Serendipitous discovery of the catalytic hydroammoniumation and methylamination of alkynes

Article abstract of DOI:10.1002/anie.200905341

(Chemical equation presented) The gold rush: A cationic gold (I) complex, supported by a CAAC ligand, promotes the intramolecular addition of N-H or N-Me bonds (from ammonium salts or tertiary amines, respectively) to carbon-carbon triple bonds; the same complex allows for the isolation of vinylgold intermediates. X= (C₆F₅)₄B. CAAC = cyclic (alkyl) (amino)carbene.

Full text of DOI:10.1002/anie.200905341

Communications
DOI: 10.1002/anie.200905341
Gold Catalysis
Serendipitous Discovery of the Catalytic Hydroammoniumation and
Methylamination of Alkynes**
Xiaoming Zeng, Rei Kinjo, Bruno Donnadieu, and Guy Bertrand*
The transition-metal-catalyzed hydroamination reaction, that
of the phenyl spacer group places both the amino and the
alkyne moieties in the ideal positions to coordinate to the
metal center. The reaction of 1 with a stoichiometric amount
of cationic gold(I) complex B at room temperature was
monitored by multinuclear NMR spectroscopy. The instanta-
neous disappearance of both 1 and B was observed, along
with the formation of a new complex, which was isolated in
near quantitative yield. However, the spectroscopic data
suggested that it was not the desired tricoordinate gold(I)
complex of type I, but rather complex 2, presumably formed
from the coordination of the hydroamination product 3 to the
metal (Scheme 2). Even by monitoring the reaction at À708C,
À
is, the addition of an N H bond across a carbon-carbon
multiple bond, has been widely studied.[1,2] We have recently
reported that cationic gold(I) complexes,[3,4] supported by
cyclic (alkyl)(amino)carbene (CAAC) ligands,[5] readily cata-
lyze the intermolecular hydroamination of alkynes with a
variety of amines,[6] including ammonia.[6c] Based on prelimi-
nary mechanistic studies, we postulated that the key step of
the catalytic cycle was the formation of a tricoordinate gold
À
complex (I), which was followed by inner-sphere C N bond
formation, as first postulated by Tanaka et al.,[7a] and Nishina
and Yamamoto[7b,c] (Scheme 1). However, for other gold
Scheme 1. Possible intermediates I and II in the gold-catalyzed hydro-
amination of alkynes, and the gold complexes A and B used in this
study.
Scheme 2. Stoichiometric and catalytic gold(I)-catalyzed intramolecular
hydroamination of 1.
catalysts,[8] Che et al.[9a] and Li et al.[9b] hypothesized an outer-
sphere nucleophilic attack to the alkyne complex II, a
mechanism widely accepted for palladium[10] and platinum
complexes.[11] Herein, our attempts to isolate a gold(I)
complex of type I have led to the structural characterization
of two (CAAC)(h1-alkene)AuI complexes, and to the discov-
ery of two catalytic reactions: the intramolecular hydro-
ammoniumation using tertiary ammonium salts, and the
aminomethylation of carbon–carbon triple bonds.
no trace of starting material 1 could be observed, the
conversion into 2 being complete in a few seconds. The high
catalytic activity was confirmed using 5 mol% of B; at room
temperature, heterocycle 3 formed instantaneously in almost
quantitative yield. As expected, addition of one equivalent of
B to heterocycle 3 led cleanly to complex 2.
For obvious entropic reasons, intramolecular hydroami-
nation reactions occur under much milder conditions than
their intermolecular analogues, and therefore are better
suited for characterizing reaction intermediates. We first
chose N-methyl-2-(2-phenylethynyl)aniline (1), as the rigidity
To prevent the hydroamination process, and thereby
possibly characterize a putative tricoordinate gold(I) com-
plex, we prepared the corresponding tertiary amine 4a. A
stoichiometric amount of cationic gold(I) complex B was
added at room temperature to a solution of 4a in CDCl3, and
the reaction was monitored by NMR spectroscopy
(Scheme 3). Once again, we observed the instantaneous
disappearance of both 4a and B, and the clean formation of
a new complex 5, which was isolated in 98% yield. Surpris-
ingly, single-crystal X-ray diffraction[12] revealed that 5 was a
gold(I) h1-alkene complex resulting from the addition of the
tertiary amino group to the coordinated alkyne (Figure 1,
left). Complex 5 is structurally reminiscent of complexes
recently isolated by Hammond et al,[13] and Gagnꢀ et al.,[14]
from the gold-promoted cyclization of allenoates, and the
intramolecular hydroarylation of allenes, respectively.[15]
Interestingly, the formation of gold(I) h1-alkene complexes
of type 5 is not limited to the rigid 2-alkynyl-benzenamine 4a.
A mixture of (CAAC)AuCl(A)/AgOTf (1:1) instantaneously
[*] X. Zeng, Dr. R. Kinjo, B. Donnadieu, Prof. G. Bertrand
UCR-CNRS Joint Research Chemistry Laboratory (UMI 2957),
Department of Chemistry, University of California Riverside
Riverside, CA 92521-0403 (USA)
Fax: (+1)951-827-2725
E-mail: guy.bertrand@ucr.edu
Homepage: http://research.chem.ucr.edu/groups/bertrand/guy-
bertrandwebpage/
[**] We are grateful to the NIH (R01 GM 68825) and the DOE (DE-FG02-
09ER16069) for the financial support of this work, and to the China
Scholarship Council (X.Z.), and the Japan Society for the Promotion
of Science (R.K.) for fellowships.
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.200905341.
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gold catalyst, no cyclization occurred, even under heating a
CDCl3 solution of 9 in a sealed tube at 1208C for three days[18]
(Table 1, entry 1). In contrast, we were pleased to observe
that in the presence of 5 mol% of a 1:1 mixture of
(CAAC)AuCl(A)/AgOTf, derivative 9 underwent the desired
cyclization to form 8a in 98% yield after only 3 h at 708C
(Table 1, entry 2).
Table 1: Gold(I)-catalyzed intramolecular hydroammoniumation of 4
with HOTf.[a]
Scheme 3. Synthesis of complexes 5 and 7.
Entry
4
R1
R2
R3
T [8C] t [h]
8
Yield [%][b]
0[c]
1
2
3
4
5
6
7
4a Ph
4a Ph
4b p-Me-C6H4
4c p-MeO-C6H4 Me Me
4d nBu
4e Ph
4 f Ph
Me Me 120
Me Me
Me Me
72
3
8a
70
60
60
60
60
25
8a 98
8b 99
8c 99
8d 97
8e 94
8 f 99
2.5
2.5
2
Me Me
Me Et
Me Ph
7
0.5
[a] A (5 mol%), AgOTf (5 mol%), 4 (0.25 mmol), HOTf (0.25 mmol),
CDCl3 (0.4 mL). [b] Yields were determined by 1H NMR spectroscopy
using benzylmethyl ether as an internal standard. [c] No catalyst was
used.
Figure 1. ORTEP of gold complexes 5 (left) and 7 (right); ellipsoids set
at 50% probability. Hydrogen atoms, solvent molecules, and the
corresponding counterions are omitted for clarity.
reacted stoichiometrically at room temperature with aliphatic
N,N-diethylamino alkyne 6 to afford complex 7, which was
isolated in 95% yield and fully characterized (Figure 1, right).
Not surprisingly, treatment of complex 5 with one
equivalent of trifluoromethanesulfonic acid induced immedi-
ate proto-deauration,[2,16] affording the corresponding gold-
free cyclic ammonium salt 8a (Scheme 4). The stoichiometric
two-step transformation of 4a into 8a (through 5) led to the
question of whether this process could be catalytic for gold, or
if the presence of triflic acid would preferentially protonate
the basic tertiary amine,[7a,17] preventing the cyclization
process. Addition of one equivalent of triflic acid to solution
of alkynyl amine 4a in chloroform readily gave rise to the
corresponding acyclic ammonium salt 9. In the absence of the
Following a brief investigation into the scope of this
hydroammoniumation reaction, we found that aryl or alkyl
substituents were tolerated on the alkyne, and that the
cyclization process occurred under milder conditions when a
more weakly basic amine was used. For example, the hydro-
ammoniumation of 4 f readily occurred in a few minutes at
room temperature (Table 1, entry 7).
Examples in the literature of the direct carboamination of
alkynes (the addition of a carbon–nitrogen bond to a carbon–
carbon triple bond) are very rare. Yamamoto et al.[19] have
reported the platinum- and palladium-catalyzed intramolec-
À
ular C N bond addition of amides and N,O-acetals, and
Cacchi et al.[20] reported the palladium-catalyzed cyclization
of 2-alkynyl-N-allyl-N’-trifluoroacetyl benzenamine. Al-
though the cleavage of a relatively weak carbon–nitrogen
bond was involved in both cases, these results prompted us to
investigate the related methylamination reaction: in the
presence of 10 mol% of a 1:1 mixture of (CAAC)AuCl(A)/
KB(C6F5)4, 2-alkynyl-N,N’-dimethyl-benzenamines 4a–d was
transformed into 2,3-disubstituted indoles 10a–d in good to
excellent yields after 20 h at 1608C (Scheme 5). This rear-
rangement tolerates aryl or alkyl substituents on the alkyne.
However, in the case of the N-ethyl-N’-methyl-benzenamine
4e, loss of ethylene was observed, and the 3-unsubstituted
indole 3 was cleanly formed.
These results suggest that, at least for the intramolecular
variant, the gold-catalyzed hydroamination of alkynes does
not involve a tricoordinate gold complex of type I. Impor-
tantly, cationic gold(I) complexes supported by CAAC
ligands promote the intramolecular hydroammoniumation
Scheme 4. Stoichiometric and catalytic syntheses of 8a. X=TfO.
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(0.4 mL), the internal standard (benzyl methyl ether), derivatives 4
(0.25 mmol), and HOTf (37 mg, 0.25 mmol) were added, the tube was
sealed, placed in an oil bath, and heated at the specified temperature
(Table 1). The reaction was monitored by NMR spectroscopy.
General procedure for the catalytic methylamination of 4:
CAAC(AuCl) complex
A (0.030 g, 0.05 mmol) and KB(C6F5)4
(0.036 g, 0.05 mmol) were loaded in a dried J-Young-Tube. C6D6
(0.5 mL) and 4a–d (0.5 mmol) were then added. The tube was
sealed, placed in an oil bath, and heated at 1608C for 20 h.
Heterocycle 10a–d was purified by column chromatography on
silica gel (ethyl acetate/n-hexane 5:95).
Scheme 5. First examples of catalytic methylamination of alkyne.
Received: September 24, 2009
Revised: November 14, 2009
Published online: January 7, 2010
and methylamination reactions of alkynes. The scope of these
catalytic reactions is under investigation.
Keywords: alkynes · gold · homogeneous catalysis ·
.
hydroamination · methylamination
Experimental Section
All manipulations were performed under an atmosphere of dry argon
using standard Schlenk techniques.
Complex 2: A dried J-Young tube was loaded with gold complex
B (0.10 g, 0.074 mmol), 2-alkynyl-N-methyl-benzenamine 1 (0.016 g,
0.075 mmol), and CD2Cl2 (0.5 mL). The reaction was monitored by
NMR spectroscopy, and it had proceeded to completion after 5 min.
Removal of the solvent under vacuum and washing with n-hexane
gave gold complex 2 as a white solid (96% yield); m.p. 1608C;
13C NMR (126 MHz, CD2Cl2) d = 22.9 (CH3), 23.0 (CH3), 26.87
(CH3), 26.90 (CH3), 27.4 (CH), 28.4 (CH), 29.5 (CH ꢁ 2), 29.5 (CCH3),
29.6 (CCH3), 33.5 (NCH3), 34.6 (CH2 ꢁ 2), 35.4 (CH2), 35.9 (CH2),
37.39 (CH), 37.42 (CH), 39.1 (CH2), 48.6 (CH2), 64.6 (Cq), 67.1
(C(H)Au), 79.1 (Cq), 112.7 (CH), 122.1 (CH), 124.6 (br, Cq), 125.6
(CH), 125.8 (CH), 126.0 (CH), 126.2 (CH), 128.6 (Cq), 129.9 (CmH ꢁ 2
and CH ꢁ 2), 131.0 (CpH), 131.8 (CH), 134.0 (Cq), 135.7 (Ci), 136.9 (d,
[1] For recent reviews on hydroamination reactions, see: a) T. E.
Mꢂller, K. C. Hultzsch, M. Yus, F. Foubelo, M. Tada, Chem. Rev.
2008, 108, 3795 – 3892; b) R. Severin, S. Doye, Chem. Soc. Rev.
2007, 36, 1407 – 1420; c) I. Aillaud, J. Collin, J. Hannedouche, E.
Schulz, Dalton Trans. 2007, 5105 – 5118; d) S. Matsunaga, J.
Synth. Org. Chem. Jpn. 2006, 64, 778 – 779; e) P. W. Roesky, Z.
Anorg. Allg. Chem. 2006, 632, 1918 – 1926; f) A. L. Odom,
Dalton Trans. 2005, 225 – 233; g) N. Hazari, P. Mountford, Acc.
Chem. Res. 2005, 38, 839 – 849; h) J. F. Hartwig, Pure Appl.
Chem. 2004, 76, 507 – 516; i) S. Hong, T. J. Marks, Acc. Chem.
Res. 2004, 37, 673 – 686; j) M. Beller, J. Seayad, A. Tillack, H.
Jiao, Angew. Chem. 2004, 116, 3448 – 3479; Angew. Chem. Int.
Ed. 2004, 43, 3368 – 3398.
[2] For recent reviews on gold-catalyzed hydroamination, see: a) Z.
Li, C. Brouwer, C. He, Chem. Rev. 2008, 108, 3239 – 3265; b) A.
Arcadi, Chem. Rev. 2008, 108, 3266 – 3325; c) D. J. Gorin, B. D.
Sherry, F. D. Toste, Chem. Rev. 2008, 108, 3351 – 3378; d) N. T.
Patil, Y. Yamamoto, Chem. Rev. 2008, 108, 3395 – 3442; e) R. A.
Widenhoefer, Chem. Eur. J. 2008, 14, 5382 – 5391; f) N. Krause,
V. Belting, C. Deutsch, J. Erdsack, H. T. Fan, B. Gockel, A.
Hoffmann-Roder, N. Morita, F. Volz, Pure Appl. Chem. 2008, 80,
1063 – 1069; g) A. Fꢂrstner, P. W. Davies, Angew. Chem. 2007,
119, 3478 – 3519; Angew. Chem. Int. Ed. 2007, 46, 3410 – 3449;
h) R. A. Widenhoefer, X. Han, Eur. J. Org. Chem. 2006, 4555 –
4563.
[3] a) V. Lavallo, G. D. Frey, S. Kousar, B. Donnadieu, G. Bertrand,
Proc. Natl. Acad. Sci. USA 2007, 104, 13569 – 13573; b) G. D.
Frey, R. D. Dewhurst, S. Kousar, B. Donnadieu, G. Bertrand, J.
Organomet. Chem. 2008, 693, 1674 – 1682.
[4] A few examples of similar cationic gold(I) complexes, bearing
very bulky phosphine ligands, have been reported; see: E.
Herrero-Gꢃmez, C. Nieto-Oberhuber, S. Lꢃpez, J. Benet-
Buchholz, A. M. Echavarren, Angew. Chem. 2006, 118, 5581 –
5585; Angew. Chem. Int. Ed. 2006, 45, 5455 – 5459.
[5] a) V. Lavallo, Y. Canac, C. Prꢄsang, B. Donnadieu, G. Bertrand,
Angew. Chem. 2005, 117, 5851 – 5855; Angew. Chem. Int. Ed.
2005, 44, 5705 – 5709; b) V. Lavallo, Y. Canac, A. DeHope, B.
Donnadieu, G. Bertrand, Angew. Chem. 2005, 117, 7402 – 7405;
Angew. Chem. Int. Ed. 2005, 44, 7236 – 7239; c) R. Jazzar, R. D.
Dewhurst, J.-B. Bourg, B. Donnadieu, Y. Canac, G. Bertrand,
Angew. Chem. 2007, 119, 2957 – 2960; Angew. Chem. Int. Ed.
2007, 46, 2899 – 2902; d) R. Jazzar, J.-B. Bourg, R. D. Dewhurst,
B. Donnadieu, G. Bertrand, J. Org. Chem. 2007, 72, 3492 – 3499.
[6] a) X. Zeng, G. D. Frey, R. Kinjo, B. Donnadieu, G. Bertrand, J.
Am. Chem. Soc. 2009, 131, 8690 – 8696; b) X. Zeng, G. D. Frey, S.
Kousar, G. Bertrand, Chem. Eur. J. 2009, 15, 3056 – 3060; c) V.
Lavallo, G. D. Frey, B. Donnadieu, M. Soleilhavoup, G. Ber-
J
CF = 242.8 Hz, Cq), 138.9 (d, JCF = 242.6 Hz, Cq), 140.8 (Cq), 145.1
(Co), 145.8 (Co), 148.8 (d, JCF = 238.3 Hz, Cq), 164.4 (Cq), 242.7 ppm
(Ccarbene).
Complex 5: A dried J-Young tube was loaded with gold complex
B (0.15 g, 0.112 mmol), amino alkyne 4a (0.025 g, 0.112 mmol), and
CDCl3 (0.4 mL). After 5 min, the solvent was removed under vacuum,
and the solid residue washed with n-hexane to give complex 5 as a
white solid (98% yield). Single crystals were obtained by recrystal-
lization from a CH2Cl2/n-hexane/toluene (10:20:1) solution at À208C;
m.p. 2438C; 13C NMR (75 MHz, CDCl3): d = 23.0 (CH3), 26.5 (CH3),
27.0 (CH), 27.8 (CH), 29.0 (CH), 29.1 (CH3), 34.2 (CH2), 35.2 (CH2),
37.1 (CH), 38.8 (CH2), 48.4 (CH2), 51.9 (CH3), 65.1 (Cq), 77.9 (Cq),
115.5 (CH), 125.0 (CH), 127.7 (CH), 128.0 (CH), 129.3 (CH), 129.6
(CH), 130.3 (CH), 130.7 (CH), 132.2 (CH), 135.4 (Cq), 136.3 (d, JCF
=
246.6 Hz, Cq), 138.2 (d, JC-F = 245.4 Hz, Cq), 142.7 (Cq), 144.9 (Cq),
145.3 (Cq), 147.6 (Cq), 138.3 (d, JC-F = 239.5 Hz, Cq), 154.7 (Cq), 159.5
(Cq), 259.7 ppm (Ccarbene).
Complex 7: Complex A (0.043 g, 0.071 mmol) and AgOTf
(0.021 g, 0.071 mmol) were loaded in a dried J-Young tube; CDCl3
(0.4 mL) and 6 (0.015 g, 0.071 mmol) were added, and the tube was
sealed. The reaction was monitored by NMR spectroscopy. After
removing the solvent under vacuum, the residue was washed with n-
hexane to give gold complex 7 as a white solid (95% yield). Single
crystals were obtained by recrystallization from a CHCl3/n-hexane
(1:1) solution at À208C; m.p. 1998C; 13C NMR (126 MHz, CDCl3):
d = 9.7 (CH3), 22.9 (CH2), 23.4 (CH3), 26.1 (CH3), 27.2 (CH), 28.0
(CH), 29.1 (CH), 29.4 (CH3), 34.5 (CH2), 35.2 (CH2), 36,3 (CH2), 37.2
(CH), 39.0 (CH2), 49.0 (CH2), 60.6 (CH2), 63.1 (CH2), 64.7 (Cq), 77.9
(Cq), 121.0 (Cq, q, JCF = 320.5 Hz), 123.1 (CH), 124.1 (CH), 125.0
(CH), 128.3 (CH), 129.6 (CH), 133.0 (Cq), 136.2 (Cq), 145.2 (Cq), 145.3
(Cq), 161.5 (Cq), 258.5 ppm (Ccarbene).
General procedure for the catalytic hydroammoniumation reac-
tion: CAAC(AuCl) complex A (0.008 g, 0.0125 mmol) and AgOTf
(0.003 g, 0.0125 mmol) were loaded in a dried J-Young tube; CDCl3
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trand, Angew. Chem. 2008, 120, 5302 – 5306; Angew. Chem. Int.
Ed. 2008, 47, 5224 – 5228.
free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
[7] a) E. Mizushima, T. Hayashi, M. Tanaka, Org. Lett. 2003, 5,
3349 – 3352; b) N. Nishina, Y. Yamamoto, Angew. Chem. 2006,
118, 3392 – 3395; Angew. Chem. Int. Ed. 2006, 45, 3314 – 3317;
c) N. Nishina, Y. Yamamoto, Tetrahedron 2009, 65, 1799 – 1808.
[8] Labeling experiments that support trans addition have been
reported for other gold-catalyzed reactions: a) J. J. Kennedy-
Smith, S. T. Staben, F. D. Toste, J. Am. Chem. Soc. 2004, 126,
4526 – 4527; b) A. S. K. Hashmi, J. P. Weyrauch, W. Frey, J. W.
Bats, Org. Lett. 2004, 6, 4391 – 4394.
[13] L. Liu, B. Xu, M. S. Mashuta, G. B. Hammond, J. Am. Chem.
Soc. 2008, 130, 17642 – 17643.
[14] D. Weber, M. A. Tarselli, M. R. Gagnꢀ, Angew. Chem. 2009, 121,
5843 – 5846; Angew. Chem. Int. Ed. 2009, 48, 5733 – 5736.
[15] See also: a) G. Seidel, R. Mynott, A. Fꢂrstner, Angew. Chem.
2009, 121, 2548 – 2551; Angew. Chem. Int. Ed. 2009, 48, 2510 –
2513; b) J. A. Akana, K. X. Bhattacharyya, P. Miller, J. P.
Sadighi, J. Am. Chem. Soc. 2007, 129, 7736 – 7737.
[16] a) D. J. Gorin, F. D. Toste, Nature 2007, 446, 395 – 403;
b) A. S. K. Hashmi, G. J. Hutchings, Angew. Chem. 2006, 118,
8064 – 8105; Angew. Chem. Int. Ed. 2006, 45, 7896 – 7936.
[17] a) C. F. Bender, R. A. Widenhoefer, Chem. Commun. 2008,
2741 – 2743; b) A. S. K. Hashmi, Catal. Today 2007, 122, 211 –
214; c) G. Kovꢅcs, G. Ujaque, A. Lledꢃs, J. Am. Chem. Soc. 2008,
130, 853 – 864.
[18] A few examples of acid-catalyzed hydroaminations have been
reported; see: a) B. Schlummer, J. F. Hartwig, Org. Lett. 2002, 4,
1471 – 1474; b) K. Motokura, N. Nakaagiri, K. Mori, T. Miz-
ugaki, K. Ebitani, K. Jitsukawa, K. Kaneda, Org. Lett. 2006, 8,
4617 – 4620; c) D. C. Rosenfeld, S. Shekhar, A. Takemiya, M.
Utsunomiya, J. F. Hartwig, Org. Lett. 2006, 8, 4179 – 4182;
d) L. L. Anderson, J. Arnold, R. G. Bergman, J. Am. Chem.
Soc. 2005, 127, 14542 – 14543; e) A. A. M. Lapis, B. A. DaSil-
veira Neto, J. D. Scholten, F. A. Nachtigall, M. N. Eberlin, J.
Dupont, Tetrahedron Lett. 2006, 47, 6775 – 6779; f) Z. G. Li, J. L.
Zhang, C. Brouwer, C. G. Yang, N. W. Reich, C. He, Org. Lett.
2006, 8, 4175 – 4178.
[9] a) C. Y. Zhou, P. W. H. Chan, C. M. Che, Org. Lett. 2006, 8, 325 –
328; b) Y. Zhang, J. P. Donahue, C. J. Li, Org. Lett. 2007, 9, 627 –
630.
[10] a) H. Cao, L. McNamee, H. Alper, Org. Lett. 2008, 10, 5281 –
5284; b) N. T. Patil, H. Wu, Y. Yamamoto, J. Org. Chem. 2007,
72, 6577 – 6579; c) G. B. Bajracharya, Z. Huo, Y. Yamamoto, J.
Org. Chem. 2005, 70, 4883 – 4886; d) L. M. Lutete, I. Kadota, Y.
Yamamoto, J. Am. Chem. Soc. 2004, 126, 1622 – 1623; e) J.
Penzien, R. Q. Su, T. E. Mꢂller, J. Mol. Catal. A 2002, 183, 489 –
498; f) R. Q. Su, T. E. Mꢂller, Tetrahedron 2001, 57, 6027 – 6033;
g) T. E. Mꢂller, M. Berger, M. Grosche, E. Herdtweck, F. P.
Schmidtchen, Organometallics 2001, 20, 4384 – 4393; h) J.
Takaya, J. F. Hartwig, J. Am. Chem. Soc. 2005, 127, 5756 –
5757; i) S. Tobisch, Chem. Eur. J. 2007, 13, 4884 – 4894; j) C.
Mꢂller, R. Koch, S. Doye, Chem. Eur. J. 2008, 14, 10430 – 10436;
k) U. Nettekoven, J. F. Hartwig, J. Am. Chem. Soc. 2002, 124,
1166 – 1167; l) B. M. Cochran, F. E. Michael, J. Am. Chem. Soc.
2008, 130, 2786 – 2792.
[11] a) N. T. Patil, R. D. Kavthe, V. S. Raut, V. V. N. Reddy, J. Org.
Chem. 2009, 74, 6315 – 6318; b) J. L. McBee, A. T. Bell, T. D.
Tilley, J. Am. Chem. Soc. 2008, 130, 16562 – 16571.
[12] CCDC 748500 (5) and 748501 (7) contain the supplementary
crystallographic data for this paper. These data can be obtained
[19] a) I. Nakamura, Y. Mizushima, U. Yamagishi, Y. Yamamoto,
Tetrahedron 2007, 63, 8670 – 8676; b) T. Shimada, I. Nakamura,
Y. Yamamoto, J. Am. Chem. Soc. 2004, 126, 10546 – 10547.
[20] a) S. Cacchi, J. Organomet. Chem. 1999, 576, 42 – 64; b) S.
Cacchi, G. Fabrizi, P. Pace, J. Org. Chem. 1998, 63, 1001 – 1011.
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