106032-42-2Relevant academic research and scientific papers
A general study of [(η5-Cp′)2Ti(η 2-Me3SiC2SiMe3)]-catalyzed hydroamination of terminal alkynes: Regioselective formation of Markovnikov and anti-Markovnikov products and mechanistic explanation (Cp′=C (5)H(5), C(5)H(4)Et, C(5)Me(5))
Tillack, Annegret,Jiao, Haijun,Castro, Ivette Garcia,Hartung, Christian G.,Beller, Matthias
, p. 2409 - 2420 (2004)
A general study of the regioselective hydroamination of terminal alkynes in the presence of [(η5-Cp)2Ti(η2-Me 3SiC2SiMe3)] (1), [(η5-CpEt) 2Ti(η2-Me3SiC2SiMe3)] (CpEt= ethylcyclopentadienyl) (2), and [(η5-Cp*) 2Ti(η2-Me3SiC2SiMe3)] (Cp=pentamethylcyclopentadienyl) (3) is presented. While aliphatic amines give mainly the anti-Markovnikov products, anilines and aryl hydrazines yield the Markovnikov isomer as main products. Interestingly, using aliphatic amines such as n-butylamine and benzylamine the different catalysts lead to a significant change in the observed regioselectivity. Here, for the first time a highly selective switch from the Markovnikov to the anti-Markovnikov product is observed simply by changing the catalyst. Detailed theoretical calculations for the reaction of propyne with different substituted anilines and tert-butylamine in the presence of [(η5-C5H5)Ti(= NR)(NHR)] (R=4-C6H4X; X=H, F, Cl, CH3, 2,6-dimethylphenyl) reveal that the experimentally observed regioselectivity is determined by the relative stability of the corresponding π-complexes 10. While electrostatic stabilization favors the Markovnikov performance for aniline, the steric repulsive destabilization disfavors the Markovnikov performance for tert-butylamine.
