Liu, C.-Y. *Eur. J. Org. Chem.* **2017**, 111–123. doi:10.1002/ejoc.201601257

35. Skhiri, A.; Ben Salem, R.; Soulé, J.-F.; Doucet, H. *Chem. – Eur. J.* **2017**, *23*, 2788–2791. doi:10.1002/chem.201700202

36. Roger, J.; Doucet, H. *Tetrahedron* **2009**, *65*, 9772–9781. doi:10.1016/j.tet.2009.09.084

37. Gronowitz, S.; Peters, D. *Heterocycles* **1990**, *30*, 645–658. doi:10.3987/COM-89-S90

38. Davies, D. L.; Donald, S. M. A.; Macgregor, S. A. *J. Am. Chem. Soc.* **2005**, *127*, 13754–13755. doi:10.1021/ja052047w

39. Lafance, M.; Fagnou, K. *J. Am. Chem. Soc.* **2006**, *128*, 16496–16497. doi:10.1021/ja067144j

40. Lapointe, D.; Fagnou, K. *Chem. Lett.* **2010**, *39*, 1118–1126. doi:10.1246/cl.2010.1118

41. Gorelsky, S. I. *Coord. Chem. Rev.* **2013**, *257*, 153–164. doi:10.1016/j.ccr.2012.06.016

42. Zimmer, H.; Shabana, R.; Galal, A.; Mark, H. B., Jr.; Gronowitz, S.; Hörnfeldt, A. B. *Phosphorus, Sulfur Silicon Relat. Elem.* **1989**, *42*, 171–176. doi:10.1080/10426508908054892
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