6708-17-4Relevant articles and documents
A structure-activity study of Ni-catalyzed alkyl-alkyl kumada coupling. Improved catalysts for coupling of secondary alkyl halides
Ren, Peng,Vechorkin, Oleg,Von Allmen, Kim,Scopelliti, Rosario,Hu, Xile
supporting information; experimental part, p. 7084 - 7095 (2011/06/26)
A structureactivity study was carried out for Ni catalyzed alkylalkyl Kumada-type cross coupling reactions. A series of new nickel(II) complexes including those with tridentate pincer bis(amino)amide ligands (RN2N) and those with bidentate mixed amino-amide ligands (RNN) were synthesized and structurally characterized. The coordination geometries of these complexes range from square planar, tetrahedral, to square pyramidal. The complexes had been examined as precatalysts for cross coupling of nonactivated alkyl halides, particularly secondary alkyl iodides, with alkyl Grignard reagents. Comparison was made to the results obtained with the previously reported Ni pincer complex [( MeN2N)NiCl]. A transmetalation site in the precatalysts is necessary for the catalysis. The coordination geometries and spin-states of the precatalysts have a small or no influence. The work led to the discovery of several well-defined Ni catalysts that are significantly more active and efficient than the pincer complex [(MeN2N)NiCl] for the coupling of secondary alkyl halides. The best two catalysts are [(HNN)Ni(PPh3)Cl] and [(HNN)Ni(2,4-lutidine)Cl]. The improved activity and efficiency was attributed to the fact that phosphine and lutidine ligands in these complexes can dissociate from the Ni center during catalysis. The activation of alkyl halides was shown to proceed via a radical mechanism.
Radiolysis of Cyclooctane with γ-Rays and Helium Ions
Wojnarovits, Laszlo,LaVerne, Jay A.
, p. 8014 - 8018 (2007/10/02)
Iodine scavenging techniques have been used to examine the role of the cyclooctyl radical in the radiolysis of cyclooctane with γ-rays and with 5-20-MeV helium ions.In γ-radiolysis about 70percent of the total yield of 6.6 cyclooctyl radicals/100 eV are scavenged with E-4 M iodine, which agrees well with other studies on cycloalkanes that show most of the radicals produced in these systems react in the bulk medium at times longer than 1 μs.However, it is found that 2.5 radicals/100 eV (38percent) are produced by H atom precursors as copmpared to a value of 1.5 cyclohexyl radicals/100 eV (25percent) in cyclohexane.With 10-MeV helium ions (average LET of 106 eV/nm), only 8percent of the cyclooctyl radicals survive longer than a few microseconds due to the increased initial radical concentration in the helium ion track.The yield of the cross-bridged product bicyclooctane (pentalane) was found to be independent of iodine concentration up to 0.03 M with both types of radiation.However, the pentalane yield found with 10-MeV helium ions was only one-third of that found in γ-radiolysis.The most likely reason for this result is the decreased yield of singlet-state formation due to the enhanced probability of cross combination reactions of electron-cation pairs in the high-density region of the helium ion track.
Alkane Functionalization on a Preparative Scale by Mercury-Photosensitized Cross-Dehydrodimerization
Brown, Stephen H.,Crabtree, Robert H.
, p. 2946 - 2953 (2007/10/02)
Alkanes can be functionalized with high conversions and in high chemical and quantum yields on a multigram scale by mercury-photosensitized reaction between an alkane and alcohols, ethers, or silanes to give homodimers and cross-dehydrodimers.The separation of the product mixtures is often particulary easy because of a great difference in polarity of the homodimers and cross-dimers.It is also possible to bias the product composition when the ratio of the components in the vapor phase is adjusted by altering the liquid composition.This is useful either to maximize chemical yield or to ease separation by favoring the formation of the most easily separated pair of compounds.The mechanistic basis of the reaction is discussed and a number of specific types of syntheses, for example of 2,2-disubstituted carbinols, are described in detail.The selectivity of cross-dimerization is shown to exceed that for homodimerization and reasons are discussed.Relative reactivities of different compounds and classes of compound are MeOHp-dioxanecyclohexane1,3,5-trioxacyclohexaneethanolisobutaneTHFEt3SiH.The observed selectivities generally parallel those for homodimerization, reported in the preceding paper, but certain differences are noted, and reasons for the differences are proposed.The bond-dissociation energy of Et3SiH is estimated from the reactivity data to be 90 kcal/mol.Eleven new carbinols are synthesized.
