- The product of catalysed diboration of bis(4-methoxyphenyl)ethyne by bis-(pinacolato-O,O′)diboron
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The title compound, (Z)-1,2-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,2-bis(4- methoxyphenyl)-ethene, C28H38B2O6, has a cis arrangement of two boronate ester substituents and two 4-methoxyphenyl substituents on its central C=C double bond, which shows a slight twist of ca 8.5°. All four substituents are rotated considerably out of the alkene plane to reduce steric hindrance. The BO2C2 five-membered rings have a twist conformation.
- Clegg, William,Scott, Andrew J.,Lesley, Gerry,Marder, Todd B.,Norman, Nicholas C.
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Read Online
- Sodium-metal-promoted reductive 1,2-syn-diboration of alkynes with reduction-resistant trimethoxyborane
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Reductive 1,2-diboration of alkynes has been accomplished by means of sodium dispersion in the presence of trimethoxyborane as a reduction-resistant boron electrophile. Two boron moieties can be introduced onto alkynes with excellent syn selectivity to afford the corresponding (Z)-1,2-diborylalkenes. Bis(borate) species generated in situ can be involved in one-pot Suzuki-Miyaura arylation, formal arylboration of alkynes thus being executed.
- Fukazawa, Mizuki,Ito, Shiori,Nogi, Keisuke,Takahashi, Fumiya,Yorimitsu, Hideki
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p. 1171 - 1179
(2020/10/18)
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- Divergent and Stereoselective Synthesis of Tetraarylethylenes from Vinylboronates
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The synthesis of a new tetraborylethylene (TBE) is reported, and its application in the preparation of [4+0]-tetraarylethenes (TAEs) is elucidated. TAEs have widespread applications in material science and supramolecular chemistry due to their aggregation-induced emission (AIE) properties. The divergent and stereoselective synthesis of [3+1]-, [2+2]-, and [2+1+1]-TAEs via multiple couplings of vinylboronates with aryl bromides is demonstrated. These couplings feature a broad substrate scope and excellent functional group compatibility due to mild reaction conditions. Facile access to various tetraarylethenes is provided. This strategy represents an important complement to the conventional methods employed for the synthesis of TAEs, and would be a valuable tool for synthesizing TAE-based molecules useful in functional materials, biological imaging and chemical sensing.
- Stang, Peter J.,Yao, Yisen,Zhang, Minghao,Zhao, Wanxiang
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supporting information
p. 20090 - 20098
(2020/09/02)
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- Synthesis of bis-BN-Naphthalene-Fused Oxepins and Their Photoluminescence including White-Light Emission
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A series of novel bis-BN-naphthalene-fused oxepin derivatives were synthesized via a Pd-catalyzed tandem reaction from brominated 2,1-borazaronaphthalenes and cis-bis(boryl)alkenes. X-ray crystallographic analysis revealed that bis-BN-naphthalene-fused oxepins feature a planar framework. The electronic and photophysical properties of the novel BN-naphthalene-fused oxepins were investigated by UV-vis and fluorescence spectroscopies and density functional theory (DFT) calculations, which disclosed the distinct electronic and photophysical properties of the analogous hydrocarbon system. Interestingly, dual-fluorescent emissions were observed upon dissolving N-substituted derivatives 10-14 in dimethyl sulfoxide. Tunable emission colors especially for white-light emissions can be achieved by controlling the ratio of solvents, concentration, or temperature using only a single-molecule compound.
- Tian, Dawei,Li, Qian,Zhao, Yifan,Wang, Zijia,Li, Wenbin,Xia, Shuling,Xing, Siyang,Zhu, Bolin,Zhang, Jianying,Cui, Chunming
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supporting information
p. 526 - 536
(2020/02/04)
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- Copper-catalyzed borylation reactions of alkynes and arynes
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One, two, three, four: A copper(I)-phosphine complex catalyzes the diborylation of alkynes and arynes, and the tri- or tetraborylation of propargyl ethers (see scheme; pin=pinacolato). In the latter cases, the C-O bond(s) as well as the C≡C bond are borylated in one pot. Furthermore, a diborylation product serves as an intermediate in the efficient synthesis of ortho-terphenyls with pharmacological activity.
- Yoshida, Hiroto,Kawashima, Shota,Takemoto, Yuki,Okada, Kengo,Ohshita, Joji,Takaki, Ken
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supporting information; experimental part
p. 235 - 238
(2012/02/16)
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- Palladium-catalyzed double cross-coupling reaction of 1,2- bis(pinacolatoboryl)alkenes and -arenes with 2,2′-dibromobiaryls: Annulative approach to functionalized polycyclic aromatic hydrocarbons
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This study demonstrates that the double cross-coupling reaction of 1,2-bis(pinacolatoboryl)alkenes and -arenes with 2,2′-dibromobiaryls proceeds smoothly with the aid of a catalytic amount of Pd(PPh3) 4 in the presence of excess base to give a variety of polycyclic aromatic hydrocarbons, such as phenanthrenes, [5]helicene, dithienobenzenes, triphenylenes, dibenzo[g,p]chrysenes, and triphenyleno[1,2-b:4,3-b′] dithiophenes in good to high yields. It is noteworthy that the annulations using 2,2′-dibromooctafluorobiphenyl as an electrophile furnish the otherwise difficult to synthesize octafluorophenanthrenes and semi-fluorinated dibenzo[g,p]chrysenes in high yields.
- Shimizu, Masaki,Nagao, Ikuhiro,Tomioka, Yosuke,Kadowaki, Tsugumi,Hiyama, Tamejiro
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experimental part
p. 8014 - 8026
(2011/11/05)
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- Highly efficient monophosphine platinum catalysts for alkyne diboration
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Automated parallel screening using a series of in situ generated platinum(0) phosphine complexes has allowed the identification of improved catalysts for the diboration of alkynes using bis(pinacolato)diboron (B2(pin)2, pin = OCMe2CMe2O). A selection of phosphines were added to [Pt(NBE)3] (NBE = norbornene), which contains only labile mono-olefin ligands, and the activity of the resulting solutions as catalysts for the diboration of 4-CF3C6H4C≡CC6H 4CF3-4′ 1 by B2(pin)2 was investigated by in situ GC-MS and/or NMR spectroscopy. This allowed the optimum phosphine : platinum stoichiometry to be identified as 1 : 1, and the large differences in catalyst activity depending on the nature of the phosphine to be quantified. The best phosphines employed in the study, PCy3 and PPh2(o-Tol) (o-Tol = C6H4Me-o), give activities orders of magnitude greater than the worst, such as P(C6F5)3 and PBut3. The monophosphine catalysts function much more efficiently than previous catalysts for a range of alkynes allowing diborations to be performed at ambient temperatures. The diboration of strained cyclic alkenes and some vinyl- and allyl-arenes proceeded well, although the catalysts were inactive for other olefinic systems examined. As a result of these studies, the isolable and stable compound [Pt(PCy3)(η2-C2H4) 2] was identified as an excellent catalyst for alkyne diboration even at room temperature.
- Thomas,Souza,Marder
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p. 1650 - 1656
(2007/10/03)
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- Synthesis and characterization of platinum(II)-Bis(boryl) catalyst precursors for diboration of alkynes and diynes: Molecular structures of cis-[(PPh3)2Pt(B-4-Butcat)2], cis-[(PPh3)2Pt(Bcat)2], cis-[(dppe)Pt(Bcat)2], cis-[(dppb)Pt(Bcat)2]
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The reactions of the B-B-bonded compounds B2(cat)2 (cat = 1,2-O2C6H4) (1a), B2(4-But-cat)2 (1b), and B2(OCMe2CMe2O)2 (1c) with the Pt(0)-bis(phosphine) complex [(PPh3)2Pt(η-C2H4)] (4) via oxidative addition of the B-B bond yield cis-bis(boryl) Pt(II) complexes. The molecular structures of cis-[(PPh3)2Pt(Bcat)2]·C 6D6 (3a) and cis-[(PPh3)2Pt(B-4-Butcat)2] (3b) were determined by single-crystal X-ray diffraction. Reaction of 3a with 1 equiv of the bidentate phosphine dppe (Ph2PCH2CH2PPh2) or dppb (Ph2P(CH2)4PPh2) proceeds smoothly in toluene to give cis-[(dppe)Pt(Bcat)2] (5a) and cis-[(dppb)Pt(Bcat)2] (5b), respectively, which have also been characterized by X-ray diffraction. Compounds 3a,b and 4 are highly active catalyst precursors for the diboration of alkynes and 1,3-diynes. X-ray crystal structures of (E)-(4-MeOC6H4)C(Bcat)=CH(Bcat) (10c), (Z)-(C6H5)C(Bcat)=C(C6H5)(Bcat) (10e), and (Z,Z)-(4-MeOC6H4)C(Bcat)=C(Bcat)C(Bcat)=C(4-MeOC 6H4)(Bcat) (14a) confirm the cis stereochemistry of the boron substituents in three representative cases, namely, products of the catalyzed diboration of the terminal alkyne 4-MeOC6H4C=CH, the internal alkyne PhC=CPh, and the tetraboration of the diyne 4,4′-MeOC6H4C=CC=CC6H4OMe. The presence of the C=CSiMe3 moiety in catalytic reactions gives rise to additional products other than those derived from the diboration of the alkyne group. Metathetical reactions involving the diboron reagent and products derived from C-Si bond cleavage give rise to novel tris(boronate esters) as a result of the subsequent diboration of the C=CB(OR2) moieties formed by this competing process. The absence of catalytic activity using compound 5a, the extremely low activity of 5b, and the strong decrease in activity of 3b in the presence of added PPh3 suggests that phosphine dissociation is a critical step in the catalytic pathway.
- Lesley, Gerry,Nguyen, Paul,Taylor, Nicholas J.,Marder, Todd B.,Scott, Andrew J.,Clegg, William,Norman, Nicholas C.
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p. 5137 - 5154
(2008/10/08)
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