An effective and versatile strategy for the synthesis of structurally diverse heteroarylsilanesviaIr(iii)-catalyzed C-H silylation

Article abstract of DOI:10.1039/d1sc02344f

A versatile silylation of heteroaryl C-H bonds is accomplished under the catalysis of a well-defined spirocyclic NHC Ir(iii) complex (SNIr), generating a variety of heteroarylsilanes. A significant advantage of this catalytic system is that multiple types of intermolecular C-H silylation can be achieved using one catalytic system at α, β, γ, or δ positions of heteroatoms with excellent regioselectivities. Mechanistic experiments and DFT calculations indicate that the polycyclic ligand of SNIr can form an isolable cyclometalated intermediate, which leaves a phenyl dentate free and provides a hemi-open space for activating substrates. In general, favorable silylations occur at γ or δ positions of chelating heteroatoms, forming 5- or 6-membered C-Ir-N cyclic intermediates. If such an activation mode is prohibited sterically, silylations would take place at the α or β positions. The mechanistic studies would be helpful for further explaining the reactivity of the SNIr system.

Full text of DOI:10.1039/d1sc02344f

Chemical
Science
View Article Online
View Journal | View Issue
EDGE ARTICLE
An effective and versatile strategy for the synthesis
of structurally diverse heteroarylsilanes via Ir(III)-
catalyzed C–H silylation†
Cite this: Chem. Sci., 2021, 12, 9748
All publication charges for this article
have been paid for by the Royal Society
of Chemistry
ab
Zhi-Bo Yan,a Meng Peng,a Qi-Long Chen,a Ka Lu,a Yong-Qiang Tu,
*
a
a
Kun-Long Dai,a Fu-Min Zhang
and Xiao-Ming Zhang
A versatile silylation of heteroaryl C–H bonds is accomplished under the catalysis of a well-defined
spirocyclic NHC Ir(III) complex (SNIr), generating a variety of heteroarylsilanes. A significant advantage of
this catalytic system is that multiple types of intermolecular C–H silylation can be achieved using one
catalytic system at a, b, g, or d positions of heteroatoms with excellent regioselectivities. Mechanistic
experiments and DFT calculations indicate that the polycyclic ligand of SNIr can form an isolable
cyclometalated intermediate, which leaves a phenyl dentate free and provides a hemi-open space for
activating substrates. In general, favorable silylations occur at g or d positions of chelating heteroatoms,
forming 5- or 6-membered C–Ir–N cyclic intermediates. If such an activation mode is prohibited
sterically, silylations would take place at the a or b positions. The mechanistic studies would be helpful
for further explaining the reactivity of the SNIr system.
Received 27th April 2021
Accepted 8th June 2021
DOI: 10.1039/d1sc02344f
rsc.li/chemical-science
In 2009, a distinctive strategy of using easily-installed and
-removed 2-pyrazol-5-ylaniline as a directing group for o-silyla-
tion of arylboronic acids has been developed by Suginome.6b
Introduction
Organosilanes have emerged as an important class of
compounds with diverse utilities,1 serving as versatile organic
reagents to mediate many novel organic reactions,1a,2 functional
materials,3 therapeutic pharmaceuticals, and bioactive chem-
icals (Scheme 1).4 Traditionally, silicon-containing molecules
have been prepared through the reactions of equivalent
organometallic species with electrophilic silicon reagents,5
which suffer from inferior atom-economy and low functional-
group tolerance. For several decades, transition-metal-
catalyzed intermolecular direct C–H silylation has been devel-
oped as a more efficient and attractive strategy.1c–e Among them,
C(sp2)–H silylation can generally be promoted with a directing
group, which could coordinate with the metal center to form
cyclometalated species and thus improve the regioselectivity of
reaction. In this eld, a range of directing groups have been
developed,6 which include strongly coordinating pyridines and
various azoles, and more weakly coordinating imines, amides,
esters, and ketones. In particular, Hou reported an alkoxyl-
directed Sc-catalyzed silylation of various anisole derivatives.6a
In comparison, undirected C(sp2)–H silylation7 is more
challenging due to the loss of interaction between the coordi-
nating group and the catalyst. A breakthrough in undirected
silylation was established by Hartwig,7a which takes advantage
aState Key Laboratory of Applied Organic Chemistry, College of Chemistry and
Chemical Engineering, Lanzhou University, Lanzhou 730000, P. R. China. E-mail:
tuyq@lzu.edu.cn
bSchool of Chemistry and Chemical Engineering, Frontiers Science Center for
Transformative Molecules, Shanghai Key Laboratory for Molecular Engineering of
Chiral Drugs, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
† Electronic supplementary information (ESI) available. CCDC 2068360, 2054626
and 2054624. For ESI and crystallographic data in CIF or other electronic format
see DOI: 10.1039/d1sc02344f
Scheme
silylation.
1 Representative organosilanes and intermolecular C–H
9748 | Chem. Sci., 2021, 12, 9748–9753
© 2021 The Author(s). Published by the Royal Society of Chemistry

View Article Online
Edge Article
Chemical Science
of steric effects in controlling regioselectivities. In addition, Et3SiH (2 equiv.) were added for further reaction. The results are
C(sp3)–H bond silylation at the benzylic position8 of the summarized in Table 1. To our delight, the chloride catalyst B
aromatic ring or next to the heteroatom such as nitrogen9 or could give the highest yield of the desired silylation product 2a
sulfur10 was also reported, which has expanded the substrate (entries 2 vs. 1 and 3), and no reaction was observed in the
scope and applicability of silylation reaction. Despite those absence of Ir catalysts or hydrogen acceptors (entries 4 and 5).
precedent achievements on either directed or undirected C–H Further investigation found that tert-butylethylene (tbe) was the
silylation reactions, a certain catalytic system could usually be most effective hydrogen acceptor (entries 7 vs. 2 and 6). When
used to activate a specic type of substrate. Therefore, devel- an increased loading (5 mol%) of B was used in o-xylene solvent,
opment of a more general catalytic system for C–H silylation of the yield was improved to 85% (entries 9 vs. 7 and 8). Notably,
multiple types of substrates with high regioselectivities for each when all reactants and catalysts were added to the reaction
type of reaction would be in high demand, considering the simultaneously, the system would become complicated and give
versatility of this strategy.
a relatively low yield (entry 11).
With the optimized conditions in hand,12 the substrate scope
of g silylations with a series of 2-phenylpyridine substrates was
rst explored. As shown in Table 2, high yields and regiose-
Results and discussion
In our previous work, we have developed a well-dened dia- lectivities were obtained in most cases, while the reaction effi-
nionic Ir(III) CCC pincer catalyst (SNIr),11 which features unique ciency could be inuenced with the variation of the substitution
double C(sp2)–H bond activation in a polycyclic ligand frame- pattern of substrates. Specically, for substituted 2-phenyl-
work. This unexpected chelation mode reminds us that the pyridine (1a–1j), the o- or p-methyl substitution on the benzene
central Ir may potentially enable C–H activation upon cleavage ring gave better product yields (83% for 2b, 87% for 2d)
of the phenyl Ir–C bond to provide a hemi-open space for compared with the m-substitution (51% for 2c). The substrates
substrate activation under certain conditions. Base on this with the p-EDG substituted phenyl group could give much
hypothesis, we have developed a versatile strategy for Ir(III)- higher yields than those with p-EWD substitution (2d and 2g vs.
catalyzed C–H silylation of diverse heteroarylsilanes. Herein we 2e and 2f). A signicant substituent effect was also observed on
present our research results.
We started our investigation with 2-phenylpyridine 1a as the
Table 2 Dehydrogenative silylation of g C–H bonds of heteroarenesa
model substrate and Et3SiH as the silane source to screen the
catalysts A–C. A mixture of 1a and A–C (2.5–5 mol%) was rst
stirred at 100 ꢀC for 6 h. Then a hydrogen acceptor (3 equiv.) and
Table 1 Optimization of the reaction conditionsa
Entry Cat. (mol%) Additive
Solvent
Temp. (ꢀC) Yieldb (%)
1
2
3
4
A (2.5)
B (2.5)
C (2.5)
None
Cyclohexene Toluene 100
Cyclohexene Toluene 100
Cyclohexene Toluene 100
Cyclohexene Toluene 150
22
46
<5
0
5
6
7
8
B (2.5)
B (2.5)
B (2.5)
B (5.0)
B (5.0)
B (5.0)
B (5.0)
None
nbe
tbe
tbe
tbe
Toluene 150
Toluene 100
Toluene 100
Toluene 100
o-Xylene 100
o-Xylene 80
o-Xylene 100
0
26
60
78
9
85 (80)c
63
10
tbe
tbe
11d
66
a
Unless otherwise specied, reactions were conducted by pretreatment
of a solution of 1a (0.5 mmol), cat. (2.5–5 mol%) and solvent (2 mL) at
a given temperature for 6 h, and then the additive (3 equiv.) and
Et3SiH (2 equiv.) were added for further reaction. b Determined by GC-
a
Unless otherwise specied, reactions were conducted by pretreatment
of a solution of 1 (0.5 mmol) and cat. B (5 mol%) in o-xylene (2 mL) at
100 ꢀC for 6 h, and then tbe (3 equiv.) and Et3SiH (2 equiv.) were
b
c
MS (internal standard: dodecane). Isolated yield in parentheses. d No
added for further reaction. Trace amount (<5%) of monosilylation
c
product could be detected by GC-MS. At 140 ꢀC, starting materials
pretreatment. nbe ¼ 2-norbornene, tbe ¼ tert-butylethylene.
recycled. d Ph3SiH, Ph2MeSiH, or PhMe2SiH was used instead of Et3SiH.
© 2021 The Author(s). Published by the Royal Society of Chemistry
Chem. Sci., 2021, 12, 9748–9753 | 9749

View Article Online
Chemical Science
Edge Article
different positions of the pyridine ring. For example, 2-methyl cyclometalated intermediates. Similarly, both electron and
substitution afforded a higher yield than 3,4-substitutions (2h steric effects of the benzyl group showed signicant inuence
vs. 2i and 2j). The scope could be further extended to benzo- on the reaction outcome. For example, p-EDG substituted
fused substrates (1k–1p), whose reactions could generally afford substrates gave higher yields than the p-EWG substituted ones
the desired products in good to high yields (75–92%). Notably, in general sense (4d and 4e vs. 4i and 4k). However, for the o- or
2-phenylquinoline and 1-phenylisoquinoline could give excel- m-substitutions, both reactions were sluggish and gave poor to
lent higher yields (92% for 2l, 90% for 2o). Moreover, for other moderate yields regardless of either EDG or EWG substituents
N-heteroarenes, such as azo-, pyrazolyl-, and iminyl-arenes (1q– (4f, 4g and 4j). Delightedly, 2-phenoxypyridine afforded the best
1t), they were also amenable in the reaction, affording the cor- result (94% for 4h), probably because of the double activation of
responding products with high efficiency. In particular, the same C–H bond (N to d-C and O to b-C) and electro-donating
substrates 1s and 1t could mainly give disilylation products in effect of the ether group. Compared with g C–H silylations of
moderate yields along with a trace amount of monosilylation benzo-phenyl pyridines (92% for 2l, 90% for 2o, Table 2), a slow
product. Besides, our catalytic system was also well effective reaction rate and decreased product yields were observed for
toward more inert g C(sp3)–H bonds linked to heteroarenes. As these d-silylations (74% for 4m, 65% for 4n).
a representative example, 8-methylquinoline could afford the g-
Finally, we investigated more universal and practically useful
silylation product 2u in 95% yield. The reactions of 2,6-dieth- heteroarenes (Table 4), and these silylation reactions showed
ylpyridine (1v) and 2-dimethylaminopyridine (1w) were also extremely good regioselectivities and broad substrate scope. For
feasible, giving products in moderate yields under conditions thiophene (5a, 5j and 5k) and furan (5b and 5l) derivatives,
with elevated temperature. Remarkably, our catalytic system silylations generally took place at a positions with good yields,
also accommodated the silylation of 1a with other hydrosilanes, which complemented the normal electrophilic Friedel–Cras
such as Ph3SiH, Ph2MeSiH, or PhMe2SiH with good regiose- silylation reactions.1e,14 Further investigation was focused on the
lectivities (2x–2z). It is worth nothing that in all cases we were derivatives of indole 5c–5i as they have practical utilities in the
not able to detect other a, b or d silylation products.
elds of natural products and drug discovery.15 In general,
Subsequent investigation was carried out toward the d-sily- silylation always occurred at C-2 positions of indoles except for
lation of 2-benzylpyridine 3,13 and the desired products could be N-tosyl substituted indole, which directed the silylation to an
generated in good to high yields in most cases (Table 3). unusual b-position (6d).7d The results of a-silylations of indoles
Generally, a higher reaction temperature (120 ꢀC) was required indicated that EDG substitutions would give better outcomes
than the corresponding g C–H silylation, possibly due to than the EWG substitutions (6e–6g vs. 6h and 6i). As for the
a higher activation energy for the formation of the 6-membered substituted 2-methyl quinolines and benzo(b)quinoline, b-sily-
lation would occur to afford 6m–6p in moderate to good yields.
Moreover, this catalytic mode was also well effective toward the
Table 3 Dehydrogenative silylation of d C–H bonds of heteroarenesa
Table 4 Regioselective dehydrogenative silylation of a, b C–H bonds
of N,O,S-heteroarenesa
a
Unless otherwise specied, reactions were conducted by pretreatment
a
Unless otherwise specied, reactions were conducted by pretreatment of a solution of 5 (0.5 mmol) and cat. B (5 mol%) in o-xylene (0.5 mL) at
of a solution of 3 (0.5 mmol) and cat. B (5 mol%) in o-xylene (0.5 mL) at 120 ꢀC for 6 h, and then tbe (3 equiv.) and Et3SiH (2 equiv.) were added
b
c
120 ꢀC for 6 h, and then tbe (1.5 equiv.) and Et3SiH (3 equiv.) were added for further reaction. b-silylation was observed. At 140 ꢀC, starting
for further reaction.
materials recycled.
9750 | Chem. Sci., 2021, 12, 9748–9753
© 2021 The Author(s). Published by the Royal Society of Chemistry

View Article Online
Edge Article
Chemical Science
Fig. 1 Energy profiles of the Ir-catalyzed silylation of 3a at 120 ꢀC.
b C–H silylation of arene directed by sp3-N (5q) or the more inert neohexane and formation of the Ir–Si intermediate IM5 in the
b C(sp3)–H bond (5r).
presence of Et3SiH. Thereaer, Ir(I) species IM6 was generated
Computational studies were next conducted to explore the by reductive elimination of IM5 through TS4. Finally, exchange
mechanism using 3a (2-BnPy) as a model (Fig. 1).6f,16,17 Initially, of the silylation products 4a to 2-BnPy followed by oxidative
the cod ligand of cat. B was dissociated from Ir before coordi- addition of Ir to the d C–H bond of intramolecular 2-BnPy
nation of the N atom of 2-BnPy. Next, s-metathesis between the regenerated the active Ir–H species IM3 and completed the
phenyl C–Ir and d C–H bonds of the 2-BnPy moiety easily took catalytic cycle.
place through TS1 to form a stable 6-membered intermediate
To further probe the mechanism, several control experi-
IM1, which then reacted with Et3SiH to give the Ir–H species IM3 ments were conducted (Fig. 2). First, reactions of 1b or 3d and
ꢀ
with the formation of Et3SiCl. As the catalytic cycle begins, the catalyst B without Et3SiH at 120 C for 6 h could generate two
hydride of IM3 was captured by the hydrogen acceptor (tbe) in brown complexes 1bB and 3dB in 88% and 92% yields,
the system to give Ir-alkyl species IM4. Then the o-C–H activa- respectively. 1H NMR, high resolution mass spectroscopy
tion of the side-phenyl occurred through TS3 with the release of (HRMS) and X-ray analysis conrmed that these complexes
contained either a 5- or 6-membered C–Ir–N ring formed from
the substrates and catalyst, and both intermediates had a free
phenyl group dissociated with Ir.18 Furthermore, the silylation
products 2b and 4d could be generated in 65% and 77% yields,
respectively, when 5 mol% 1bB or 3dB was directly used as
a catalyst under standard conditions. These results suggested
that the iridacycle intermediates might serve as the pre-catalysts
during the reaction process. Next, the H/D exchange experiment
indicated that the C–H bond activation step might be irrevers-
ible (Fig. 2b). The kinetic isotope effect experiment showed
a value of 3.1 from two parallel reactions and a KIE of 2.4 from
intermolecular competition, which indicated that the C–H bond
cleavage process was likely involved in the rate-determining
step (Fig. 2c).
Conclusions
In summary, we have developed a general catalyst system based
on SNIr for intermolecular C–H silylation of a wide range of
substrate types with excellent regioselectivities and good to high
yields. In all examples, single silylation products can be ob-
Fig. 2 Mechanistic experiments.
tained in high regioselectivities. Mechanistic experiments and
© 2021 The Author(s). Published by the Royal Society of Chemistry
Chem. Sci., 2021, 12, 9748–9753 | 9751

View Article Online
Chemical Science
Edge Article
DFT calculations indicated the intermediate species and an
Ir(III)/Ir(I) mechanism in the catalytic cycle. This methodology
we established here would probably shed some new light on
dianionic pincer complexes both in academic and applied
research.
Med. Chem., 2013, 56, 388; (d) R. Ramesh and D. S. Reddy,
J. Med. Chem., 2018, 61, 3779.
5 (a) S. E. Denmark and L. Neuville, Org. Lett., 2000, 2, 3221; (b)
M. Nakano, S. Shinamura, R. Sugimoto, I. Osaka, E. Miyazaki
and K. Takimiya, Org. Lett., 2012, 14, 5448.
6 Selected examples of directed C(sp2)–H silylation: (a)
J. Oyamada, M. Nishiura and Z. Hou, Angew. Chem., Int.
Ed., 2011, 50, 10720; (b) H. Ihara and M. Suginome, J. Am.
Chem. Soc., 2009, 131, 7502; (c) T. Mita, K. Michigami and
Y. Sato, Org. Lett., 2012, 14, 3462; (d) N. A. Williams,
Y. Uchimaru and M. Tanaka, J. Chem. Soc., Chem.
Commun., 1995, 1129; (e) G. Choi, H. Tsurugi and
K. Mashima, J. Am. Chem. Soc., 2013, 135, 13149; (f)
Data availability
The datasets supporting this article have been uploaded as part
of the ESI.†
Author contributions
´
´
L. Rubio-Perez, M. Iglesias, J. Munarriz, V. Polo,
Z.-B. Yan performed all of the experiments and prepared the
ESI;† M. Peng prepared materials and catalysts for silylation
reactions; K. Lu performed the computational studies; Y.-Q. Tu
and Z.-B. Yan wrote the manuscript; all authors provided input
on the manuscript.
´
V. Passarelli, J. J. Perez-Torrente and L. A. Oro, Chem. Sci.,
2017, 8, 4811; (g) A. Maji, S. Guin, S. Feng, A. Dahiya,
V. K. Singh, P. Liu and D. Maiti, Angew. Chem., Int. Ed.,
2017, 56, 14903; (h) E. M. Simmons and J. F. Hartwig, J.
Am. Chem. Soc., 2010, 132, 17092; (i) T. A. Boebel and
J. F. Hartwig, J. Am. Chem. Soc., 2008, 130, 7534; (j)
J.-L. Pan, C. Chen, Z.-G. Ma, J. Zhou, L.-R. Wang and
S.-Y. Zhang, Org. Lett., 2017, 19, 5216; (k) W. Li, W. Chen,
B. Zhou, Y. Xu, G. Deng, Y. Liang and Y. Yang, Org. Lett.,
2019, 21, 2718.
Conflicts of interest
The authors declare no conict of interest.
7 Selected examples of undirected C(sp2)–H silylation: (a)
C. Cheng and J. F. Hartwig, Science, 2014, 343, 853; (b)
H. Fang, L. Guo, Y. Zhang, W. Yao and Z. Huang, Org. Lett.,
2016, 18, 5624; (c) C. Cheng and J. F. Hartwig, J. Am. Chem.
Soc., 2015, 137, 592; (d) B. Lu and J. R. Falck, Angew.
Chem., Int. Ed., 2008, 47, 7508; (e) A. A. Toutov, W.-B. Liu,
K. N. Betz, A. Fedorov, B. M. Stoltz and R. H. Grubbs,
Nature, 2015, 518, 80; (f) A. A. Toutov, W.-B. Liu, K. N. Betz,
B. M. Stoltz and R. H. Grubbs, Nat. Protoc., 2015, 10, 1897;
(g) Q. Yin, H. F. T. Klare and M. Oestreich, Angew. Chem.,
Int. Ed., 2016, 55, 3204; (h) Y. Ma, B. Wang, L. Zhang and
Z. Hou, J. Am. Chem. Soc., 2016, 138, 3663; (i) M. Murai,
N. Nishinaka and K. Takai, Angew. Chem., Int. Ed., 2018,
57, 5843; (j) L. Zhang, K. An, Y. Wang, Y.-D. Wu, X. Zhang,
Z.-X. Yu and W. He, J. Am. Chem. Soc., 2021, 143, 3571.
8 (a) F. Kakiuchi, K. Tsuchiya, M. Matsumoto, E. Mizushima
and N. Chatani, J. Am. Chem. Soc., 2004, 126, 12792; (b)
Y. Kuninobu, T. Nakahara, H. Takeshima and K. Takai,
Org. Lett., 2013, 15, 426.
Acknowledgements
We thank the NSFC (No. 21871117, 21702136, 21502080, and
21772071), the “111” Program of MOE, the Major project
(2018ZX09711001-005-002) of MOST, and the STCSM
(19JC1430100) for the nancial support. This work was sup-
ported by the High-Performance Computing Center (HPCC) of
Shanghai Jiao Tong University. Also, we thank Zi-Hao Li from
the Shanghai Jiao Tong University for his helpful discussion.
Notes and references
1 (a) C. Cheng and J. F. Hartwig, Chem. Rev., 2015, 115, 8946;
(b) R. Sharma, R. Kumar, I. Kumar, B. Singh and
U. Sharma, Synthesis, 2015, 47, 2347; (c) T. Komiyama,
Y. Minami and T. Hiyama, ACS Catal., 2017, 7, 631; (d)
H. T. Huang, T. Li, J. Z. Wang, G. P. Qin and T. B. Xiao,
Chin. J. Org. Chem., 2019, 39, 1511; (e) S. C. Richter and
M. Oestreich, Trends Chem., 2020, 2, 13.
2 (a) S. E. Denmark and R. F. Sweis, Metal-Catalyzed Cross-
Coupling Reactions, ed. A. De Meijere and F. Diederich,
Wiley-VCH, Weinheim, 2nd edn, 2004, vol. 1, pp. 163–216;
9 (a) T. Mita, K. Michigami and Y. Sato, Chem.–Asian J., 2013, 8,
2970; (b) H. Fang, W. Hou, G. Liu and Z. Huang, J. Am. Chem.
Soc., 2017, 139, 11601.
(b) B. Yang, W. Yang, Y. Guo, L. You and C. He, Angew. 10 T. Luo, H.-L. Teng, C. Xue, M. Nishiura and Z. Hou, ACS
Chem., Int. Ed., 2020, 59, 22217; (c) H. Chen, Y. Chen, Catal., 2018, 8, 8027.
X. Tang, S. Liu, R. Wang, T. Hu, L. Gao and Z. Song, 11 Z.-B. Yan, K.-L. Dai, B.-M. Yang, Z.-H. Li, Y.-Q. Tu,
Angew. Chem., Int. Ed., 2019, 58, 4695; (d) L. T. Ball,
G. C. Lloyd-Jones and C. A. Russell, Science, 2012, 337, 1644.
F.-M. Zhang, X.-M. Zhang, M. Peng, Q.-L. Chen and
Z.-R. Jing, Sci. China: Chem., 2020, 63, 1761.
3 (a) T. Kumagai and S. Itsuno, Macromolecules, 2002, 35, 5323; 12 For detailed condition screening of g C–H silylations, see
(b) P. M. Zelisko, Bio-Inspired Silicon-Based Materials,
Springer, Dordrecht, The Netherlands, 2014.
4 (a) A. K. Franz, Curr. Opin. Drug Discovery Dev., 2007, 10, 654;
(b) M. Mortensen, R. Husmann, E. Veri and C. Bolm, Chem.
Soc. Rev., 2009, 38, 1002; (c) A. K. Franz and S. O. Wilson, J.
ESI, Section 3.1.†
13 For detailed condition screening of d C–H silylations, see
ESI, Section 4.1.†
9752 | Chem. Sci., 2021, 12, 9748–9753
© 2021 The Author(s). Published by the Royal Society of Chemistry

View Article Online
Edge Article
Chemical Science
¨
14 (a) S. Bahr and M. Oestreich, Angew. Chem., Int. Ed., 2017, 56, 17 (a) T. Sperger, I. A. Sanhueza, I. Kalve and F. Schoenebeck,
52; (b) Q.-A. Chen, H. F. T. Klare and M. Oestreich, J. Am.
Chem. Soc., 2016, 138, 7868.
15 H.-J. Borschberg, Curr. Org. Chem., 2005, 9, 1465.
16 For computational details, see ESI, Section 7.†
Chem. Rev., 2015, 115, 9532; (b) C. Karmel and
J. F. Hartwig, J. Am. Chem. Soc., 2020, 142, 10494.
18 For details of 1H NMR, mass spectroscopy, infrared
spectrum and X-ray data of complexes 1bB and 3dB, see
ESI, Sections 6.1 and 8.†
© 2021 The Author(s). Published by the Royal Society of Chemistry
Chem. Sci., 2021, 12, 9748–9753 | 9753