- Generation and EPR Spectroscopy of the First Silenyl Radicals, R2C=Si.?R: Experiment and Theory
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The first two persistent silenyl radicals (R2C=Si.?R), with a half-life (t1/2) of about 30 min, were generated and characterized by electron paramagnetic resonance (EPR) spectroscopy. The large hyperfine coupling constants (hfccs) (a(29Siα)=137.5–148.0 G) indicate that the unpaired electron has substantial s character. DFT calculations, which are in good agreement with the experimentally observed hfccs, predict a strongly bent structure (?C=Si?R=134.7–140.7°). In contrast, the analogous vinyl radical, R2C=C.?R (t1/2≈3 h), exhibits a small hfcc (a(13Cα)=26.6 G) and has a nearly linear geometry (?C=C?R=168.7°).
- Pinchuk, Daniel,Kratish, Yosi,Mathew, Jomon,Zborovsky, Lieby,Bravo-Zhivotovskii, Dmitry,Tumanskii, Boris,Apeloig, Yitzhak
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- Asymmetric fluoro-alkynyl mercurials: The synthesis and solid state structures of RHgC=CCF3 (R = Ph, Fc)
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The fluoro-alkynyl mercurials RHgC=CCF3 (R = Ph, Fc) have been prepared, from the respective organomercurihalides and LiC=GCF3, and are the first examples of such materials to be studied crystallographically. These studies have revea
- Brisdon, Alan K.,Crossley, Ian R.,Pritchard, Robin G.
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p. 5487 - 5490
(2008/10/09)
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- tert-Butylation of α,β-unsaturated nitriles by tert-butylmercury halides in the presence of iodide ion
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Iodide ion promotes the free radical addition of t-BuHgI to acrylonitrile to form t-BuCH2CH(CN)HgI. A facile reaction of the adduct 1-cyanoalkyl radical with t-BuHgI2- is indicated. Further promotion is observed in the pre
- Russell, Glen A.,Chen, Ping,Yao,Kim
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p. 5967 - 5972
(2007/10/02)
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- tert-butylation of pyridines, quinolines, and isoquinolines by tert-butylmercury halides
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Photolysis of tert-butylmercury halides with pyridinium or quinolinium salts leads to alkylation via the intermediacy of adduct radical cations. With simple pyridines or the 2-adducts from quinolines, the radical cations readily lose a proton to form a substituted pyridinyl radical which is easily oxidized by the alkylmercury halide. Addition of t-Bu? at the 4-position of the quinolinium ions, the 1-position of the isoquinolinium ions, or the 9-position of the acridinium ions, yields in the presence of KI the dihydro derivatives formed via electron transfer to the adduct '? radical cation from I- or its ate-complex with the tert-butylmercury halide. A similar reductive alkylation is observed for the radical cations formed by the addition of t-Bu? to the β-position of the 4-vinylpyridinium ion or to the N-methylated cations derived from pyridine-3,4-dicarboximide, acridine, quinaldine, or isoquinoline. Competition between substitutive (oxidative) and additive (reductive) alkylation reflects the ease of proton loss from the intermediate adduct radical cation. Because of reversibility in adduct formation and variable rates of deprotonation of the adducts, yields of substitutive alkylation products are often not a true measure of the selectivity in the initial radical addition step. 4-tert-Butyl-1,4-dihydro-2-methylquinoline can be isolated from the photolysis of quinaldine with t-BuHgCl in the presence of KI/PTSA, methylated at C-3 by methyl iodide during the tert-butylation reaction, reduced by NaBH4 upon workup, or oxidized to the quinoline at long reaction times. 4-tert-Butyl-1,4-dihydroquinoline reacts rapidly in the presence of PTSA and t-BuHgCl to form 2,4-di-tert-butyl-1,2,3,4-tetrahydroquinoline while 4-/er/-butyl-2-chloro1,4-dihydroquinoline is readily hydrolyzed to form the amide. Although 1 -tert-butyl-1,2-dihydro-3-methylisoquinoline is isolable, 1 -tert-butyl-1,2-dihydroisoquinoline reacts via the iminium ion to form 1,3-di-tert-butyltetrahydroisoquinoline and the de-tert-butylated product 3-tert-butyl-3,4-dihydroisoquinoline. De-tert-butylation with aromatization is also observed upon photolysis of 4-tert-butyl-3,4-dihydro-2,3-dimethylquinoline with t-BuHgCl.
- Russell, Glen A.,Rajaratnam, Rajine,Wang, Lijuan,Shi, Bing Zhi,Kim, Byeong Hyu,Yao, Ching Fa
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p. 10596 - 10604
(2007/10/02)
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- Electron-transfer processes. 43. Attack of alkyl radicals upon 1-alkenyl and 1-alkynyl derivatives of tin and mercury
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Alkyl radicals, obtained by reaction of Bu3Sn? or ClHg? with alkylmercury halides, will undergo regioselective and in some cases stereospecific substitution by a free radical chain addition-elimination mechanism with 1-alkenylstannanes or -mercurials. The chain reaction is also observed for 1-alkynyl derivatives and in the photostimulated demercuration of mixed alkyl and 1-alkenyl- or 1-alkynylmercurials. Chain propagation with alkyl radical formation is also observed to occur in the reactions of β-eliminated ClHg? with Grignard reagents in PhH-THF solution. In competitive reactions of Bu3Sn? or ClHg? with pairs of alkylmercury chlorides, it is observed that a tert-butylmercurial is >1000 times more reactive than a n-butylmercurial, suggesting a concerted dissociate electron-transfer process not involving the intermediacy of RHg? species.
- Russell, Glen A.,Ngoviwatchai, Preecha,Tashtoush, Hasan I.
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p. 696 - 702
(2008/10/08)
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- Synthesis and characterization of tert-butyl(tert-butyltellurio)mercury(II)
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The compound (t-Bu)HgTe(t-Bu) was prepared by the reaction of (t-Bu)HgCl with (t-Bu)TeLi in tetrahydrofuran solution at -5°C. The yellow crystalline light-sensitive solid is stable in an inert atmosphere but decomposes in solution at 20°C. It gives a strong (M + 1)+ peak in the methane chemical ionization mass spectrum. 1H, 13C, 125Te, and 199Hg NMR spectra (toluene, -15°C) show two distinct tert-butyl groups, one type on mercury (δHg = -883 vs. dimethylmercury) and one type on tellurium (δTe = 339 vs. dimethyl telluride), with couplings 1JTe-C = 390, 1JHg-C = 1285, 2JHg-C = 17, 3JTe-C-C-H = 20, and 3JHg-C-C-H = 196 Hz. The far-infrared spectrum is interpreted in terms of Hg-Te stretching at 151 cm-1, C-Hg-Te and C-Te-Hg bending at 239 and 224 cm-1, and Te-C and Hg-C stretching at 491 and 511 (shoulder) cm-1. The ultraviolet spectrum (pentane solution) exhibits bands at 365 (shoulder, log ε = 2.6), 295 (shoulder, log ε = 3.6), and 227 nm (log ε = 4.7). Nuclear magnetic resonance, far-infrared, and ultraviolet spectra are also reported for (t-Bu)2Hg and (n-Bu)2Te.
- Harris, Daniel C.,Nissan, Robin A.,Higa, Kelvin T.
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p. 765 - 768
(2008/10/08)
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