2801-86-7Relevant articles and documents
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.
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.
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.
