- Advances in siloxane-based coupling reactions: Application of palladium-mediated allyl-aryl coupling to the synthesis of pancratistatin derivatives. The formal total synthesis of (±)-7-deoxypancratistatin
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Palladium-mediated coupling of an allylic carbonate and an aryl siloxane has been applied to the formal total synthesis of 7-deoxypancratistatin and pancratistatin analogues. The key coupling reaction involved the use of a novel palladium olefin complex resulting in regio- and stereoselective arylation yielding a tetracyclic A-C ring intermediate. The observed regioselectivity of the coupling reaction was consistent with a model in which an unsymmetrical p-allyl palladium complex was formed. Coupling of a variety of substituted phenyl siloxane derivatives was achieved using the new Pd(0) system to provide access to novel pancratistatin derivatives.
- Shukla, Krupa H.,DeShong, Philip
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- An ultrahigh-loading single-site Zn catalyst for efficient and ambient hydrogen generation from silanes
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A nitrogen-doped carbon-supported ultrahigh-loading single-site Zn catalyst (Zn1-N-C, 28.3 wt%) was facilely constructed by using a ball milling strategy. With atomically dispersed ZnN3O sites, the catalyst showed superior catalytic properties for the generation of H2 from silane/alcohol pairs, and scale-up and recycling tests demonstrated its great potential in practical applications.
- Chen, Hongyu,He, Qian,He, Xiaohui,Ji, Hongbing,Wang, Pengbo
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supporting information
p. 3828 - 3832
(2022/03/31)
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- Rhodium(III)-Catalyzed Direct C-H Arylation of Various Acyclic Enamides with Arylsilanes
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The stereoselective β-C(sp2)-H arylation of various acyclic enamides with arylsilanes via Rh(III)-catalyzed cross-coupling reaction was illustrated. The methodology was characterized by extraordinary efficacy and stereoselectivity, a wide scope of substrates, good functional group tolerance, and the adoption of environmentally friendly arylsilanes. The utility of this present method was evidenced by the gram-scale synthesis and further elaboration of the product. In addition, Rh(III)-catalyzed C-H activation is considered to be the critical step in the reaction mechanism.
- Li, Xiaolan,Sun, Kai,Shen, Wenjuan,Zhang, Yong,Lu, Ming-Zhu,Luo, Xuzhong,Luo, Haiqing
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supporting information
p. 31 - 36
(2021/01/09)
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- Cobalt-Catalyzed Defluorosilylation of Aryl Fluorides via Grignard Reagent Formation
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Transition-metal-catalyzed transformations of the carbon-fluorine bond not only tackle an interesting problem of challenging bond activation but also offer new synthetic strategies where the relatively inert C-F bond is converted to versatile functional groups. Herein we report a practical cobalt-catalyzed silylation of aryl fluorides that uses a cheap electrophilic silicon source with magnesium. This method is compatible with various silicon sources and can be operated under aerobic conditions. Mechanistic studies support the in situ formation of a Grignard reagent, which is captured by the electrophilic silicon source.
- Cho, Hyungdo,Cho, Seung Hwan,Jang, Minjae,Jeong, Jongheon,Kim, Hyunseok,Lee, Eunsung,Lim, Soobin
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supporting information
p. 7387 - 7392
(2020/10/12)
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- High Production of Hydrogen on Demand from Silanes Catalyzed by Iridium Complexes as a Versatile Hydrogen Storage System
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The catalytic dehydrogenative coupling of silanes and alcohols represents a convenient process to produce hydrogen on demand. The catalyst, an iridium complex of the formula [IrCp?(Cl)2(NHC)] containing an N-heterocyclic carbene (NHC) ligand functionalized with a pyrene tag, catalyzes efficiently the reaction at room temperature producing H2 quantitatively within a few minutes. As a result, the dehydrogenative coupling of 1,4-disilabutane and methanol enables an effective hydrogen storage capacity of 4.3 wt % that is as high as the hydrogen contained in the dehydrogenation of formic acid, positioning the silane/alcohol pair as a potential liquid organic hydrogen carrier for energy storage. In addition, the heterogenization of the iridium complex on graphene presents a recyclable catalyst that retains its activity for at least 10 additional runs. The homogeneous distribution of catalytic active sites on the basal plane of graphene prevents diffusion problems, and the reaction kinetics are maintained after immobilization.
- Ventura-Espinosa, David,Sabater, Sara,Carretero-Cerdán, Alba,Baya, Miguel,Mata, Jose A.
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p. 2558 - 2566
(2018/03/13)
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- Ligand-promoted oxidative cross-coupling of aryl boronic acids and aryl silanes by palladium catalysis
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The first cross-coupling reaction between aryl silanes and aryl boronic acids is described. This transformation represents one of the very few examples of coupling reactions between two nucleophilic organometallic reagents and provides a new method for the formation of biaryl compounds. The successful development of this reaction was enabled by the use of commercially available 2,2-bis(diphenylphosphino)-1,1-binaphthyl (BINAP) as the ligand. A small amount of BINAP (3 mol %) was sufficient to suppress the formation of the homocoupling products, and the reaction yielded the cross-coupling products with high selectivity under mild conditions, even when the ratio of the two coupling partners was 1:1.
- Yu, Jingxun,Liu, Jun,Shi, Guangfa,Shao, Changdong,Zhang, Yanghui
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supporting information
p. 4079 - 4082
(2015/03/30)
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- One-pot synthesis and structural characterization of poly(alkoxysilane)s catalyzed by silver-gold complexes
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Combinative one-pot Si-Si/Si-O dehydrocoupling of hydrosilanes with alcohols (1:1.5 mole ratio), mediated by a mixture of AgNO3-AuCl 3 (100/1 mole ratio) rapidly produced poly(alkoxysilane)s in reasonably high yield. The addition of small amount of gold complex to the reaction mixture effectively accelerated the coupling reaction compared to the reaction rate with AgNO3 alone. The hydrosilanes include p-X-C 6H4SiH3 (X = H, CH3, OCH 3, F), PhCH2SiH3, and (PhSiH2) 2. The alcohols include MeOH, EtOH, iPrOH, PhOH, and CF 3(CF2)2CH2OH. The weight average molecular weight and polydispersity of the poly(alkoxysilane)s were in the range of 1,600~8,000 Dalton and 1.4~3.5, respectively. The dehydrocoupling reactions of phenylsilane with ethanol (1:3 mole ratio) in the presence of the Ag-Au complexes gave only triethoxyphenylsilane. Copyright
- Cheong, Hyeonsook,Roh, Sung-Hee,Cho, Myong-Shik,Kim, Myoung-Hee,Woo, Hee-Gweon,Yang, Kap-Seung,Kim, Bo-Hye,Jun, Jin,Sohn, Honglae
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p. 702 - 705
(2013/06/26)
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- Meerwein's reagent mediated, significantly enhanced nucleophilic fluorination on alkoxysilanes
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We developed a new facile method to fluorosilanes from alkoxysilanes using Meerwein's reagent. Our protocol afforded fluorosilanes in excellent yields in various organic solvents including acetonitrile under mild reaction conditions at room temperature. We also proposed a reaction mechanism with the probable silyloxonium intermediates. Georg Thieme Verlag Stuttgart · New York.
- Jorapur, Yogesh R.,Shimada, Toyoshi
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supporting information; experimental part
p. 1064 - 1068
(2012/06/17)
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- Rhodium(I)-catalyzed synthesis of aryltriethoxysilanes from arenediazonium tosylate salts with triethoxysilane
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An efficient method for the preparation of aryltriethoxy-silanes from arenediazonium tosylate salts has been developed, which expands the substrates of rhodium-catalyzed silylation from iodides, bromides, and triflates to diazonium salts. A new method for hydrodediazoniation has also been explored.
- Tang, Zhi Yong,Zhang, Yuan,Wang, Tao,Wang, Wei
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supporting information; experimental part
p. 804 - 808
(2010/06/14)
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- Palladium nanoparticle catalyzed hiyama coupling reaction of benzyl halides
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An efficient Hiyama coupling reaction between benzylic halide and aryltrialkoxysilane using Pd nanoparticles has been developed. This procedure accommodates various functional groups to yield a diverse range of diarylmethanes which are ubiquitous units of natural products and pharmaceuticals.
- Srimani, Dipankar,Bej, Ansuman,Sarkar, Amitabha
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supporting information; experimental part
p. 4296 - 4299
(2010/09/04)
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- Convenient synthesis of palladium nanoparticles and catalysis of hiyama coupling reaction in water
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An efficient synthesis of Pd nanoparticles in water has been developed using a Fischer carbene complex of tungsten as the reductant and PEG as the capping agent. The colloidal palladium (1 mol %) efficiently catalyzes Hiyama cross-coupling reactions performed in air. Excellent yields of products were obtained with a wide range of substrates. Catalytic activity and stability of the nanoparticles were found to be inversely correlated.
- Srimani, Dipankar,Sawoo, Sudeshna,Sarkar, Amitabha
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p. 3639 - 3642
(2008/02/13)
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- Improved synthesis of aryltrialkoxysilanes via treatment of aryl Grignard or lithium reagents with tetraalkyl orthosilicates
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General reaction conditions for the synthesis of aryl(trialkoxy)silanes from aryl Grignard and lithium reagents and tetraalkyl orthosilicates (Si(OR)4) have been developed. Ortho-, meta-, and para-substituted bromoarenes underwent efficient metalation and silylation at low temperature to provide aryl siloxanes. Mixed results were obtained with heteroaromatic substrates: 3-bromothiophene, 3-bromo-4-methoxypyridine, 5-bromoindole, and N-methyl-5-bromoindole underwent silylation in good yield, whereas a low yield of siloxane was obtained from 2-bromofuran, and 2-bromopyridine failed to give silylated product. The synthesis of siloxanes via organolithium and magnesium reagents was limited by the formation of di- and triarylated silanes (Ar 2Si(OR)2 and Ar3SiOR, respectively) and dehalogenated (Ar-H) byproducts. Silylation at low temperature gave predominantly monoaryl siloxanes, without requiring a large excess of the electrophile. Optimal reaction conditions for the synthesis of siloxanes from aryl Grignard reagents entailed addition of arylmagnesium reagents to 3 equiv of tetraethyl- or tetramethyl orthosilicate at -30 °C in THF. Aryllithium species were silylated using 1.5 equiv of tetraethyl- or tetramethyl orthosilicate at -78 °C in ether.
- Manoso, Amy S.,Ahn, Chuljin,Soheili, Arash,Handy, Christopher J.,Correia, Reuben,Seganish, W. Michael,DeShong, Philip
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p. 8305 - 8314
(2007/10/03)
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- One-pot synthesis of poly(alkoxysilane)s by Si-Si/Si-O dehydrocoupling of silanes with alcohols using Group IV and VIII metallocene complexes
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Si-Si/Si-O dehydrocoupling reactions of silanes with alcohols (1:1.5 mole ratio), catalyzed by Cp2MCl2/Red-Al (M=Ti, Zr) and Cp2M′ (M′=Co, Ni), produced poly(alkoxysilane)s in one-pot in high yield. The silanes included p-X-C6H4SiH3 (X=H, CH3, OCH3, F), PhCH2SiH3, and (PhSiH2)2. The alcohols were MeOH, EtOH, iPrOH, PhOH, and CF3(CF2) 2CH2OH. The weight average molecular weight of the poly(alkoxysilane)s ranged from 600 to 8000. The dehydrocoupling reactions of phenylsilane with ethanol (1:1.5 mole ratio) using Cp2HfCl2/Red-Al and phenylsilane with ethanol (1:3 mole ratio) using Cp2TiCl2/Red-Al gave only triethoxyphenylsilane as product.
- Kim, Bo-Hye,Cho, Myong-Shik,Kim, Mi-Ae,Woo, Gee-Gweon
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- Improved synthesis of aryltriethoxysilanes via palladium(O)-catalyzed silylation of aryl iodides and bromides with triethoxysilane
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The scope of the palladium-catalyzed silylation of aryl halides with triethoxysilane has been expanded to include aryl bromides. A more general Pd(0) catalyst/ligand system has been developed that activates bromides and iodides: palladium(O) dibenzylideneacetone (Pd(dba)2) is activated with 2-(di-tert-butylphosphino)biphenyl (Buchwald's ligand) (1:2 mol ratio of Pd/phosphine). Electronrich para- and meta-substituted aryl halides (including unprotected aniline and phenol derivatives) undergo silylation to form the corresponding aryltriethoxysilane in fair to excellent yield; however, ortho-substituted aryl halides failed to be silylated.
- Manoso,DeShong
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p. 7449 - 7455
(2007/10/03)
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- Palladium-catalyzed cross-coupling reaction of aryltriethoxysilanes with aryl bromides under basic aqueous conditions
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Aryltriethoxysilanes were cross-coupled with aryl bromides in high yield in the presence of a palladium catalyst and aqueous sodium hydroxide.
- Murata,Shimazaki,Watanabe,Masuda
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p. 2231 - 2233
(2007/10/03)
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