2801-86-7Relevant academic research and scientific papers
The tantalum-catalyzed carbozincation of 1-alkenes with zinc dialkyls
Sultanov, Rifkat M.,Samoilova, Elena V.,Popod'Ko, Natal'Ya R.,Sabirov, Denis Sh.,Dzhemilev, Usein M.
, p. 23 - 29 (2015/02/19)
The TaCl5-mediated reaction between monosubstituted alkenes and Et2Zn affords 3-(R-substituted)-n-butylzincs in high yield (up to 92%) and regioselectivity. Organozinc reagents bearing a longer alkyl chain (R = Prn, Bun, Amn, Hexn) react with 1-alkenes in the presence of TaCl5 as the catalyst to give two types of organozinc compound having iso-alkyl structure. The probable mechanism of the carbozincation reaction implies the formation of β-substituted and β,β'-disubstituted tantalacyclopentanes as the key intermediates. The thermodynamic probability of the mechanistic elementary stages for the ethylzincation of terminal alkenes has been estimated using DFT PBE/SBK method.
Photochemistry of racemic and resolved 2-iodooctane. Effect of solvent polarity and viscosity on the chemistry
Gao, Fang,Boyles, David,Sullivan, Rodney,Compton, Robert N.,Pagni, Richard M.
, p. 9361 - 9367 (2007/10/03)
The photochemistry of racemic and resolved 2-iodooctane was examined in cyclopentane, methanol, and 2-methyl-2-propanol, media with differing polarities and viscosities. The photochemistry of racemic 2-iodooctane was also examined in the gas phase. The photochemistry of 2-deuterio- and 1,1,1-trideuterio-2-iodooctane in cyclopentane and methanol was also studied. The photoreactions in cyclopentane, 2-methyl-2-propanol, and the gas phase occurred exclusively through homolytic reactions, while in methanol, they occurred predominantly (> 53%) through heterolytic reactions. By comparing the disappearance of the optically active substrate with its loss of optical activity, F, the fraction of the initially formed radical pair (RP) or ion pair (IP) resulting in product was determined for the three solvents. Because F contains contributions of both escape of the partners in the RP or IP into the bulk of the solvent and reaction within the RP or IP to yield products other than the substrate, there was no correlation between F and solvent viscosity. The F values will be valuable in assessing the photochemistry of 2-iodooctane in the same media with circularly polarized light.
Absolute rate constants for the addition of atomic hydrogen to monosubstituted and trisubstituted olefins
Tanner, Dennis D.,Zhang, Liying,Kandanarachchi, Pramod
, p. 11319 - 11324 (2007/10/03)
A mechanism is established for the formation of the products resulting from the solution phase regioselective addition of atomic hydrogen to 1-methylcyclohexene. From this data and new data for the reactions of 1-octene, the absolute rates and activation parameters for the addition of hydrogen atom to an olefin can be extracted. A method was established to determine the absolute rate of addition of a hydrogen atom to a terminal olefin in the solution phase. The addition rate constants, ka (25°C), to 1-octene [ka = (4.2 ± 3.6) × 109 M-1 s-1] and 1-methylcyclohexene [ka = (4.6 ± 0.8) × 106 M-1 s-1, -78°C] are found to be in reasonable agreement with the published values for the vapor phase rate of addition to ethylene. The large rate constants are supported by the observation that the activation parameters (Ea = 5.3 ± 2.9 kcal/mol and log A = 14 ± 3.5 M-1 s-1 for 1-octene) are consistent with the values expected for this fast reaction.
Formation of three-membered rings by SHi displacement. Reverse of cyclopropyl ring opening
Tanner, Dennis D.,Zhang, Liying,Hu, Li Qing,Kandanarachchi, Pramod
, p. 6818 - 6824 (2007/10/03)
The general methods, photoinitiated or peroxide-initiated free radical chain additions of halomethanes to olefins, yield 1,2-addition products at temperatures ranging from 20 to 100°C. At lower temperatures, -42 to -104°C, a competitive reaction, subsequent to the addition of CCl2X., yields alkylcyclopropanes. The reactions of 1-octene or 1-hexene and 1-methylcyclohexene with atomic hydrogen carried out in the presence of several transfer agents (CCl4, CCl3Br, CCl2Br2) initiate a radical chain addition of CCl2X. and yield cyclized materials resulting from the SHi displacement of halogen by a carbon-centered radical. The radical displacement of a halogen on carbon, the reverse of homolytic displacement on cyclopropyl carbon, is dominant at low temperatures. The rate constants for cyclization (kc) vs transfer with halomethane (kt) showed isokinetic temperatures of -46°C (CCl4, 1-hexene); -35°C (CCl4, 1-methylcyclohexene). The isokinetic temperatures for the reactions of the two substrates carried out in the presence of BrCCl3 were calculated as -204 °C (1-octene) and -109°C (1-methylcyclohexene).
Regioselective addition of atomic hydrogen to olefins. Reversible 1-methyl-5-hexenyl radical cyclization in the solution-phase hydrogenation
Tanner, Dennis D.,Zhang, Liying
, p. 6683 - 6689 (2007/10/02)
The solution-phase reactions of microwave-generated hydrogen atoms with terminal olefins is regioselective. Since addition is to the terminal end of the olefin, the reaction yields a secondary radical which undergoes either reaction with molecular or atomic hydrogen, disproportionation, combination, or addition to another olefin, and in the case of hydrogen atom addition to 1,6-heptadiene, cyclization. The cyclized radicals are formed reversibly, and the final product mixture contains only minor amounts of cis-1,2-dimethylcyclopentane (the product of kinetic control) while the major cyclized product is methylcyclohexane. Although an equilibrium mixture could not be obtained, the dimethylcyclopentyl and 3-methylcyclohexyl radicals were shown to be formed reversibly.
Regioselective and Diastereoselective Alkyl-Alkene and Alkene-Alkene Coupling Promoted by Zirconocene and Hafnocene
Swanson, Douglas R.,Rousset, Christophe J.,Negishi, Ei-ichi,Takahashi, Tamotsu,Seki, Takashi,et al.
, p. 3521 - 3523 (2007/10/02)
The reaction of Cp2Zr(CH2CH2R1)2 with a monosubstituted terminal alkene (H2C=CHR2) can produce, in a highly regio- and diastereoselective manner, zirconacyclopentane derivatives; the trans-3,4-disubstituted derivatives may be formed to the extents of >98percent in cases where both R1 and R2 are alkyl, while the trans-2-aryl-4-alkyl derivatives may be formed to the extents of >98percent in the coupling between a monoalkyl-substituted olefin and styrene or its derivative.
Electrochemical Reduction of 2-Iodooctane and 2-Bromooctane at Mercury Cathodes in Dimethylformamide
Mbarak, Mohammad S.,Peters, Dennis G.
, p. 3397 - 3403 (2007/10/02)
In dimethylformamide containing tetraalkylammonium perchlorates, a pulse polarogram for 2-iodooctane exhibits a pair of waves of identical height, attributed to stepwise reduction to the sec-octyl radical and carbanion, respectively.In contrast, 2-bromooc
