- Intramolecular Halo Stabilization of Silyl Cations—Silylated Halonium- and Bis-Halo-Substituted Siliconium Borates
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The stabilizing neighboring effect of halo substituents on silyl cations was tested for a series of peri-halo substituted acenaphthyl-based silyl cations 3. The chloro- (3 b), bromo- (3 c), and iodo- (3 d) stabilized cations were synthesized by the Corey protocol. Structural and NMR spectroscopic investigations for cations 3 b–d supported by the results of density functional calculations, which indicate their halonium ion nature. According to the fluorobenzonitrile (FBN) method, the silyl Lewis acidity decreases along the series of halonium ions 3, the fluoronium ion 3 a being a very strong and the iodonium ion 3 d a moderate Lewis acid. Halonium ions 3 b and 3 c react with starting silanes in a substituent redistribution reaction and form siliconium ions 4 b and 4 c. The structure of siliconium borate 4 c2[B12Br12] reveals the trigonal bipyramidal coordination environment of the silicon atom with the two bromo substituents in the apical positions.
- Merk, Anastasia,Bührmann, Lukas,Kordts, Natalie,G?rtemaker, Katharina,Schmidtmann, Marc,Müller, Thomas
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- Air-stable nickel precatalysts for fast and quantitative cross-coupling of aryl sulfamates with aryl neopentylglycolboronates at room temperature
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A library containing 10 air-stable NiIIX(Aryl)(PCy3)2 complexes as precatalysts (X = Cl, Br, OTs, OMs, aryl = 1-naphthyl, 2-naphthyl; X = Cl, 1-acenaphthenyl, 1-(2-methoxynaphthyl), 9-phenanthrenyl, 9-anthracyl) was synthesized and demonstrated to quantitatively cross-couple 2-methoxyphenyl dimethylsulfamate with methyl 4-(5,5-dimethyl-1,3,2-dioxaborinane-2-yl)benzoate at 23 °C in dry THF in the presence of K3PO4(H2O)3.2 in less than 60 min. Lower or higher amounts of H2O in K3PO4 and as received THF mediate the same transformation in a maximum three times longer reaction time.
- Jezorek, Ryan L.,Zhang, Na,Leowanawat, Pawaret,Bunner, Matthew H.,Gutsche, Nicholas,Pesti, Aleksander K. R.,Olsen, James T.,Percec, Virgil
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p. 6326 - 6329
(2015/02/19)
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