University of Groningen Gold(I) Catalysis Taschinski, Svenja

(1)

Gold(I) Catalysis

Taschinski, Svenja

DOI:

10.33612/diss.126022756

IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from

it. Please check the document version below.

Document Version

Publisher's PDF, also known as Version of record

Publication date:

2020

Link to publication in University of Groningen/UMCG research database

Citation for published version (APA):

Taschinski, S. (2020). Gold(I) Catalysis: Mechanistic Insights, Reactivity of Intermediates and its

Applications. University of Groningen. https://doi.org/10.33612/diss.126022756

Copyright

Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).

Take-down policy

If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum.

(2)

Chapter 1 Introduction

Abstract: In this chapter, a general introduction to gold catalysis, the synthesis of catalysts and vinyl gold(I) complexes as key intermediates are provided.

While many reactions involve intermediates that can hardly be synthesized, vinyl gold(I) complexes have been discovered as isolatable complexes a few years ago. Although some of them are air-stable and easy to isolate, only a few studies on their reactivity are published. Some recent examples are discussed as probes for the elucidation of possible pathways to deaurate vinyl gold(I) complexes with electrophiles, an elementary step that can proceed intra- or intermolecularly.

(3)

20

1.1)

Catalysis Involving Vinyl Gold(I) Complexes

Gold catalysis developed to a prominent research topic over the last decades.[1]_{One of the}

key reactions in the field of gold-catalyzed chemistry has been reported 1976 by Thomas and co-workers.[2]_{Without knowing that this might be one of the first published gold-catalyzed}

reactions that opens up a new research area, the authors reported a Markovnikov addition that transforms alkynes 1 into related ketones 2 as major products catalyzed by tetrachloroauric acid.[2]_{The mechanism was proposed to be a gold(III) oxidation similar to the}

known oxidation by mercury(II)[2]_{although the reaction reached almost six turnovers.}[1b]

Scheme 1: First experiments reported for the gold-catalyzed reaction of alkynes 1 to ketones 2, 3,

methyl vinyl ethers 4 and vinyl chlorides 5 by Thomas and co-workers.[2]

Despite some work reporting gold(III) in catalysis, for example reports by Hutchings (hydrochlorination of alkynes)[3]_{and Utimoto (hydration of propargyl ethers),}[4]_{gold seemed to}

be “catalytically dead” and known as a non-reactive noble metal.[5]

At the same time, the structural characterization of a L-Au(I) complex, which later on became one of the most used precursors for cationic complexes and catalytic reactions,[1b]_{has been}

reported by Soboroff and co-workers in 1976.[6]_{The group synthesized Ph}

3PAuCl 7Ph3P,Cl by

treating Ph3P 6 with tetrachloroauric acid (see Scheme 2) and characterized it by

single-crystal X-ray structure analysis.

Scheme 2: Left: Synthesis of Ph3PAuCl 7Ph3P,Cl reported by Soboroff and co-workers.[7] Right:

Single-crystal X-ray structure of Ph3PAuCl 7Ph3P,Cl (hydrogen atoms omitted for clarity; picture

The catalytic relevance of such cationic phosphine complexes has been demonstrated in 1986 by Ito and co-workers[8]_{and by Teles and co-workers in 1998.}[9]_{For the first time, gold(I)}

complexes were used for the conversion of alkynes,[9]_{namely a gold-catalyzed addition of}

methanol to propyne 8Me (see Scheme 3). With turnover frequencies up to 1500 depending

on the electronic nature of the ligand, this is the first study on ligand-depending reactivity reported.[9]_{The group explored that electron-poor ligands increase the activity of}

(4)

21

Introduction

Scheme 3: Selected turnover frequencies for the gold-catalyzed addition of methanol to

propyne 8Me reported by Teles and co-workers.[9]

Only two years later, the power of gold(I) in catalytic reactions has been demonstrated by Hashmi and co-workers.[10]_{A comprehensive study showed how useful gold catalysis can be}

compared with known reactivities of other transition metal catalysts, such as Ag(I) and Pd(II).[10]_{When treating the same starting materials with gold(III) complexes, reaction times}

could be decreased by the choice of catalyst from a week (AgNO3), over one hour

(PdCl2(MeCN)2) to one minute (AuCl3). Despite the shortening in reaction times, gold was able

to catalyze the transformation of propargylketones, such as 10, to furans 11 at room temperature (see Scheme 4).[10]_{This reaction could not be catalyzed by Ag(I)}[10]_{and required}

temperatures of 70-100°C when using a Pd(II)-catalyst.[11]

Scheme 4: Gold(III)-catalyzed C-O-bond formation reported by Hashmi and co-workers.[10] Gold(III) catalysis was subsequently studied in detail due to its “special” reactivity allowing for mild conditions and the reactions reported earlier were re-explored. A number of different catalytic reactions were reported and the field of gold catalysis grew enormously[1] _{as well as}

the design of air-stable (pre-)catalysts,[9, 12]_{with phosphine-gold(I) or NHC-gold(I) catalysts}

being used most commonly.

The first isolated NHC-gold(I) complexes were reported in 1989 by Bovio and co-workers by transmetallating lithium imidazoles with Ph3PAuCl / Me2SAuCl at low temperatures

(-40°C).[12c]_{Their usage in catalytic reactions was first reported in 1998 by Teles and}

co-workers and 2003 by Herrmann and co-workers.[9, 13]_{A series of air-stable NHC-gold(I)}

complexes was introduced by Nolan and co-workers,[12a, 12b]_{who isolated and characterized}

Au-chlorides and their cationic analogues by transmetallation of Ag(I) complexes or through direct coupling of imidazol-2-ylidene carbenes with Me2SAuCl at room temperature (see

(5)

22

Figure 1: Structures (left) and single-crystal X-ray structures (right) of IPrAuCl 12IPr and

IMesAuCl 13IMes (hydrogen atoms omitted for clarity; picture reprinted with permission from P. de

These types of complexes have a linear (180°, 13IMes) and almost linear (177°, 12IPr) geometry

at the C-Au-Cl angle and Au-C(NHC) distances of 13IMes = 1.998(5) Å and

12IPr = 1.979(3) Å.[12b] The values are comparable with the bond angle reported for

Ph3PAuCl 7Ph3P,Cl (P-Au-Cl = 179.68(8) Å), but the Au-P distance is longer (2.235(3) Å).[6]

Both complex chlorides can easily be transformed into their cationic analogues by ligand exchange with silver(I) salts.[9, 12a, 12b]_{With the possibility to generate the active, cationic}

complexes either in situ or isolate them first and subsequently add them to the reaction mixture, gold-catalyzed reactions are easy to apply and the influence of ligand or counter anion as well as solvent were studied systematically over time.[1a-d, 7, 14]_{A few theoretical}[14f, 15]

and experimental studies[14a, 14e, 14f, 16]_{explore how isolated}[16]_{or in situ-generated}[17]_gold(I)

complexes can be influenced by the electronic nature of the substituents, the choice of ligand or reaction conditions.

To date, gold(I) and gold(III) catalytic cycles to functionalize C-C-multiple bonds can be generally described by the coordination of the prior or in situ-activated catalyst to the -bond of the molecule as the start of the catalytic cycle. The Lewis-acidic gold catalyst 14 activates the multiple bond towards an inter- / intramolecular nucleophilic attack to form gold(I)/(III) intermediate 16.[18]_{Electrophilic inter- / intramolecular deauration closes the catalytic cycle}

and releases the active catalyst.[19]

Scheme 5: Prototypical catalytic cycle of gold-catalyzed reactions involving gold(I/III)

(6)

23

Introduction

To support the catalytic involvement of gold(I) in triple-bond conversions and to gain deeper understanding of its mechanism, well-characterized, air-stable vinyl gold(I) complexes were isolated by several groups[14a, 14f, 20]_{(see Scheme 6)}_{with a coordination geometry that}

remains almost linear and Au-C(NHC) / Au-P-distances[20e-i]_{comparable to the related}

gold(I) chlorides.[6, 12b]

Scheme 6: Selected examples for isolated vinyl gold(I) complexes 18-21 and their single-crystal

X-ray structures (hydrogens are omitted for clarity, except top right; pictures reprinted with permission from J. A. Akana, K. X. Bhattacharyya, P. Müller, J. P. Sadighi, J. Am. Chem. Soc. 2007,

G. B. Hammond, J. Am. Chem. Soc. 2008, 130, 17642-17643. Copyright © 2008, American Chemical Society; A. S. K. Hashmi, A. M. Schuster, F. Rominger, Angew. Chem. 2009, 121, 8396-8398; Angew. Chem. Int. Ed. 2009, 48, 8247-8249. Copyright © 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim and D. Weber, M. A. Tarselli, M. R. Gagné, Angew. Chem. Int. Ed. 2009,

48, 5733-5736. Copyright © 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim).[20e-i] The bigger the field grew, the more attention gold(I)-catalyzed reactions involving electrophilic deauration for C-C-bond or C-X-bond formation received. The majority of gold-catalyzed reactions are reported with a proton as electrophile that terminates the catalytic cycle.[14e]

Some approaches reported catalytic reactions that trap intermediates with different groups, such as carbon-,[20a, 21]_silicon-,[22]_{trifluoromethyl-,}[23]_halogen-,[20i, 24]_tin-,[25]_{or sulfonyl-}[26]

electrophiles, as well as some stoichiometric reactions involving gold complexes as intermediates, such as gold-alkynyl,[27]_-vinyl,[24c]_-allenyl,[20e]_-aryl[24c, 28]_{and -alkyl}[29]

complexes, respectively. Focussing on vinyl gold intermediates, there are three possible ways to deaurate a vinyl gold complex by an electrophile: (i) intermolecular with oxidative addition and reductive elimination; (ii) intramolecular by sigmatropic rearrangement and

(iii) intermolecular by external substitution (see Scheme 7). The strategies will be elucidated

(7)

24

Scheme 7: Possible strategies for electrophilic deauration of vinyl gold intermediates.

In the intermolecular strategy with an external electrophile and a metal redox-activation (see Scheme 7, left), the electrophile is oxidatively added to the (pre)catalyst or intermediate and reductive elimination results in C-R-bond formation. With this method, alkynylative arylation with iodoalkynes and [Ir(dF(CF3)ppy)2(dtbbpy)]PF6 as photo(redox) catalyst to substituted

benzofurans 26 was recently reported by Fensterbank and co-workers (see Scheme 8).[20a]

(8)

25

Introduction

The group proposes the formation of a vinyl gold(I) intermediate, that is oxidized by the Ir co-catalyst to a gold(III) intermediate and subsequent reductive elimination closes the catalytic cycle. Here, it shall be noted that stoichiometric attempts without the Ir co-catalyst gave the desired product in low to moderate yields and that the co-catalyst might only promote the excited state of the vinyl gold(I) intermediate and enhances the formation of 27.[20a]

As another selected example representing this strategy, the C-F-bond formation through a fluorination / hydration mechanism with selectfluor as oxidant to -fluorobenzofuranones 29 was reported by Shi and co-workers.[30]_{The vinyl gold(I) complex is oxidized by selectfluor to}

a vinyl gold(III) intermediate, that releases the fluorinated product 29 under reductive elimination and subsequent hydration (see Scheme 9).[30]

Scheme 9: C-F-bond formation through a gold(I/III) fluorination / hydration mechanism.[30]

The intramolecular sigmatropic rearrangement (see Scheme 7, middle) proceeds through a cationic vinyl gold(I) intermediate C, that is subsequently deaurated by the shifting group to form the substituted product 24. A structural analogue example to benzofurans for sigmatropic rearrangement was reported by Nakamura and co-workers, that used gold(I) catalysis to synthesize substituted benzothiophenes 31 starting form o-alkynylsulfides 30, respectively (see Scheme 10).[21c, 22b]

Scheme 10: Gold(I)-catalyzed sigmatropic rearrangement to substituted benzothiophenes 31 by

(9)

26

For the last strategy shown in Scheme 7 (right), an external electrophile deaurates the priorly formed vinyl gold(I) intermediate D to substituted benzofuran 24 and no change in oxidation state at the gold center is taking place. A selected example was given by Ackermann[31]_and

Döpp[32]_{in our group. The formation of substituted azobenzofurans 32 by external electrophilic}

deauration of vinyl gold(I) complex 46OMe,IPr with diazonium salt 34OMe was demonstrated (see

Scheme 11).

Scheme 11: Stoichiometric experiments for the formation of azobenzofuran 32OMe,OMe.[31]

The following thesis will give a deeper understanding in the deauration of vinyl gold(I) intermediates with external electrophiles and how the substitution pattern of both as well as the reaction conditions influence the reactivity.

(10)

27

References

1.2)

References

[1] a) A. Arcadi, Chem. Rev. 2008, 108, 3266-3325; b) A. S. K. Hashmi, Chem. Rev. 2007, 107, 3180-3211; c) A. S. K. Hashmi, G. J. Hutchings, Angew. Chem. 2006, 118, 8064-8105; d) A. S. K. Hashmi, G. J. Hutchings, Angew. Chem. Int. Ed. 2006, 45, 7896-7936; e) A. S. K. Hashmi,

Angew. Chem. Int. Ed. 2005, 44, 6990-6993; f) A. S. K. Hashmi, Angew. Chem. 2005, 117,

7150-7154; g) A. M. Echavarren, C. Nevado, Chem. Soc. Rev. 2004, 33, 431-436; h) A. S. K. Hashmi, Gold Bulletin 2003, 36, 3-9; i) G. Dyker, Angew. Chem. Int. Ed. 2000, 39, 4237-4239; j) G. Dyker, Angew. Chem. 2000, 112, 4407-4409.

[2] R. O. C. Norman, W. J. E. Parr, C. B. Thomas, J. Chem. Soc., Perkin Trans. 1 1976, 1983-1987.

[3] G. J. Hutchings, J. Catal. 1985, 96, 292-295.

[4] a) Y. Fukuda, K. Utimoto, J. Org. Chem. 1991, 56, 3729-3731; b) Y. Fukuda, K. Utimoto,

Synthesis 1991, 1991, 975-978; c) F. Yukitoshi, U. Kiitiro, Bull. Chem. Soc. Jpn. 1991, 64,

2013-2015.

[5] H. Schmidbaur, Naturwiss. Rundsch. 1995, 48, 443.

[6] N. C. Baenziger, W. E. Bennett, D. M. Soborofe, Acta Cryst. Section B 1976, 32, 962-963. [7] a) A. Fürstner, P. W. Davies, Angew. Chem. 2007, 119, 3478-3519; b) A. Fürstner, P. W.

Davies, Angew. Chem. Int. Ed. 2007, 46, 3410-3449.

[8] Y. Ito, M. Sawamura, T. Hayashi, J. Am. Chem. Soc. 1986, 108, 6405-6406.

[9] a) J. H. Teles, S. Brode, M. Chabanas, Angew. Chem. 1998, 110, 1475-1478; b) J. H. Teles, S. Brode, M. Chabanas, Angew. Chem. Int. Ed. 1998, 37, 1415-1418; c) J. H. S. Teles, M. (BASF AG), WO-A19721648,1997, Chem. Abstr. 1997, 127, 121499.

[10] a) A. S. K. Hashmi, L. Schwarz, J.-H. Choi, T. M. Frost, Angew. Chem. Int. Ed. 2000, 39, 2285-2288; b) A. S. K. Hashmi, L. Schwarz, J.-H. Choi, T. M. Frost, Angew. Chem. 2000, 112, 2382-2385.

[11] H. Sheng, S. Lin, Y. Huang, Synthesis 1987, 1987, 1022-1023.

[12] a) P. de Frémont, E. D. Stevens, M. R. Fructos, M. Mar Díaz-Requejo, P. J. Pérez, S. P. Nolan,

Chem. Commun. 2006, 2045-2047; b) P. de Frémont, N. M. Scott, E. D. Stevens, S. P. Nolan, Organometallics 2005, 24, 2411-2418; c) F. Bonati, A. Burini, B. R. Pietroni, B. Bovio, J. Organomet. Chem. 1989, 375, 147-160.

[13] S. K. Schneider, W. A. Herrmann, E. Herdtweck, Z. anorg. allg. Chem. 2003, 629, 2363-2370. [14] a) Z. Lu, G. B. Hammond, B. Xu, Acc. Chem. Res. 2019, 52, 1275-1288; b) J. Schießl, P. M. Stein, J. Stirn, K. Emler, M. Rudolph, F. Rominger, A. S. K. Hashmi, Adv. Synth. Catal. 2019,

361, 725-738; c) J. Schießl, J. Schulmeister, A. Doppiu, E. Wörner, M. Rudolph, R. Karch, A.

S. K. Hashmi, Adv. Synth. Catal. 2018, 360, 3949-3959; d) J. Schießl, J. Schulmeister, A. Doppiu, E. Wörner, M. Rudolph, R. Karch, A. S. K. Hashmi, Adv. Synth. Catal. 2018, 360, 2493-2502; e) W. Wang, G. B. Hammond, B. Xu, J. Am. Chem. Soc. 2012, 134, 5697-5705; f) R. Döpp, C. Lothschütz, T. Wurm, M. Pernpointner, S. Keller, F. Rominger, A. S. K. Hashmi,

Organometallics 2011, 30, 5894-5903; g) M. Rudolph, A. S. K. Hashmi, Chem. Commun. 2011, 47, 6536-6544; h) A. S. K. Hashmi, M. Buehrle, Aldrichim. Acta 2010, 43, 27-33; i) Z. Li, C.

Brouwer, C. He, Chem. Rev. 2008, 108, 3239-3265.

[15] a) L. Nunes dos Santos Comprido, J. E. M. N. Klein, G. Knizia, J. Kästner, A. S. K. Hashmi,

Chem. Eur. J. 2017, 23, 10901-10905; b) C. A. Gaggioli, G. Ciancaleoni, D. Zuccaccia, G.

Bistoni, L. Belpassi, F. Tarantelli, P. Belanzoni, Organometallics 2016, 35, 2275-2285; c) R. BabaAhmadi, P. Ghanbari, N. A. Rajabi, A. S. K. Hashmi, B. F. Yates, A. Ariafard,

Organometallics 2015, 34, 3186-3195.

[16] K. E. Roth, S. A. Blum, Organometallics 2010, 29, 1712-1716. [17] A. Zhdanko, M. E. Maier, Chem. Eur. J. 2014, 20, 1918-1930.

[18] M. Pernpointner, A. S. K. Hashmi, J. Chem. Theory Comput. 2009, 5, 2717-2725.

[19] a) A. S. K. Hashmi, Angew. Chem. Int. Ed. 2010, 49, 5232-5241; b) A. S. K. Hashmi, Angew.

Chem. 2010, 5360 – 5369.

[20] a) Z. Xia, V. Corcé, F. Zhao, C. Przybylski, A. Espagne, L. Jullien, T. Le Saux, Y. Gimbert, H. Dossmann, V. Mouriès-Mansuy, C. Ollivier, L. Fensterbank, Nat. Chem. 2019; b) L. Biasiolo, L. Belpassi, C. A. Gaggioli, A. Macchioni, F. Tarantelli, G. Ciancaleoni, D. Zuccaccia,

(11)

28

Synth. Catal. 2010, 352, 971-975; d) Y. Chen, D. Wang, J. L. Petersen, N. G. Akhmedov, X.

Shi, Chem. Commun. 2010, 46, 6147-6149; e) D. Weber, M. A. Tarselli, M. R. Gagné, Angew.

Chem. Int. Ed. 2009, 48, 5733-5736; f) A. S. K. Hashmi, A. M. Schuster, F. Rominger, Angew. Chem. 2009, 121, 8396-8398; g) A. S. K. Hashmi, A. M. Schuster, F. Rominger, Angew. Chem. Int. Ed. 2009, 48, 8247-8249; h) L.-P. Liu, B. Xu, M. S. Mashuta, G. B. Hammond, J. Am. Chem. Soc. 2008, 130, 17642-17643; i) J. A. Akana, K. X. Bhattacharyya, P. Müller, J. P. Sadighi, J. Am. Chem. Soc. 2007, 129, 7736-7737.

[21] a) M. Ackermann, J. Bucher, M. Rappold, K. Graf, F. Rominger, A. S. K. Hashmi, Chem. Asian

J. 2013, 8, 1786-1794; b) P. Dubé, F. D. Toste, J. Am. Chem. Soc. 2006, 128, 12062; c) I.

Nakamura, T. Sato, Y. Yamamoto, Angew. Chem. Int. Ed. 2006, 45, 4473-4475; d) L. Zhang,

J. Am. Chem. Soc. 2005, 127, 16804-16805.

[22] a) P. McGee, G. Bellavance, I. Korobkov, A. Tarasewicz, L. Barriault, Chem. Eur. J. 2015, 21, 9662-9665; b) I. Nakamura, T. Sato, M. Terada, Y. Yamamoto, Org. Lett. 2007, 9, 4081-4083. [23] A. Boreux, G. H. Lonca, O. Riant, F. Gagosz, Org. Lett. 2016, 18, 5162-5165.

[24] a) D. H. Miles, M. Veguillas, F. D. Toste, Chem. Sci. 2013, 4, 3427-3431; b) A. S. K. Hashmi, T. D. Ramamurthi, M. H. Todd, A. S.-K. Tsang, K. Graf, Aust. J. Chem. 2010, 63, 1619-1626; c) A. Stephen K. Hashmi, T. Dondeti Ramamurthi, F. Rominger, J. Organomet. Chem. 2009,

694, 592-597.

[25] Y. Shi, S. D. Ramgren, S. A. Blum, Organometallics 2009, 28, 1275-1277.

[26] I. Nakamura, U. Yamagishi, D. Song, S. Konta, Y. Yamamoto, Angew. Chem. Int. Ed. 2007, 46, 2284-2287.

[27] a) R. Cai, M. Lu, E. Y. Aguilera, Y. Xi, N. G. Akhmedov, J. L. Petersen, H. Chen, X. Shi, Angew.

Chem. Int. Ed. 2015, 54, 8772-8776; b) A. S. K. Hashmi, I. Braun, M. Rudolph, F. Rominger, Organometallics 2012, 31, 644-661; c) K. J. Kilpin, R. Horvath, G. B. Jameson, S. G. Telfer, K.

C. Gordon, J. D. Crowley, Organometallics 2010, 29, 6186-6195.

[28] M. T. Johnson, J. Marthinus Janse van Rensburg, M. Axelsson, M. S. G. Ahlquist, O. F. Wendt,

Chem. Sci. 2011, 2, 2373-2377.

[29] R. L. LaLonde, J. W. E. Brenzovich, D. Benitez, E. Tkatchouk, K. Kelley, I. I. I. W. A. Goddard, F. D. Toste, Chem. Sci. 2010, 1, 226-233.

[30] Q. Wang, Y. Jiang, R. Sun, X.-Y. Tang, M. Shi, Chem. Eur. J. 2016, 22, 14739-14745. [31] M. Ackermann, PhD thesis, "Goldkatalysierte Zyklisierungsreaktionen", Heidelberg University,

2011.

[32] R. Döpp, PhD thesis, "Methodische Untersuchung von palladium- und goldkatalysierten