Oligosilanes as Silyl Radical Precursors through Oxidative Si?Si Bond Cleavage Using Redox Catalysis

Article abstract of DOI:10.1002/anie.202011738

Oligosilanes are of great interest in the fields of organic photonics and electronics. In this communication, a highly efficient visible-light-mediated hydrosilylation of electron-deficient alkenes through cleavage of a trimethylsilyl-polysilanyl Si?Si bond is explored. These reactions smoothly occur on readily available organo(tristrimethylsilyl)silanes and other oligosilanes in the presence of an Ir^III-based photo-redox catalyst under visible light irradiation. Silyl radicals are generated through single electron oxidation of the oligosilane assisted by the solvent. The introduced method exhibits broad substrate scope and high functional group tolerance with respect to the organo(tristrimethylsilyl)silane and alkene components, enabling the construction of functionalized trisilanes. In addition, this catalytic system can be also applied to highly strained bicyclo[1.1.0]butanes as silyl radical acceptors.

Full text of DOI:10.1002/anie.202011738

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Accepted Article
Title: Oligosilanes as Silyl Radical Precursors through Oxidative Si−Si
Bond Cleavage using Redox Catalysis
Authors: Xiaoye Yu, Maximilian Lübbesmeyer, and Armido Studer
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.202011738
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Oligosilanes as Silyl Radical Precursors through Oxidative Si−Si
Bond Cleavage using Redox Catalysis
Xiaoye Yu, Maximilian Lꢀbbesmeyer, and Armido Studer*
Abstract: Oligosilanes are of great interest in the fields of organic
photonics and electronics. In this communication, a highly efficient
visible-light-mediated hydrosilylation of electron-deficient alkenes
through cleavage of a trimethylsilyl-polysilanyl Si−Si bond is explored.
relies on the reactive Si−H bond and derivatives therefrom are not
well investigated in synthesis.[9] Considering (TMS)3SiR (R = alkyl
and aryl[10]) as reagents, the Si−Si-bond will become the reactive
entity and the readily varied substituent R should allow tuning the
reactivity of such organotris(trimethylsilyl)silanes, which in turn
could greatly enrich available silanyl precursors (Scheme 1b).
Indeed, oligosilanes can undergo photolysis of a Si−Si bond,
albeit only under ultraviolet irradiation,[11] limiting the practical
application of this approach in synthesis. Other Si−Si bond-
breaking reactions in disilanes rely on the participation of a
transition metal complex,[12a] alkali and alkaline earth metal
salts[12b,c] or strong Brønsted acid[12d]. Therefore, the development
of a mild and practical method for Si−Si bond cleavage in
oligosilanes is still demanded.
These
reactions
smoothly
occur
on
readily
available
organo(tristrimethylsilyl)silanes and other oligosilanes in the presence
of an IrIII-based photo-redox catalyst under visible light irradiation. Silyl
radicals are generated through single electron oxidation of the
oligosilane assisted by the solvent. The introduced method exhibits
broad substrate scope and high functional group tolerance with
respect to the organo(tristrimethylsilyl)silane and alkene components,
enabling the construction of functionalized trisilanes. In addition, this
catalytic system can be also applied to highly strained
bicyclo[1.1.0]butanes as silyl radical acceptors.
Recently, visible-light-mediated photoredox catalysis[13] has
been successfully applied to silyl radical generation. Along these
lines, photo-mediated SET, HAT and energy transfer processes
have been developed starting with Si−H compounds.[14] In an
elegant study, Uchiyama and coworkers recently disclosed
photoinduced decarboxylation of silacarboxylic acids via a SET
process for silyl radical generation.[14d] Inspired by these works
and our interests in Si-radical chemistry,[15] we envisioned that
silyl radicals could be formed via oxidative trimethylsilyl-
polysilanyl bond cleavage under visible light irradiation using a
photocatalyst (PC) in a controlled way, enabling the radical
hydrosilylation of alkenes for the preparation of various 2,2-
difunctionalized trisilanes (Scheme 1c).
Oligosilanes are a class of compounds containing Si−Si bonds
that have attracted considerable attention given their unique
electronic and photophysical properties.[1] Early syntheses of
oligosilane derivatives which can be traced back to the 1920s
were achieved by reaction of dichlorodiphenylsilane with
sodium.[2] However, these compounds remained fairly unexplored
mainly due to their poor characterization until around 1975 when
polysilane homopolymers were started to be investigated in more
detail.[1a,3] Considering material properties, installation of
additional functionalities to the oligosilane backbone is of
importance. In this regard, oligosilanyl halides[3, 4] and oligosilanyl
hydrides[3] have been identified as substrates for modification of
oligosilanes through reductive couplings,[1a] Lewis acid-catalyzed
transformations[5], radical processes[6] or transition metal metal-
catalyzed reactions (Scheme 1a)[7]. However, these methods
show limited applicability due to their relatively harsh conditions
that lead to competing Si−Si bond cleavage. In this context, it is
highly desirable to develop synthetic methods which allow to
efficiently install diverse functional groups on the silicon backbone
in oligosilanes using readily available silanyl precursors.
As
a
special
class
of
oligosilanes,
organotris(trimethylsilyl)silanes have gained great interests over
the past decades and (TMS)3SiH as a commercially available
reagent has found particular attention.[6] (TMS)3SiH not only
serves as a radical chain reducing reagent in defunctionalizations,
but can also be used in hydrosilylations and as a mediator of other
radical reactions.[8] The chemistry of the parent (TMS)3SiH mainly
[a]
Dr. X. Yu, M. Lꢀbbesmeyer and Prof. Dr. A. Studer
Organisch-Chemisches Institut, Westfälische Wilhelms-Universität
Corrensstrasse 40, 48149 Münster (Germany)
E-mail: studer@uni-muenster.de
Scheme 1. Functionalization of oligosilanes.
Supporting information for this article is given via a link at the end of
the document.
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We commenced our study by exploring the hydrosilylation of
phenyltris(trimethylsilyl)silane (1a) with benzyl acrylate (2a, 1.5
equiv) under blue LED irradiation in the presence of a PC (1
mol%). MeOH was initially selected as the solvent (0.1 M) since it
should be able to assist the oxidative Si−Si -bond cleavage and
will further act as the proton donor. Upon using
[Ir(dF(CF3)ppy)2(dtbbpy)]PF6 as PC under blue LED irradiation
(30 W), the desired hydrosilylation product 3aa was formed, albeit
in a low yield (10%, Table 1, entry 1). Yield was slightly improved
upon switching to [Ir(dF(CF3)ppy)2(5,5'-d(CF3)bpy)]PF6 as the PC
yields. [c] 0.5 mL HFIP. [d] 3 mol% PC. [e] Ratio of 1a and 2a is 1:2. [f] degassing.
[g] Without visible light irradiation. [h] Without photocatalyst. bpy = 2,2’-bipyridyl.
ppy = 2-phenylpyridine. Bn = benzyl group. HFIP = 1,1,1,3,3,3-hexafluoro-2-
propanol. DMF = N,N-dimethylformamide.
With the optimal conditions identified, we next explored the
scope by reacting
a
range of differently substituted
tris(trimethylsilyl)silanes and benzyl acrylate on a 0.2 mmol scale
(Scheme 2). The reaction appears to be tolerant of various
aryltris-(trimethylsilyl)silanes. Along with 3aa, a series of aryltris-
(trimethylsilyl)silanes bearing electron-donating (Me, OMe) or
electron-withdrawing (F, CF3) groups at the para-position of the
phenyl ring gave good yields of the desired hydrosilylation
products 3ba-ea (59-73%). Moreover, meta-substituted
substrates were also compatible with the expected products 3fa
and 3ga being isolated in 70% and 58% yield, respectively. 2-
Naphthyltris-(trimethylsilyl)silane 1h reacted with 2a in acceptable
yield (3ha, 69%). Furthermore, commercially available
tetrakis(trimethylsilyl)silane 1i engaged in the reaction to provide
the corresponding product 3ia in good yield. However,
that is known to be a stronger oxidant in its excited state (EIII*/II
=
+1.30 V vs. Fc+/Fc in MeCN) (Table 1, entry 2-3).[16] We further
examined a series of solvents and as expected non-protic
solvents such as CHCl3, DMF and CH3CN provided worse results
(Table 1, entry 4-6). Pleasingly, HFIP proved more effective
delivering 3aa in 40% isolated yield (Table 1, entry 7).[16] The yield
could be further increased to 48% upon running the reaction at
higher concentration (Table 1, entry 8, 0.2 M). Next, photocatalyst
loading was increased (3 mol%) and a measurable improvement
was achieved (55%, Table 1, entry 9). 2 equivalents of the
acceptor 2a turned out to be optimal, affording 3aa with 65% yield
(Table 1, entry 10). Careful exclusion of air by freeze-pump-thaw
degassing further improved the result (72%, Table 1, entry 11).
Finally, control experiments demonstrated the necessity of each
of the key reaction components, and no product formation was
observed in the absence of either photocatalyst or light irradiation
(Table 1, entry 12 and 13).
Table 1. Reaction optimization.[a]
Entry
PC
Solvent
Yield [%][b]
1
[Ir(dF(CF3)ppy)2(dtbbpy)]PF6
[Ir(dF(CF3)ppy)2(5,5'-d(CF3)bpy)]PF6
[Ir(dF(CF3)ppy)2(bpy)]PF6
MeOH
MeOH
MeOH
CHCl3
DMF
10
2
26
3
23
4
5
[Ir(dF(CF3)ppy)2(5,5'-d(CF3)bpy)]PF6
[Ir(dF(CF3)ppy)2(5,5'-d(CF3)bpy)]PF6
[Ir(dF(CF3)ppy)2(5,5'-d(CF3)bpy)]PF6
[Ir(dF(CF3)ppy)2(5,5'-d(CF3)bpy)]PF6
[Ir(dF(CF3)ppy)2(5,5'-d(CF3)bpy)]PF6
[Ir(dF(CF3)ppy)2(5,5'-d(CF3)bpy)]PF6
[Ir(dF(CF3)ppy)2(5,5'-d(CF3)bpy)]PF6
[Ir(dF(CF3)ppy)2(5,5'-d(CF3)bpy)]PF6
[Ir(dF(CF3)ppy)2(5,5'-d(CF3)bpy)]PF6
[Ir(dF(CF3)ppy)2(5,5'-d(CF3)bpy)]PF6
trace
trace
6
CH3CN
HFIP
10
7
40
8[c]
HFIP
48
55
Scheme 2. Reaction of various oligosilanes with 2a. Conditions: 1 (0.2 mmol,
1.0 equiv), 2a (0.4 mmol, 2.0 equiv, 64.8 mg) and [Ir(dF(CF3)ppy)2(5,5'-
d(CF3)bpy)]PF6 (3 mol%) in HFIP (1 mL), rt, 24 h, degassing, 30 W blue LED.
Yields given correspond to isolated products. [a] Ratio of 1 and 2a is 2:1. bpy =
2,2’-bipyridyl. ppy = 2-phenylpyridine. Bn = benzyl group. HFIP = 1,1,1,3,3,3-
hexafluoro-2-propanol.
9[c,d]
HFIP
10[c,d,e]
11[c,d,e,f]
12[c,d,e,f,g]
13[c,d,e,f,h]
HFIP
65
HFIP
72
with hexakis(trimethylsilyl)disilane as the Si-radical precursor,
product 3ja was not observed and the starting persilylated disilane
could be recovered. Notably, when the ethyl substituted
tris(trimethylsilyl)silane was used, the corresponding product 3ka
was obtained with 50% yield showing that an aryl group at the
central silicon is not required. The O- and N-substituted
HFIP
No reaction
No reaction
HFIP
[a] Reaction conditions: 1a (0.10 mmol), 2a (0.15 mmol) and PC (1 mol%) in
solvent (1 mL) at rt under irradiation of 30 W blue LEDs for 12 h. [b] Isolated
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d(CF3)bpy)]PF6 (3 mol%) in HFIP (1 mL), rt, 24 h, degassing, 30 W blue LED.
Yields given correspond to isolated products. [a] Ratio of 1a and 2 is 2:1. bpy =
2,2’-bipyridyl. ppy = 2-phenylpyridine. Bn = benzyl group. HFIP = 1,1,1,3,3,3-
hexafluoro-2-propanol.
tris(trimethylsilyl)silanes 1l and 1m both provided product 3la in
20 and 30% yield, respectively. Since 1l and 1m turned out to be
stable toward HFIP, 3la was formed from the targeted products
by
reaction
with
HFIP.
Interestingly,
commercial
hexamethyldisilane could also be used as Me3Si-radical precursor
and 4 was isolated in 40% yield.
It is worth mentioning that vinyltris(trimethylsilyl)silane 1n
was applicable to this reaction when using dimethyl maleate 2l as
the acceptor, delivering the product 3nl with moderate yield
(Scheme 4a, 36%). Reaction of the nucleophilic Si-radical derived
from 1n occurred chemoselectively at the electrophilic double
bond of 2l and reaction with the benzyl acrylate 2a as acceptor
was not observed. In view of reactivity of the silyl radical with
respect to dehalogenation, we added 1 equivalent of n-hexyl
bromide or cyclohexyl bromide to the standard reaction conditions.
Under these conditions, only a trace amount of the product 3aa
was obtained with the starting phenyltris(trimethylsilyl)silane 1a
mostly remained unreacted. These experiments show that the Si-
radical derived from 1a preferably reacts with alkyl bromides
instead of engaging in the conjugate addition. Unfortunately, the
Giese-type addition of the alkyl bromides with 2a did not work
under these conditions, as checked by GCMS-analysis. To further
explore the potential of this methodology, we attempted to apply
our strategy to highly reactive bicyclo[1.1.0]butanes (BCBs) as Si-
radical acceptors.[17] Of note, radical additions to the central C−C
bond of BCBs are well established for the preparation of
functionalized cyclobutanes.[18] Gratifyingly, simple modification
of our optimized reaction conditions allowed the rapid access of
1,3-disubstituted cyclobutanes (see the Supporting Information
for optimization). As shown in Scheme 4b, BCBs bearing an
activating aryl sulfonyl substituent reacted with 1a to the
corresponding products 6a-c in good yields (50-61%) with 1:1-
diastereoselectivity.
We continued the studies by exploring the scope with respect
to the alkene component using 1a as the silyl donor (Scheme 3).
As expected, reaction worked with methyl acrylate (2b) to afford
3ab in 59% yield. Moreover, tert-butyl methacrylate (2c), phenyl
methacrylate (2d) and the γ-butyrolactone 2e were found to be
effective acceptors to give the desired products 3ac-ae in good
yields. 2-Aryl acrylates bearing different substituents at the aryl
group (H, OMe, Cl) engaged in the cascade to furnish 3af-ah in
moderate to good yields (55-78%). However, phenyl vinyl ketone
(2i) provided a significantly lower yield (3ai, 46%). Gratifyingly,
when a methyl group was introduced into the β-position of 2i,
reaction proceeded well to deliver 3aj in good yield (74%). The
hydrosilylation was successfully applied to the cyclic enone 2k
(3ak, 51%). Other electron-deficient alkenes such as dimethyl
maleate (2l), fumaronitrile (2m), acrylamide 2n and the vinyl
sulfone 2o were eligible acceptors to afford the corresponding
hydrosilylation products 3al-ao in 50-73% yield. It should be noted
that electron-deficient styrene derivatives 2p and 2q engaged in
this transformation, albeit products 3ap and 3aq were isolated in
low yields and a large amount of starting materials remained
unreacted. For styrene, only traces of product were identified.
Hence, reaction only works for styrene derivatives leading to
electrophilic-type benzylic radicals. Indeed, 2-vinylpyridine 2r
provided 3ar in 70% isolated yield.
Finally, we could show that the trisilane products can act as
silyl donors in a renewed redox neutral hydrosilylation. This was
documented by the reaction of trisilane 3am with 2a under our
standard conditions which afforded the disilane 7 in moderate
yield (Scheme 4c).
Scheme 4. Synthetic utility. a) Reaction condition: 1n (0.4 mmol, 2.0 equiv), 2l
(0.2 mmol, 1.0 equiv) and [Ir(dF(CF3)ppy)2(5,5'-d(CF3)bpy)]PF6 (3 mol%) in
HFIP (1 mL), rt, 24 h, degassing, 30 W blue LED. b) Reaction condition: 1a (0.15
Scheme 3. Reaction of 1a with various alkenes. Conditions: 1a (0.2 mmol, 1.0
equiv, 65.0 mg),
2 (0.4 mmol, 2.0 equiv) and [Ir(dF(CF3)ppy)2(5,5'-
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mmol, 1.0 equiv, 48.7 mg), 5 (0.1 mmol, 1.0 equiv), H2O (1.0 mmol, 10 equiv)
and [Ir(dF(CF3)ppy)2(5,5'-d(CF3)bpy)]PF6 (3 mol%) in CH3CN (0.5 mL), rt, 24 h,
degassing, 6 W blue LED. dr = 1:1. c) Reaction condition: 3am (0.2 mmol, 2.0
equiv, 65.0 mg), 2a (0.1 mmol, 1.0 equiv) and [Ir(dF(CF3)ppy)2(5,5'-
d(CF3)bpy)]PF6 (3 mol%) in HFIP (0.5 mL), rt, 24 h, degassing, 30 W blue LED.
To gain insights into the mechanism, some additional
experiments were carried out. Formation of product 3aa was
largely suppressed in the presence of TEMPO (Scheme 5a).
Stern−Volmer
quenching
experiments
revealed
that
phenyltris(trimethylsilyl)silane 1a with the assistance of HFIP
could efficiently quench the excited photocatalyst while substrate
2a did not quench the excited state of the photocatalyst. The
importance of HFIP for oxidation of 1a was supported by the fact
that no quenching of the excited photocatalyst was observed with
1a in CH3CN. Moreover, for 1b bearing the electron-donating
para-methyl group a small decrease in the emission intensity was
measured as compared to the parent 1a. The para-fluoro
substituent (see 1d) did not show a large effect and a similar
quenching efficiency as with 1a was measured. These results are
in accordance with cyclic voltammetry experiments. The
tris(trimethylsilyl)silanes 1a, 1b, and 1d are irreversibly oxidized
anodically. The oxidation is observed as a superposition of two
consecutive oxidation processes. The first process that is relevant
in the context of this study is observed at peak potentials of
approx. 1.0 V, 0.9 V, and 1.1 V versus Fc/Fc+ in HFIP,
respectively, reflecting the electronic characteristics of the phenyl
substituents (see SI for detailed information). In contrast, a
significantly higher peak potential of approx. 1.4 V versus Fc/Fc+
was determined for 1a in CH3CN. Oxidation of the
tris(trimethylsilyl)silanes by the excited state photocatalyst
(EIr(II)/*Ir(III) = 1.30 V versus Fc/Fc+ in CH3CN)[19a] is, thus,
thermodynamically favored in HFIP only.
Scheme 5. Proposed mechanism.
In summary, we have utilized organo(tristrimethylsilyl)silanes
as silyl radical precursors in redox neutral hydrosilylation of
electron-deficient alkenes. Diversely substituted silyl radicals are
generated as key intermediates through direct activation of a
trimethylsilyl-polysilanyl Si−Si bond via single electron oxidation,
enabling rapid access to a wide range of functionalized trisilanes.
Along with electron-poor alkenes, strained bicyclo[1.1.0]butanes
also react as Si-radical acceptors. Notably, sequential double
hydrosilylation starting with aryl(tristrimethylsilyl)silanes is also
feasible. Considering the broad substrate scope and operationally
simple procedure the introduced methodology should find
widespread use for the preparation of functionalized oligosilanes.
Based on these results and the fact that both light and
photocatalyst are required, we propose a mechanism that is
presented in Scheme 5b, exemplified for the reaction with 1a. The
catalytic cycle starts with SET oxidation of 1a by the excited state
photocatalyst *Ir(III), forming the silyl radical 1a-I and the
corresponding reduced Ir(II)-complex. Si-radical generation is
likely mediated by HFIP to give Me3SiOCH(CF3)2 which is
identified as a byproduct. The free Si-radical 1a-I then adds to the
double bond of 2, generating the adduct carbon radical 1a-II.
Reduction of 1a-II by the Ir(II)-complex gives the anion 1a-III with
concomitant regeneration of the ground-state Ir(III)-complex,[19b]
closing the photocatalytic cycle. As expected, reduction is only
possible for electrophilic type radicals 1a-II. This is well reflected
by the styrene series where only the electron-poor pyridine
derivative provided a high yield, whereas the parent styrene did
not work. Protonation of 1a-III eventually affords the final product
3.
Acknowledgements
We thank the WWU Mꢀnster and Alexander von Humboldt
foundation (postdoctoral fellowship to X.Y.) for financial support.
Keywords: oligosilanes • photocatalysis • single-electron
transfer • silyl radicals • hydrosilylation
[1]
For reviews, see: a) R. D. Miller, J. Michl, Chem. Rev. 1989, 89, 1359; b)
R. West, J. Organomet. Chem. 1986, 300, 327; c) M. Fujiki, Macromol.
Rapid Commun. 2001, 22, 539. For selective examples: c) I. El-Sayed,
Y. Hatanaka, C. Muguruma, S. Shimada, M. Tanaka, N. Koga, M. Mikami,
J. Am. Chem. Soc. 1999, 121, 5095; d) K. Tamao, H. Tsuji, M. Terada,
M. Asahara, S. Yamaguchi, A. Toshimitsu, Angew. Chem. Int. Ed. 2000,
39, 3287; Angew. Chem. 2000, 112, 3425.
[2]
[3]
a) F. S. Kipping, J. Chem. Soc. 1921, 119, 830; b) F. S. Kipping, J. Chem.
Soc. 1924, 125, 2291.
a) C. Marschner, Oligosilanes. In Functional Molecular Silicon
Compounds I: Regular Oxidation States; D. Scheschkewitz, Ed.;
Springer: Cham, Switzerland, 2014, 163; b) C. Chatgilialoglu, Chem. Rev.
1995, 95, 1229; c) E. Rivard, Chem. Soc. Rev. 2016, 45, 989.
For selected examples, see: a) K. Kanno, Y. Aikawa, Y. Niwayaman, M.
Ino, K. Kawamura, S. Kyushin, Inorganics 2018, 6, 99; b) C. Ackerhans,
H. W. Roesky, D. Vidovic, J. Magull, Eur. J. Inorg. Chem. 2003, 66; c) B.
Wrackmeyer, W. Milius, A. Badshah, J. Organomet. Chem. 2002, 656,
[4]
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COMMUNICATION
97; d) U. Böhme, B. Günther, B. Rittmeister, Eur. J. Inorg. Chem. 2003,
1946; i) D. C. Fabry, M. Rueping, Acc. Chem. Res. 2016, 49, 1969;
j) O. Reiser, Acc. Chem. Res. 2016, 49, 1990; k) M. N. Hopkinson, A.
Tlahuext-Aca, F. Glorius, Acc. Chem. Res. 2016, 49, 2261; l) M. D.
Kärkäs, J. A. Porco, C. R. J. Stephenson, Chem. Rev. 2016, 116, 9683;
m) K. L. Skubi, T. R. Blum, T. P. Yoon, Chem. Rev. 2016, 116, 10035; n)
N. A. Romero, D. A. Nicewicz, Chem. Rev. 2016, 116, 10075; o) D.
Cambié, C. Bottecchia, N. J. W. Straathof, V. Hessel, T. Noël, Chem.
Rev. 2016, 116, 10276; p) B. Chen, L.-Z. Wu, C.-H. Tung, Acc. Chem.
Res. 2018, 51, 2512; q) M. Silvi, P. Melchiorre, Nature 2018, 554, 41; r)
L. Marzo, S. K. Pagire, O. Reiser, B. König, Angew. Chem. Int. Ed. 2018,
57, 10034; Angew. Chem. 2018, 130, 10188.
751.
[5]
For selected examples, see: a) D. J. Harrison, R. McDonald, L.
Rosenberg, Organometallics 2005, 24, 1398; b) N. Kato, Y. Tamura, T.
Kashiwabara, T. Sanji, M. Tanaka, Organometallics 2010, 29, 5274; c)
M. K. Skjel, A. Y. Houghton, A. E. Kirby, D. J. Harrison, R. McDonald, L.
Rosenberg, Org. Lett. 2010, 12, 376.
[6]
[7]
[8]
a) C. Chatgilialoglu, Chem. Eur. J. 2008, 14, 2310; b) C. Chatgilialoglu,
Molecules 2012, 17, 527; c) C. Chatgilialoglu, C. Ferreri, Y. Landais, V.
I. Timokhin, Chem. Rev. 2018, 118, 6516.
For reviews, see: a) K. A. Horn, Chem. Rev. 1995, 95, 1317; b) H. K.
Sharma, K. H. Pannell, Chem. Rev. 1995, 95, 1351; c) I. Beletskaya,
Chem. Rev. 2006, 106, 2320.
[14] a) J.-S. Li, J. Wu, ChemPhotoChem 2018, 2, 839; for selected examples,
see: b) R. Zhou, Y. Y. Goh, H. Liu, H. Tao, L. Li, J. Wu, Angew. Chem.
Int. Ed. 2017, 56, 16621; Angew. Chem. 2017, 129, 16848; c) J. Hou, A.
Ee, H. Cao, H.-W. Ong, J.-H. Xu, J. Wu, Angew. Chem. Int. Ed. 2018, 57,
17220; Angew. Chem. 2018, 130, 17466; d) N.-X. Xu, B.-X. Li, C. Wang,
M. Uchiyama, Angew. Chem. Int. Ed. 2020, 59, 10639; Angew. Chem.
2020, 132, 10726. For selected examples about silyl radicals formation
from silanols, see: e) C. Le, T. Q. Chen, T. Liang, P. Zhang, D. W. C.
MacMillan, Science 2018, 360, 1010; f) M. Shee, S. S. Shah, N. D. P.
Singh, Chem. Commun. 2020, 56, 4240.
For selected examples, see: a) B. Kopping, C. Chatgilialoglu, M. Zehnder,
B. Giese, J. Org. Chem. 1992, 57, 14, 3994; b) P. Zhang, C. C. Le, D. W.
C. MacMillan, J. Am. Chem. Soc. 2016, 138, 8084; c) T. Kerackian, A.
Reina, D. Bouyssi, N. Monteiro, A. Amgoune, Org. Lett. 2020, 22, 2240;
d) S. M. Hell, C. F. Meyer, G. Laudadio, A. Misale, M. C. Willis, T. Noꢁl,
A. A. Trabanco, V. Gouverneur, J. Am. Chem. Soc. 2020, 142, 720.
H. A. Sakai, W. Liu, C. Le, D. W. C. MacMillan, J. Am. Chem. Soc. 2020,
142, 11691.
[9]
[10] a) C. Marschner, Eur. J. Inorg. Chem. 1998, 221; b) M. Bochmann, M. L.
H. Green, A. K. Powell, J. Sassmannshausen, M. U. Triller, S. Wocadlo,
J. Chem. Soc. Dalton Trans. 1 1999, 43. c) M. J. Sanganee, P. G. Steel,
D. K. Whelligan, J. Org. Chem. 2003, 68, 3337.
[15] a) A. Studer, S. Amrein, Angew. Chem. Int. Ed. 2000, 39, 3080; Angew.
Chem. 2000, 112, 3196; b) S. Amrein, A. Timmermann, A. Studer, Org.
Lett. 2001, 3, 2357; c) S. Amrein, A. Studer Chem. Commun. 2002,
1592; d) A. Studer, S. Amrein, F. Schleth, T. Schulte, J. C. Walton, J. Am.
Chem. Soc. 2003, 125, 5726.
[11] a) M. Ishikawa, K. Nakagawa, S. Katayama, M. Kumada, J. Am. Chem.
Soc. 1981, 103, 4170; b) T. Kusukawa, W. Ando, Organometallics 1997,
16, 4027; c) G. W. Sluggett, W. J. Leigh, Organometallics 1992, 11, 3731;
d) G. W. Sluggett, W. J. Leigh, J. Am. Chem. Soc. 1992, 114, 1195; e)
W. J. Leigh, G. W. Sluggett, Organometallics 1994, 13, 269; f) M. Kira,
K. Sakamoto, H. Sakurai, J. Am. Chem. Soc. 1983, 105, 7469; g) H.
Sakurai, K. Sakamoto, M. Kira, Chem. Lett. 1984, 1213; h) Y. Nakadaira,
N. Komatsu, H. Sakurai, Chem. Lett. 1985, 1781.
[16] See the Supporting Information for more detail.
[17] a) K. B. Wiberg, G. M. Lampman, R. P. Ciula, D. S. Connor, P.Schertler,
J. Lavanish, Tetrahedron 1965, 21, 2749; b) T. Seiser, T. Saget, D. N.
Tran, N. Cramer, Angew. Chem. Int. Ed. 2011, 50, 7740; Angew. Chem.
2011, 123, 7884.
[18] a) X.-Y. Yu, J.-R. Chen, W.-J. Xiao, Chem. Rev. 2020, DOI:
10.1021/acs.chemrev.0c00030. For selected examples, see: b) R.
Gianatassio, J. M. Lopchuk, J. Wang, C.-M. Pan, L. R. Malins, L. Prieto,
T. A. Brandt, M. R. Collins, G. M. Gallego, N. W. Sach, J. E. Spangler, H.
Zhu, J. Zhu, P. S. Baran, Science 2016, 351, 241; c) J. M. Lopchuk, K.
Fjelbye, Y. Kawamata, L. R. Malins, C.-M. Pan, R. Gianatassio, J. Wang,
L. Prieto, J. Bradow, T. A. Brandt, M. R. Collins, J. Eleraas, J. Ewanicki,
W. Farrell, W. Farrell, O. O. Fadeyi, G. M. Gallego, J. J. Mousseau, P.
Olivier, N. W. Sach, J. K. Smith, J. E. Spangler, H. Zhu, J. Zhu, P. S.
Baran, J. Am. Chem. Soc. 2017, 139, 3209; d) G. Ernouf, E. Chirkin, L.
Rhyman, P. Ramasami, J. C. Cintrat, Angew. Chem. Int. Ed. 2020, 59,
2618; Angew. Chem. 2020, 132, 2640.
[12] a) A. Lu, X. Ji, B. Zhou, Z. Wu, Y. Zhang, Angew. Chem. Int. Ed. 2018,
57, 3233; Angew. Chem. 2018, 130, 3287; b) X. Wang, M.-H. Zhu, D. P.
Schuman, D. Zhong, W.-Y. Wang, L.-Y. Wu, W. Liu, B. M. Stoltz, W.-B.
Liu, J. Am. Chem. Soc. 2018, 140, 10970; c) T. Santowski, A. G. Sturm,
K. M. Lewis, T. Felder, M. C. Holthausen, N. Auner, Chem. Eur.J. 2019,
25,13202; d) Q. Wu, A. Roy, E. Irran, Z.-W. Qu, S. Grimme, H. F. T. Klare,
M. Oestreich, Angew. Chem. Int. Ed. 2019, 58, 17307; Angew. Chem.
2019, 131, 17468.
[13] a) J. Xuan, W.-J. Xiao, Angew. Chem. Int. Ed. 2012, 51, 6828; Angew.
Chem. 2012, 124, 6934; b) C. K. Prier, D. A. Rankic, D. W. C. MacMillan,
Chem. Rev. 2013, 113, 5322; c) J. C. Tellis, C. B. Kelly, D. N. Primer, M.
Jouffroy, N. R. Patel, G. A. Molander, Acc. Chem. Res. 2016, 49, 1429;
d) E. C. Gentry, R. R. Knowles, Acc. Chem. Res. 2016, 49, 1546; e) I.
Ghosh, L. Marzo, A. Das, R. Shaikh, B. König, Acc. Chem. Res. 2016,
49, 1566; f) J.-R. Chen, X.-Q. Hu, L.-Q. Lu, W.-J. Xiao, Acc. Chem. Res.
2016, 49, 1911; g) T. Koike, M. Akita, Acc. Chem. Res. 2016, 49, 1937;
h) K. Nakajima, Y. Miyake, Y. Nishibayashi, Acc. Chem. Res. 2016, 49,
[19] a) G. J. Choi, Q. Zhu, D. C. Miller, C. J. Gu, R. R. Knowles, Nature 2016,
539, 268. b) Gennaro et al. determined the reduction potentials of
•
•CH2CO2Et and CH(CH3)CO2Me as −0.63 V and −0.66 V versus SCE;
see N. Bortolamei, A. A. Isse, A. Gennaro, Electrochimica Acta 2010, 55,
8312. Reduction of 1a-II by the Ir(II) complex (EIr(II)/Ir(III) = −0.69 V versus
SCE, see [19a]) is, thus, reasonable.
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Oligosilanes as Silyl Radical
Precursors through Oxidative Si−Si
Bond Cleavage using Redox
Catalysis
Radical hydrosilylation of electron-deficient alkenes through cleavage of
a
trimethylsilyl-polysilanyl bond has been accomplished. These reactions smoothly
occur by direct activation of a trimethylsilyl-polysilanyl bond via single electron
oxidation by a redox catalyst assisted by solvent under visible light irradiation. This
catalytic strategy could be also applied to the silylation of highly strained
bicyclo[1.1.0]butanes.
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