Categories: C-Si Bond Formation > Silanes
Synthesis of alkylsilanes
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Organofluorophosphonium salts exhibit Lewis acidity derived from a low-lying σ*
orbital at P opposite F. Due to the acidity, these salts for example catalyze
the rapid isomerization of 1-hexene to 2-hexene and a cationic polymerization of
isobutylene. In the presence of hydrosilanes and a catalytic amount of an
organofluorophosphonium salt, olefins and alkynes undergo efficient
hydrosilylation.
M. Pérez, L. J. Hounjet, C. B. Caputo, R. Dobrovetsky, D. W. Stephan, J. Am. Chem. Soc., 2013,
135, 18308-18310.
Using triethylborane as the initiator, phenyldimethylsilane and trichlorosilane
undergo efficient radical hydrosilylation reactions with various alkenes.
Adducts from the trichlorosilane reactions can be oxidised to afford alcohols in
moderate yields. This two-step process leads to the anti-Markovnikov
hydration of alkenes.
M. J. Palframan, A. F. Parsons, P. Johnson, Synlett, 2011,
2811-2814.
The combination of NiCl2·6H2O/tBuOK catalyzes an
electrophilically activated hydrosilylation of terminal alkenes with primary
silanes under mild reaction conditions with excellent performance, exclusive
anti-Markovnikov selectivity, broad functional group tolerance, and good
scalability. However, secondary and tertiary silanes are not suitable.
X. Wu, G. Ding, W. Lu, L. Yang, J. Wang, Y. Zhang, X. Xie, Z. Zhang, Org. Lett., 2021, 23,
1434-1439.
Gaseous and flammable silanes are inconvenient to use in chemical reactions.
Catalytic amounts of a nickel pincer complex and NaOtBu enable the
synthesis of alkyl hydrosilanes from alkenes and alkoxy hydrosilanes. The scope
and mechanism of the hydrosilylation reactions are also described.
I. Buslov, S. C. Keller, X. Hu, Org. Lett., 2016, 18,
1928-1931.
An iron-catalyzed highly Markovnikov-type selective and enantioselective
hydrosilylation of terminal aliphatic alkenes with good functional group
tolerance provides valuable chiral organosilanes with high ees. Chiral aliphatic
alkan-2-ols could be efficiently synthesized via further derivatization of
chiral organosilanes without any racemization.
B. Cheng, W. Liu, Z. Lu, J. Am. Chem. Soc.,
2018,
140, 5014-5017.
Pincer iron complexes with electron-donating phosphinite-iminopyridine (PNN)
ligands are efficient catalysts for the anti-Markovnikov alkene hydrosilylation
of primary, secondary, and tertiary silanes. More importantly, the system
tolerates reactive groups such as ketones, esters, and amides. Furthermore, the
iron catalysts may provide a low-cost and environmentally benign alternative to
currently employed systems for alkene hydrosilylation.
D. Peng, Y. Zhang, X. Du, L. Zhang, X. Leng, M. D. Walter, Z. Huang, J. Am. Chem. Soc., 2013,
135, 19154-19166.
A Co catalyst for anti-Markovnikov alkene hydrosilylation can be generated in
situ from an air-stable precursor that is simple to synthesize from low-cost,
commercially available materials. This inexpensive catalyst can be used without
added solvent at low temperatures with low loadings. In addition, a mixture of
Co catalysts performs a tandem catalytic alkene isomerization/hydrosilylation
reaction.
C. Chen, M. B. Hecht, A. Kavara, W. W. Brennessel, B. Q. Mercado, D. J. Weix, P.
L. Holland, J. Am. Chem. Soc., 2015,
137, 13244-13247.
Gold nanoparticles supported on ZrO2 efficiently generate alkyl
radicals via homolysis of unactivated C(sp3)-O bonds. A subsequent
C(sp3)-Si bond formation provides diverse organosilicon compounds. A
wide array of esters and ethers participated in the heterogeneous gold-catalyzed
silylation by disilanes to give diverse alkyl-, allyl-, benzyl-, and allenyl
silanes in high yields.
H. Miura, M. Doi, Y. Yasui, Y. Masaki, H. Nishio, T. Shishido, J. Am. Chem. Soc.,
2023, 145, 4613-4625.
The reaction of unactivated secondary and primary alkyl chlorides as well as
primary alkyl triflates with silyl lithium reagents provides tetraorganosilanes
in good yields in the absence of any transition metal catalyst under mild
conditions. The silyl lithium reagents are readily generated from the
corresponding commercially available chlorosilanes.
S. Mallick, E.-U. Würthwein, A. Studer,
Org. Lett., 2020, 22, 6568-6572.
A zinc-catalyzed nucleophilic substitution reaction of chlorosilanes with
organomagnesium reagents affords a broad range of functionalized
tetraorganosilanes under mild reaction conditions. The reaction can be performed
on large scale.
K. Murakami, H. Yorimitsu, K. Oshima, J. Org. Chem., 2009,
74, 1415-1417.
Palladium-Catalyzed Cross-Coupling of Silyl Electrophiles with Alkylzinc
Halides: A Silyl-Negishi Reaction
A. P. Cinderella, B. Vulovic, D. A. Watson, J. Am. Chem. Soc., 2017,
139, 7741-7744.
Various siletanes have been used as substrates for the oxidation of
carbon-silicon bonds upon exposure to aqueous fluoride and peroxide. These
tetraalkylsilanes offer a combination of stability and reactivity with many
practical benefits, including compatibility with silicon protecting groups
and electron-rich aromatic rings.
J. D. Sunderhaus, H. Lam, G. B. Dudley, Org. Lett.,
2003, 8, 4571-4573.
In a nucleophilic displacement of the triflate leaving group attached to
terminally functionalized alkyl groups, copper catalysis is used to release the
silicon nucleophile from Suginome's Si-B reagent. The functional group tolerance
is excellent, the reaction even tolerates halide leaving groups.
J. Scharfbier, M. Oestreich,
Synlett, 2016, 27, 1274-1276.
A simple, commercially available nickel catalyst (NiBr2·diglyme) can
achieve couplings of unactivated alkyl bromides with nucleophilic silicon
reagents under unusually mild conditions.
C. K. Chu, Y. Liang, G. C. Fu, J. Am. Chem. Soc., 2016,
138, 6404-6407.
A C(sp3)-Si coupling of unactivated alkyl bromides with vinyl
chlorosilanes proceeds under mild conditions to provide alkylsilanes.
Functionalities such as Grignard-sensitive groups (e.g., acid, amide, alcohol,
ketone, and ester), acid-sensitive groups (e.g., ketal and THP protection),
alkyl fluoride and chloride, aryl bromide, alkyl tosylate and mesylate, silyl
ether, and amine were tolerated.
J. Duan, Y. Wang, L. Qi, P. Guo, X. Pang, X.-Z. Shu, Org. Lett., 2021, 23,
7855-7859.
A cobalt-catalyzed enantioselective hydrosilylation of terminal alkenes enables
an efficient synthesis of valuable chiral dihydrosilanes. This protocol is
operationally simple and atom-economic using relatively simple and readily
available starting materials.
B. Cheng, P. Lu, H. Zhang, X. Cheng, Z. Lu, J. Am. Chem. Soc., 2017,
139, 9439-9442.
Phosphonium salts catalyze a coupling of both activated and nonactivated alkyl
halides with both trichlorosilane and methyldichlorosilane. A wide variety of
silyl-functionalized compounds may be prepared easily and in good yields.
Y. S. Cho, S.-H. Kang, J. S. Han, B. R. Yoo, I. N. Jung, J. Am. Chem. Soc., 2001,
123, 5584-5585.
Allylsilylation allows to install both silyl and allyl groups onto a
carbon-carbon double bond directly. Proton-exchanged montmorillonite showed
excellent catalytic performances for the allylsilylation of alkenes. Isolation
of the reaction intermediate on the montmorillonite surface helped to
investigate the reaction mechanism.
K. Motokura, S. Matsunaga, A. Miyaji, Y. Sakamoto, T. Baba, Org. Lett., 2010,
12, 1508-1511.
Electroreduction of readily available chlorosilanes enables a new strategy
for silyl radical generation via energetically uphill reductive cleavage of
strong Si-Cl bonds at highly biased potentials. This convenient and
transition-metal-free strategy proved to be general in various alkene silylation
reactions including disilylation, hydrosilylation, and allylic silylation.
L. Lu, J. C. Siu, Y. Lai, S. Lin, J. Am. Chem. Soc.,
2020, 142, 20979-20986.
A water-insoluble copper(II) acetylacetonate-chiral bipyridine complex catalyzed
an asymmetric silyl conjugate addition of lipophilic substrates in water. Indeed,
the reactions proceeded efficiently only in water. Water seems to play a role in
constructing and stabilizing sterically confined transition states and
accelerating subsequent protonation.
T. Kitanosono, L. Zhu, C. Liu, P. Xu, S. Kobayashi, J. Am. Chem. Soc., 2015,
137, 15422-15425.
Irradiating 3-silyl-1,4-cyclohexadienes with blue light in the presence of a
commercially available photocatalyst smoothly generated silyl radicals bearing
various substituents. A subsequent trapping by a broad range of alkenes affords
products in good yields within 1 h. This photoredox-induced homolysis enables also an efficient
generation of germyl radicals.
B.-X. Li, H. Ishida, C. Wang, M. Uchiyama, Org. Lett., 2023, 25,
1765-1770.
The use of Martin's spirosilane-derived pentacoordinate silylsilicates as silyl
radical precursors enables a visible-light-induced hydrosilylation of a broad
range of alkenes and alkynes, as well as the C-H silylation of heteroarenes.
Remarkably, Martin’s spirosilanes were stable and could be recovered via a
simple workup process.
Y. Zhao, Y. Wan, Q. Yuan, J. Wei, Y. Zhang, Org. Lett., 2023, 25,
1386-1391.
The presence of a catalytic amount of copper(II) and an amine base enables a
mild method for the installation of the dimethylphenylsilyl group on the
β-carbon of electron-deficient olefins at rt. The transformation proceeds
efficiently in water within 1.5–5 h to afford β-silylated products in good
yields.
J. A. Calderone, W. L. Santos, Org. Lett., 2012,
14, 2090-2093.
A rhodium-catalyzed enantioselective hydrosilylation of unactivated internal
alkenes bearing a polar amide group for coordination assistance provides silanes
with high regio- and enantioselectivity.
W-R. Zhang, W.-W. Zhang, H. Li, B.-J. Li, Org. Lett., 2023, 25,
1667-1672.
Supported Au nanoparticles on TiO2 catalyze the insertion of carbenes
from α-diazocabonyl compounds into hydrosilanes without ligands or additives.
This purely heterogeneous process allows the recycling and reuse of the catalyst.
M. Kidonakis, M. Stratakis, Org. Lett.,
2018, 20, 4086-4089.
A chiral spiro-bisoxazoline ligand has proven to be an optimal ligand for an
asymmetric iron-catalyzed enantioselective Si-H bond insertion reaction of
α-diazoesters to provide chiral α-silyl esters in good yields with high
enantioselectivities. The reaction proceeds via a concerted quintet transition
state.
H. Gu, Z. Han, H. Xie, X. Lin, Org. Lett.,
2018, 20, 6544-6549.
An efficient copper-catalyzed carbenoid insertion reaction of α-diazo carbonyl
compounds into Si-H and S-H bonds provides a broad range of α-silylesters and
α-thioesters in high yields using 5 mol% of a simple copper(I) salt as catalyst.
In addition, α-diazoketones can be converted to α-silylketones in moderate
yields.
H. Keipour, A. Jalba, L. Delage-Laurin, T. Ollevier, J. Org. Chem.,
2017, 82, 3000-3010.
An efficient carbene insertion reaction of α-diazoesters into Si-H bond
provides a wide range of α-silylesters in high yields using a simple iron(II)
salt as catalyst.
H. Keipour, T. Ollevier, Org. Lett.,
2017, 19, 5736-5739.
In the presence of cationic rhodium complexes, Si-B compounds function as equivalents of nucleophilic silicon, which is
efficiently transferred onto acyclic as well as cyclic α,β-unsaturated carbonyl
compounds. [((S)-binap)Rh(cod)]ClO4 has effected an asymmetric
1,4-addition to cyclic acceptors in high enantiomeric excess.
C. Walter, G. Auer, M. Oestreich, Angew. Chem. Int. Ed., 2006, 45, 5675-5677.
A convenient method for the synthesis of 1,1-diboronates from the corresponding
N-tosylhydrazones is also applicable to 1-silyl-1-boron compounds.
Derivatization and consecutive Pd-catalyzed cross-coupling reactions with
1,1-boronates were also explored, demonstrating the synthetic potential of
1,1-diboronates.
H. Li, X. Shangguan, Z. Zhang, S. Huang, Y. Zhang, J. Wang, Org. Lett., 2014,
16, 448-451.
A platinum-catalyzed intramolecular silaboration of borylsilanyl homoallyl
ethers gave 1-oxa-2-silacyclopentanes in high yields. The stereoselectivity of
the reactions strongly depended on the used ligands. A complementary synthesis
of a pair of diastereomers of 6-methylheptane-1,3,5-triol is described.
T. Ohmura, H. Furukawa, M. Suginome, J. Am. Chem. Soc., 2006, 128, 13366-13367.
T. Ohmura, H. Furukawa, M. Suginome, J. Am. Chem. Soc., 2006, 128, 13366-13367.
Highly efficient, stereo- and regioselective palladium-catalyzed
hydro-, sila-, and stannastannations of cyclopropenes gave multisubstituted
cyclopropylstannanes. The addition across
the double bond proceeds from the least hindered face.
M. Rubina, M. Rubin, V. Gevorgyan, J. Am. Chem. Soc., 2002, 124, 11566-11567.