Dual Palladium/Copper-Catalyzed anti-Selective Intermolecular Allenylsilylation of Terminal Alkynes: Entry to (E)-Silyl Enallenes

Article abstract of DOI:10.1021/acs.orglett.1c02364

A palladium-/copper-cocatalyzed three-component trans-allenylsilylation of terminal alkynes with propargyl acetates and PhMe2SiBpin is described, which is driven by the regioselective allenylation of the alkyne with propargyl acetates and then silylation. This method allows the simultaneous incorporation of an allene and silicon across the CC bond and provides a highly chemo-, regio-, and stereoselective alkyne difunctionalization route to the synthesis of valuable (E)-silyl enallenes. The utility of this method is highlighted by late-stage derivatization of bioactive compounds.

Full text of DOI:10.1021/acs.orglett.1c02364

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Letter
Dual Palladium/Copper-Catalyzed anti-Selective Intermolecular
Allenylsilylation of Terminal Alkynes: Entry to (E)‑Silyl Enallenes
Liang-Feng Yang, Qiu-An Wang,* and Jin-Heng Li*
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ABSTRACT: A palladium-/copper-cocatalyzed three-component trans-allenylsilylation of terminal alkynes with propargyl acetates
and PhMe2SiBpin is described, which is driven by the regioselective allenylation of the alkyne with propargyl acetates and then
silylation. This method allows the simultaneous incorporation of an allene and silicon across the CC bond and provides a highly
chemo-, regio-, and stereoselective alkyne difunctionalization route to the synthesis of valuable (E)-silyl enallenes. The utility of this
method is highlighted by late-stage derivatization of bioactive compounds.
Scheme 1. Carbosilylation of Alkynes
he alkene difunctionalization reaction is among the most
powerful methodologies to economically and rapidly
T
synthesize complex alkene-based structures from readily
available feedstocks in synthesis.1,2 Particularly, those reactions
that execute intermolecular difunctionalization of alkynes have
additional important values because they can bond the seams
of three components together in the desired combinations to
create CC bond networks and exquisitely control the
stereo-, regio-, and chemoselectivity.1,2 Typically, the selective
silyl-carbofunctionalization of alkynes that consists of silylation
of alkynes with organosilicon reagents followed by carbofunc-
tionalization with carbon donor reagents is attractive and can
offer an innovative solution to access versatile vin-2-ylsilane
scaffolds, thereby providing the potential to further orient
derivatization and increase structural diversity.2−5 Since Pastor
pioneered a Rh4(CO)12-catalyzed silylformylation of alkynes
with Me2PhSiH and CO (10−30 kg/cm2) in 1989,3a
transition-metal-catalyzed carbosilylation of alkynes with
trisubstituted silanes and carbon donors (such as high-pressure
CO and alkyl isocyanides) has been well investigated for
constructing various functionalized vinylsilanes, mainly
through initially manipulating the regioselective silylation of
alkynes and then carbofunctionalization (Scheme 1a).2,3
However, these approaches suffer from unsatisfactory stereo-
selectivity with a mixture of Z and E isomers and narrow
carbon donors. To achieve high stereoselectivity, Murai and
co-workers have developed a Pd(PPh3)4 catalysis that uses a
combination of trisubstituted silyl iodide electrophiles and
organometallic nucleophiles (such as organotin and organozinc
reagents) to accomplish the syn-selective silyl-carbofunctional-
ization of terminal alkynes (Scheme 1b,c).4a,b Very recently,
Received: July 15, 2021
Published: August 10, 2021
https://doi.org/10.1021/acs.orglett.1c02364
Org. Lett. 2021, 23, 6553−6557
© 2021 American Chemical Society
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a
Watson and co-workers found that the ligand effect could
control the stereoselectivity of palladium-catalyzed carbosily-
lation of internal symmetrical alkynes with trisubstituted silyl
iodides and primary alkyl zinc iodides. While the use of
(3,5-tBu2C6H3)3P (DrewPhos) led to syn selectivity,
(3,5-tBu2C6H3)2P(tBu) (JessePhos) gave rise to anti selectivity
(Scheme 1d).4c Similarly, syn-selective carbosilylation of
internal alkynes has been achieved via palladium-/copper-
cocatalyzed tandem silylboration/Suzuki reactions with a new
silane donor nucleophile (PhMe2SiBPin) and aryl bromide
electrophiles using the PCy3 ligand, wherein the PhMe2Si-[Cu]
intermediates are first formed and then directly added syn
across the CC bonds (Scheme 1e).5a In contrast, when a
similar Pd/Cu cooperative catalysis is used, the presence of
PPh3 enables the anti-selective silylallylation of electron-poor
internal alkynes with silyl boronic esters and allylcarbonates,
whereas omission of the ligand led to the syn-selective version
(Scheme 1f).5b Iron-catalyzed anti-selective silylalkylation of
terminal aliphatic alkynes with silyl boronic esters and alkyl
iodides occurred through direct addition of the in situ
generated R3Si-[Fe] intermediates across the CC bond
(Scheme 1g).5c Nevertheless, all existing approaches have been
limited to alkyne silyl-carbofucntionalization and only two
papers to date allowed the formation of functionalized anti-
alkenes from electron-deficient internal alkynes and terminal
aliphatic alkynes. A precise regioselective sequence control
between the silylation and carbofunctionalization processes to
realize carbosilylation of alkynes, especially including non-
symmetric terminal and internal alkynes, still remains
unprecedented.
We hypothesized that if more highly reactive carbon donors
were used as the electrophiles and the nucleophilicity of the in
situ generated PhMe2Si-[Cu] intermediates were tuned, the
palladium-catalyzed addition of the more highly reactive
carbon donors across the CC bond would take precedence
over the direct addition of the in situ generated PhMe2Si-[Cu]
intermediates, thus enabling exquisite control over both
regioselectivity and stereoselectivity to create new methods.
Herein, we report a new, general dual palladium-/copper-
catalyzed intermolecular trans-allenyl silylation of terminal
alkynes with propargyl acetates and PhMe2SiBpin to produce
(E)-silyl enallenes (Scheme 1h). The method allows propargyl
acetates as highly reactive allene precursors6 to enable
allenylation with alkynes prior to silylation and provides a
conceptually novel alkyne carbosilylation route to forge new,
valuable, functionalized vinyl silane scaffolds7 with excellent
regio-/stereoselectivity and functional group tolerance.
Table 1. Screening of Optimal Reaction Conditions
entry
variation from the standard conditions
none
yield (%)
1
72
0
trace
60
59
2
3
4
5
6
7
8
9
without Pd(PPh3)2Cl2, CuF2, or Na2CO3
PdCl2 instead of Pd(PPh3)2Cl2
PdCl2/PPh3 instead of Pd(PPh3)2Cl2
Pd(dppp)Cl2 instead of Pd(PPh3)2Cl2
Pd(dppf)Cl2 instead of Pd(PPh3)2Cl2
Pd(PPh3)4 instead of Pd(PPh3)2Cl2
Cu(OAc)2 instead of CuF2
CuCl instead of CuF2
10
trace
<5
40
25
41
10
11
CuI instead of CuF2
CuCl2 instead of CuF2
CuCl2 instead of CuF2
none
b
12
c
69
67
13
a
Standard reaction conditions unless specified otherwise: 1a (0.4
mmol), 2a (0.2 mmol), Me2(Ph)SiBPin (0.4 mmol), Pd(PPh3)2Cl2
(10 mol %), CuF2 (20 mol %), Na2CO3 (0.6 mmol), DMF (2 mL),
argon, 90 °C, 12 h. Only the E isomer was obtained, which was
determined by a 1H NMR and/or GC-MS analysis of the crude
b
c
product. NaF (40 mol %). 2a (1 mmol), DMF (4 mL), 20 h.
CuCl2, exhibited reactivity, but they were less efficient than
CuF2 (entries 8−11). Interestingly, using CuCl2 combined
with NaF gave results identical with those of CuF2 (entry 12),
suggesting that fluoride ions may promote Si−B bond
cleavage.7,8 Screening the effect of the CuF2 amount, bases
(such as Na2CO3, NaHCO3, K2CO3, and NEt3) and
temperatures (entries 1 and 13−18 in Table S1 in the
Supporting Information) proved that the reaction with 20 mol
% of CuF2 and Na2CO3 at 90 °C was the best option (entry 1).
Intriguingly, the conditions were applicable to a 1 mmol scale
of 2a, giving 3aa in 67% yield (entry 13).
With the optimized conditions in hand, we next explored the
reliable leaving groups in propargyl acetates 2 for the alkyne
allenylsilylation protocol (Scheme 2). A wide range of acyl
Scheme 2. Optimization of the Reliable Leaving Groups in
the Propargyl Acetates 2
Initial investigations on the allenylsilylation of 1-ethynyl-4-
fluorobenzene (1a) with 2-methyl-4-phenyl-but-3-yn-2-yl
acetate (2a) and Me2(Ph)SiBPin were performed (Table 1
and Table S1 in the Supporting Information). Allenylsilylation
of alkyne 1a with propargyl acetate 2a, Me2PhSiBPin (3a), 10
mol % of Pd(PPh3)2Cl2, 20 mol % of CuF2, and Na2CO3 in
DMF was executed smoothly, producing the desired product
(E)-3aa with a 72% yield (entry 1). It should be noted that
these parameters, including Pd(PPh3)2Cl2, CuF2, Na2CO3, and
phosphorus ligands (such as Ph3P, dppp, and dppf), are all
equally crucial for the success of the reaction, since omission of
each of them led to no isolation of 3aa (entries 2 and 3). While
using PdCl2 (entry 3) or Pd(PPh3)4 (entry 7) delivered a trace
amount of 3aa, other Pd catalysts, including PdCl2/PPh3,
Pd(dppp)Cl2, and Pd(dppf)Cl2, were highly reactive (entries
4−6). Other Cu catalysts, such as Cu(OAc)2, CuCl, CuI, and
groups, including Boc (2c), PhCO (2d), 4-MeC6H4CO (2e),
and 4-CF3C6H4CO (2f), were suitable to furnish 3aa, although
they had lower reactivity. However, using either bulky BuCO
(2b) or CF3SO2 (2g) led to no conversion of 2. Likewise, 2-
methyl-4-phenylbut-3-yn-2-ol (2h) was inert.
Encouraged by these results, we investigated the substrate
scope (Scheme 3). This alkyne allenylsilylation was applicable
to various substituents, such as F, Cl, Br, CF3, MeO, Ph, and
t
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a
halo positions (3ai−ak). While propargyl acetate 2l bearing an
electron-withdrawing p-CF3 group was efficiently converted to
3al with a 71% yield, propargyl acetate 2m with an electron-
donating p-MeO group delivered 3am in a diminished yield.
For propargyl acetates 2n,o with a p-Ph or an m-Me group the
reaction efficiently proceeded to give 3an,ao. In particular, the
thiophen-2-yl-substituted propargyl acetate 2p was well
accommodated (3ap). However, the alkyl-substituted prop-
argyl acetate 2q was inert. Using 3-methyl-1-phenyl-pent-1-yn-
3-yl acetate (2r) and 2,4-diphenylbut-3-yn-2-yl acetate (2s),
both smoothly underwent allenylsilylation to produce 3br,s in
moderate yields.
Scheme 3. Scope of the Alkynes 1 and Propargyl Acetates 2
The allenylsilylation protocol was compatible with a wide
array of terminal aryl alkynes (3ba−ma), but attempts to
allenylsilylate terminal alkyl alkyne, electron-poor alkynes and
internal alkynes failed (3na−pa). Phenylacetylene (1b) was
successfully treated with propargyl acetate 2a, Me2(Ph)SiBPin,
Pd(PPh3)2Cl2, and CuF2, giving 3ba in 68% yield. A range of
aryl substituents at the alkyne terminus, including 4-ClC6H4, 4-
BrC6H4, 4-CF3C6H4, 4-MeC6H4, 4-MeOC6H4, 4-BnOC6H4, 4-
PhC6H4, 3-ClC6H4, and 2-ClC6H4, were perfectly tolerated
and produced 3ca−3ka in good yields. Moreover, neither the
electronic nature nor the positions of these substituents
interfered with our target reaction. Aryl alkynes 1c,j,k, bearing
a Cl group at para, meta, or ortho positions on the aryl ring,
respectively, were all viable substrates (3ca,ja,ka). The reaction
could be applied to both strongly electron-withdrawing CF3-
substituted aryl alkynes and strongly electron-donating
alkyloxy (such as MeO and BnO)-substituted aryl alkynes
(3ea,ga,ha). Most importantly, halogen atoms (such as Cl and
Br) remain intact for further elaborations (3ca,da,ja,ka).
Notably, naphthalen-1-yl and thiophen-2-yl alkynes 1l,m
were transformed to 3la,ma, respectively, in good yields. The
resulting multisubstituted alkenes are fundamental motifs in
natural products, pharmaceuticals, and functional materials,
inspiring us to use such alkenes as the embedded functionality
of the known bioactive molecules to make them synthetically
useful. As expected, this allenylsilylation successfully forged
medicinally relevant motif-based alkenes,8 including febuxostat
derivative 3qa, empagliflozin derivative 3ra, estradiol valerate
derivative 3sa, and estrone derivative 3tm.
Consequently, a possible mechanism was proposed (Scheme
4).2−9 Oxidative addition of propargyl acetate 2a with the
Scheme 4. Possible Reaction Mechanisms
a
Reaction conditions: 1 (0.4 mmol), 2 (0.2 mmol), Me2(Ph)SiBPin
(0.4 mmol), Pd(PPh3)2Cl2 (10 mol %), CuF2 (20 mol %), Na2CO3
(0.6 mmol), DMF (2 mL), argon, 90 °C, 12 h.
active Pd(0) species affords the allenyl-PdOAc intermediate A
due to its activation by the gem-aryl electronic effect.6 This is
the reason that alkyl-substituted propargyl acetates have no
reactivity during the reaction. Subsequently, the intermediate
B, which is formed by the coordination of intermediate A with
alkyne 1a, undergoes a trans addition across the CC bond to
Me, on the aryl ring at the terminal alkyne in propargyl
acetates 2i−o (products 3ai−ao), and the electronic/steric
hindrance effect had an influence on the reaction. Notably,
halogen atoms, including F, Cl, and Br, were well tolerated,
hence providing the potential for further derivatization of the
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deliver the vinyl-Pd intermediate C. Transmetalation between
the intermediate C and the Cu−Si intermediate D, which is
generated via the reaction of Me2(Ph)SiBPin and the active
CuII species,5,8 leads to the formation of the vinyl-Pd-Si
intermediate E. Reductive elimination of the intermediate E
affords the desired product (E)-3 and regenerates the active
Pd(0) species. Anions, especially the fluoride anion with a
strong negative charge property, might react with the B unit
and thus promote the Si−B bond cleavage.
In summary, we have developed the first regio- and
stereoselective intermolecular anti-allenylsilylation of terminal
alkynes with propargyl acetates and Me2PhSiBPin using dual
palladium/copper cooperative catalysis for the synthesis of
(E)-silyl enallenes. The efficient allenyl-Pd intermediates
generated from highly reactive allene precursors, such as
propargyl acetates, are crucial to the success of this method,
wherein the cooperative Pd(PPh3)2Cl2 and CuF2 catalytic
system enables the selective formation of allenyl-Pd
intermediates and Si-Cu intermediates, allowing exquisitely
regioselective access to highly valuable (E)-1-silyl-2-allenyl
alkenes.
ACKNOWLEDGMENTS
■
We thank the National Natural Science Foundation of China
(Nos. 21625203 and 21871126), the Open Research Fund of
School of Chemistry and Chemical Engineering, Henan
Normal University (No. 2021ZD01), and the Jiangxi Province
Science and Technology Project (No. 20182BCB22007) for
financial support.
REFERENCES
■
(1) For recent reviews, see: (a) Flynn, A. B.; Ogilvie, W. W.
Stereocontrolled Synthesis of Tetrasubstituted Olefins. Chem. Rev.
2007, 107, 4698−4745. (b) Besset, T.; Poisson, T.; Pannecoucke, X.
Direct Vicinal Difunctionalization of Alkynes: An Efficient Approach
Towards the Synthesis of Highly Functionalized Fluorinated Alkenes.
Eur. J. Org. Chem. 2015, 2015, 2765−2789. (c) Xu, J.; Song, Q.
Radical Promoted Difunctionalization of Unsaturated Carbon-Carbon
Bonds in the Presence of Dioxygen. Youji Huaxue 2016, 36, 1151−
1162. (d) Xu, C.-H.; Li, Y.; Li, J.-H.; Xiang, J.-N.; Deng, W. Recent
advances in Radical-Mediated [2 + 2+m] Annulation of 1,n-Enynes.
Sci. China: Chem. 2019, 62, 1463−1475. (e) Mei, H.; Yin, Z.; Liu, J.;
Sun, H.; Han, J. Recent Advances on the Electrochemical
Difunctionalization of Alkenes/Alkynes. Chin. J. Chem. 2019, 37,
292−301. (f) Ren, X.; Lu, Z. Negishi Coupling for Highly Selective
Syntheses of Allenes via Ligand Effect and Mechanistic Study via
SAESI-MS/MS. Chin. J. Chem. 2019, 37, 1003−1008. (g) Liu, W.;
Kong, W. Ni-Catalyzed Stereoselective Difunctionalization of Alkynes.
Org. Chem. Front. 2020, 7, 3941−3955. (h) Duan, X.-F. Iron
Catalyzed Stereoselective Alkene Synthesis: a Sustainable Pathway.
Chem. Commun. 2020, 56, 14937−14961. (i) Li, M.; Wu, W.; Jiang,
H. Recent Advances in Silver-Catalyzed Transformations of Electroni-
cally Unbiased Alkenes and Alkynes. ChemCatChem 2020, 12, 5034−
5050. (j) Yao, H.; Hu, W.; Zhang, W. Difunctionalization of Alkenes
and Alkynes via Intermolecular Radical and Nucleophilic Additions.
Molecules 2021, 26, 105.
ASSOCIATED CONTENT
■
sı
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.orglett.1c02364.
Experimental procedures, characterization of all com-
pounds, NMR spectra (PDF)
(2) For reviews on the carbosilylation of alkynes, see: (a) Lim, D. S.
W.; Anderson, E. A. Synthesis of Vinylsilanes. Synthesis 2012, 44,
983−1010. (b) Aronica, L. A.; Caporusso, A. M.; Salvadori, P.
Synthesis and Reactivity of Silylformylation Products Derived from
Alkynes. Eur. J. Org. Chem. 2008, 2008, 3039−3060. (c) Albano, G.;
Aronica, L. A. From Alkynes to Heterocycles through Metal-
Promoted Silylformylation and Silylcarbocyclization Reactions.
Catalysts 2020, 10, 1012.
AUTHOR INFORMATION
■
Corresponding Authors
Qiu-An Wang − State Key Laboratory of Chemo/Biosensing
and Chemometrics, Hunan University, Changsha 410082,
People’s Republic of China; Email: wangqa@hnu.edu.cn
Jin-Heng Li − State Key Laboratory of Chemo/Biosensing and
Chemometrics, Hunan University, Changsha 410082,
People’s Republic of China; Key Laboratory of Jiangxi
Province for Persistent Pollutants Control and Resources
Recycle, Nanchang Hangkong University, Nanchang 330063,
People’s Republic of China; State Key Laboratory of Applied
Organic Chemistry, Lanzhou University, Lanzhou 730000,
People’s Republic of China; School of Chemistry and
Chemical Engineering, Henan Normal University, Xinxiang,
Henan 475004, People’s Republic of China; orcid.org/
0000-0001-7215-7152; Email: jhli@hnu.edu.cn
(3) For representative papers, see: (a) Matsuda, I.; Ogiso, A.; Sato,
S.; Izumi, Y. An Efficient Silylformylation of Alkynes Catalyzed by
Tetrarhodium Dodecacarbonyl. J. Am. Chem. Soc. 1989, 111, 2332−
2333. (b) Ojima, I.; Ingallina, P.; Donovan, R. J.; Clos, N.
Silylformylation of 1-Hexyne Catalyzed by Rhodium-Cobalt Mixed-
Metal Carbonyl Clusters. Organometallics 1991, 10, 38−41. (c) Doyle,
M. P.; Shanklin, M. S. Highly Efficient Regioselective Silylcarbony-
lation of Alkynes Catalyzed by Dirhodium(II) Perfluorobutyrate.
Organometallics 1993, 12, 11−12. (d) Matsuda, I.; Fukuta, Y.;
Tsuchihashi, T.; Nagashima, H.; Itoh, K. Rhodium-Catalyzed
Silylformylation of Acetylenic Bonds: Its Scope and Mechanistic
Considerations. Organometallics 1997, 16, 4327−4345. (e) Matsuda,
I.; Takeuchi, K.; Itoh, K. Rhodium-Catalyzed Intermolecular
Silylcarbamoylation of Acetylenic Bonds. Tetrahedron Lett. 1999, 40,
2553−2556. (f) Alonso, M. A.; Casares, J. A.; Espinet, P.; Vallés, E.;
Soulantica, K. Efficient Silylformylation of Alkynes Catalyzed by
Rhodium Complexes with P,N Donor Ligands. Tetrahedron Lett.
2001, 42, 5697−5700. (g) Biffis, A.; Conte, L.; Tubaro, C.; Basato,
M.; Aronica, L. A.; Cuzzola, A.; Caporusso, A. M. Highly Selective
Silylformylation of Internal and Functionalised Alkynes with a
Cationic Dirhodium(II) Complex Catalyst. J. Organomet. Chem.
2010, 695, 792−798. (h) Chen, B.; Wu, X.-F. Rhodium-Catalyzed
Carbonylative Synthesis of Benzosilinones. Org. Lett. 2019, 21, 2899−
2902. (i) Chen, B.; Wu, X.-F. Palladium-Catalyzed Carbonylative
Synthesis of Benzosilinones from (2-Iodophenyl)Hydrosilanes and
Terminal Alkynes. Adv. Synth. Catal. 2019, 361, 3441−3445.
Author
Liang-Feng Yang − State Key Laboratory of Chemo/
Biosensing and Chemometrics, Hunan University, Changsha
410082, People’s Republic of China; Key Laboratory of
Jiangxi Province for Persistent Pollutants Control and
Resources Recycle, Nanchang Hangkong University,
Nanchang 330063, People’s Republic of China
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.orglett.1c02364
Notes
The authors declare no competing financial interest.
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(j) Fukumoto, Y.; Hagihara, M.; Kinashi, F.; Chatani, N. Switch in
Stereoselectivity Caused by the Isocyanide Structure in the Rhodium-
Catalyzed Silylimination of Alkynes. J. Am. Chem. Soc. 2011, 133,
10014−10017. (k) Fukumoto, Y.; Shimizu, H.; Tashiro, A.; Chatani,
N. Synthesis of α-Silylmethyl-α,β-Unsaturated Imines by the
Rhodium-Catalyzed Silylimination of Primary-Alkyl-Substituted Ter-
minal Alkynes. J. Org. Chem. 2014, 79, 8221−8227.
(4) (a) Chatani, N.; Amishiro, N.; Murai, S. A New Catalytic
Reaction Involving Oxidative Addition of Iodotrimethylsilane
(Me3SiI) to Palladium(0). Synthesis of Stereodefined Enynes by the
Coupling of Me3SiI, Acetylenes, and Acetylenic Tin Reagents. J. Am.
Chem. Soc. 1991, 113, 7778−7780. (b) Chatani, N.; Amishiro, N.;
Morii, T.; Yamashita, T.; Murai, S. Pd-Catalyzed Coupling Reaction
of Acetylenes, Iodotrimethylsilane, and Organozinc Reagents for the
Stereoselective Synthesis of Vinylsilanes. J. Org. Chem. 1995, 60,
1834−1840. (c) Wisthoff, M. F.; Pawley, S. B.; Cinderella, A. P.;
Watson, D. A. Stereoselective Synthesis of Cis- and Trans-
Tetrasubstituted Vinyl Silanes Using a Silyl-Heck Strategy and
Hiyama Conditions for Their Cross-Coupling. J. Am. Chem. Soc.
2020, 142, 12051−12055.
to Enantioenriched Organosilanes from Enals and β-Silyl Enones:
Carbene Organocatalysis. Angew. Chem., Int. Ed. 2018, 57, 4594−
4598.
(8) Feng, J.-J.; Mao, W.; Zhang, L.; Oestreich, M. Activation of the
Si-B Interelement Bond Related to Catalysis. Chem. Soc. Rev. 2021,
50, 2010−2073.
(9) (a) Bellos, I.; Kontzoglou, K.; Psyrri, A.; Pergialiotis, V.
Febuxostat Administration for the Prevention of Tumour lysis
Syndrome: A Meta-Analysis. J. Clin. Pharm. Ther. 2019, 44, 525−
533. (b) Hu, S.; Sun, W.; Wang, Y.; Yan, H. Design, Synthesis and
Anticancer Activities of Halogenated Phenstatin Analogs as Micro-
tubule Destabilizing Agent. Med. Chem. Res. 2019, 28, 465−472.
(c) Li, Y.; Zhao, C. Progress in Clinical Application of Estradiol
Valerate Tablets in Gynecology and Obstetrics. China Pharm. 2014,
25, 933. (d) Chen, A. Y.; Lee, A. J.; Jiang, X.-R.; Zhu, B. T. Chemical
Synthesis of Six Novel 17β-Estradiol and Estrone Dimers and Study of
Their Formation Catalyzed by Human Cytochrome P450 Isoforms. J.
Med. Chem. 2007, 50, 5372−5381.
(5) (a) Shintani, R.; Kurata, H.; Nozaki, K. Intermolecular Three-
Component Arylsilylation of Alkynes under Palladium/Copper
Cooperative Catalysis. J. Org. Chem. 2016, 81, 3065−3069.
(b) Vercruysse, S.; Cornelissen, L.; Nahra, F.; Collard, L.; Riant, O.
CuI/Pd0 Cooperative Dual Catalysis: Tunable Stereoselective
Construction of Tetra-Substituted Alkenes. Chem. - Eur. J. 2014, 20,
1834−1838. (c) Iwamoto, T.; Nishikori, T.; Nakagawa, N.; Takaya,
H.; Nakamura, M. Iron-Catalyzed anti-Selective Carbosilylation of
Internal Alkynes. Angew. Chem., Int. Ed. 2017, 56, 13298−13301.
(d) Fujihara, T.; Tani, Y.; Semba, K.; Terao, J.; Tsuji, Y. Copper-
Catalyzed Silacarboxylation of Internal Alkynes by Employing Carbon
Dioxide and Silylboranes. Angew. Chem., Int. Ed. 2012, 51, 11487−
11490.
(6) For selected reviews and papers, see: (a) Guo, L. N.; Duan, X.
H.; Liang, Y. M. Palladium-Catalyzed Cyclization of Propargylic
Compounds. Acc. Chem. Res. 2011, 44, 111−122. (b) Yu, S.; Ma, S.
Allenes in Catalytic Asymmetric Synthesis and Natural Product
Syntheses. Angew. Chem., Int. Ed. 2012, 51, 3074−3112. (c) Alcaide,
B.; Almendros, P. Progress in Allene Chemistry. Chem. Soc. Rev. 2014,
43, 2886−2887. (d) Ye, J.; Ma, S. Palladium-Catalyzed Cyclization
Reactions of Allenes in the Presence of Unsaturated Carbon-Carbon
Bonds. Acc. Chem. Res. 2014, 47, 989−1000. (e) Song, X.-R.; Yang,
R.; Xiao, Q. Recent Advances in the Synthesis of Heterocyclics via
Cascade Cyclization of Propargylic Alcohols. Adv. Synth. Catal. 2021,
363, 852−876. (f) Jiao, Z.; Shi, Q.; Zhou, J. S. Asymmetric
Intermolecular Heck Reaction of Propargylic Acetates and Cyclo-
alkenes to Access Fused Cyclobutenes. Angew. Chem., Int. Ed. 2017,
56, 14567−14571. (g) Teng, S.; Jiao, Z.; Chi, Y. R.; Zhou, J. S.
Asymmetric Wacker-Type Oxyallenylation and Azaallenylation of
Cyclic Alkenes. Angew. Chem., Int. Ed. 2020, 59, 2246−2250.
(h) Teng, S.; Chi, Y. R.; Zhou, J. S. Enantioselective Three-
Component Coupling of Heteroarenes, Cycloalkenes and Propargylic
Acetates. Angew. Chem., Int. Ed. 2021, 60, 4491−4495.
(7) For selected reviews and papers, see: (a) Hosomi, A.
Characteristics in the Reactions of Allylsilanes and Their Applications
to Versatile Synthetic Equivalents. Acc. Chem. Res. 1988, 21, 200−206.
(b) Langkopf, E.; Schinzer, D. Uses of Silicon-Containing
Compounds in the Synthesis of Natural Products. Chem. Rev. 1995,
95, 1375−1408. (c) Colvin, E. W. In The Chemistry of Organic Silicon
Compounds; Rappoport, Z., Apeloig, Y., Eds.; Wiley: 2003; p 1667. .
(d) Hiyama, T.; Oestreich, M. Organosilicon Chemistry−Novel
Approaches and Reactions; Wiley-VCH: 2019. (e) Balskus, E. P.;
Jacobsen, E. N. α,β-Unsaturated β-Silyl Imide Substrates for Catalytic,
Enantioselective Conjugate Additions: A Total Synthesis of
(+)-Lactacystin and the Discovery of a New ProteasomeIinhibitor.
J. Am. Chem. Soc. 2006, 128, 6810−6812. (f) Gilles, P.; Py, S. SmI2-
Mediated Cross-Coupling of Nitrones with β-Silyl Acrylates:
Synthesis of (+)-Australine. Org. Lett. 2012, 14, 1042−1045.
(g) Zhang, Y.; Huang, J.; Guo, Y.; Li, L.; Fu, Z.; Huang, W. Access
6557
https://doi.org/10.1021/acs.orglett.1c02364
Org. Lett. 2021, 23, 6553−6557